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TelevisionCircuit Description and Troubleshooting
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S
®
Training Manual
High Definition Television
Circuit Description and Troubleshooting Course: DTV-01
Table of Contents
Introduction HDTV Transmission Stream Introduction to MPEG-2 Compression Model KW-34HD1 - Normal Operation Inputs Overall Block SIGNAL PROCESS Video Block 1 Video Process A Video Process B Video Block 2 Digital Realty Creation MID - Multi Image Driver Video Process C Video Block 3 Video Process D On Screen Display Video Process E Screen Voltage Control 29 31 33 35 37 41 43 45 47 49 51 53 1 3 9 19 21 25 POWER SUPPLY Power Supply Block Standby Power Converter 2 Overall Protection Block D Board Protection Block Protection Circuit 1 Protection Circuit 2 Protection Circuit 3 Protection Circuit 4 DEFLECTION Vertical Deflection Horizontal Deflection Block Horizontal Drive Horizontal Driver Horizontal Output PWM 1 Horizontal Output PWM 2 Pincushion Correction Picture Tilt Circuit Dynamic Focus Block 85 89 91 93 97 101 105 109 113 55 53 61 67 71 73 75 77 81
Dynamic Focus 1 - B+ Mfg. Dynamic Focus 2 - Location Dynamic Quadrapole Focus Appendix
Set-Back Box Picture Size Modes Board Replacement Service Mode Display
117 121 125
i iii iv vi
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Introduction
TV Transmission Formats
Standard Definition/High Definition
Picture resolution is commonly measured in pixels or lines. The number of pixels is the number of black to white brightness changes possible on the screen first in a horizontal, then in a vertical row (e.g. 960x480). CRT manufacturing tolerances limits the number of pixels possible. This is a common resolution specification in a computer monitor CRT. In a TV broadcast, the studio camera is the limitation to higher resolution. The picture scanned by the camera is segmented by pixels similar to the viewer's CRT. The greater the number of pixels in the horizontal and vertical row, the greater the resolution. This will be the current resolution limitation as the USA makes the transition toward high definition digital TV. In a TV transmission, the ability of a signal voltage to quickly change from low to high and to produce a dark to white transition is comparable to a pixel. This is not a limitation in the transmission format, but the number of lines transmitted is and is used as a resolution measurement in transmissions. The number of lines transmitted in the current USA NTSC format is 525. This is considered a standard definition (SD) transmission. A standard definition (SD) transmission of 525 lines can be transmitted in the analog or digital mode. A higher definition (HD) transmission can be transmitted only in the digital (DTV) mode. ¨ SDTV or SD Standard definition is the current 525 lines of resolution transmitted, but only 480 of those lines are viewable. SD can be sent as an NTSC analog or digital (DTV) transmission. HDTV or HD A high-definition transmission contains 720 or more horizontal lines. HD is transmitted only in a digital format. DTV A digital TV transmission refers only to the digital encoding of the picture signal that may contain either a high (HD) or low (SD) resolution picture. The digital picture is not viewable on an analog TV without a "decoder box".
Digital Transmission Formats
There are 18 approved digital transmission formats. The first six offer HD signals in a 16x9 aspect ratio. The remaining 12 formats are SD signals in progressive (p) or interlaced (i) scan. Although not high resolution, they offer significant improvements over the NTSC analog signal.
18 Digital Transmission Formats Resolution 1. 1920x1080 2. " 3. " 4. 1280x 720 5. " 6. " 7. 704x 480 8. " 9. " Aspect Ratio 16:9 16:9 16:9 16:9 16:9 16:9 16:9 16:9 16:9 Frames 30 i 30 p 24 p 60 p 30 p 24 p 60 p 30 i 30 p Resolution 10. 704x 480 11. " 12. " 13. " 14. " 15. 640x 480 16. " 17. " 18. " Aspect Ratio 16:9 4:3 4:3 4:3 4:3 4:3 4:3 4:3 4:3 Frames 24 p 60 p 30 i 30 p 24 p 60 p 30 i 30 p 24 p
A standard definition transmission permits space for another digital video stream to coexist on the same frequency (channel). Consequently a station can have more than one program stream on a digital channel. The maximum number is not known at this time.
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How to use this book for servicing
When encountering this TV set for servicing there are several things you need to know. Below is a list of the necessary servicing items and where to locate them:
Servicing Needs Information 1. Hookup / Operation / Normal Operation 2. External HDTV set-back box indicator lights 3. Location of power handling parts and fuses 4. Standby light indication message & board determination 5. Shutdown troubleshooting plan 6. Power Supply, Deflection, Video Selection and Signal Flow Circuitry 7. Focus Circuitry 8. Dynamic Convergence adjustments Location First document in this training manual (Normal Operation) Appendix Service manual / visual inspection of heat sinks Service manual and Protection Block document Protect Circuitry 3 & 4 Circuitry in this training book. See table of contents. Circuitry in this training book Service manual page 27 (same as in training manual supplement) Notes on using the service mode follow this chart. A list of register names are in the service manual. Training manual supplement
Service Mode Adjustment Notes
Because of this TV's complexity, the following precautions should be noted while making service adjustments for convergence, video level, size, and white balance or positioning: 1. The numerous service mode registers are usually grouped by ICs for easy access. Use the remote's #2 and #5 button to change IC groups. Then you can move from register to register with the #1 and #4 buttons. 2. Each register that controls the picture's size, deflection and position (on pages 45-47 of the service manual) has seven sets of adjustment data, one for each of the seven picture size modes. These settings do not interact. Enter the service mode, adjust the TV during that picture size, and store it.
Seven Picture Size Modes NTSC or SD DTV 1. Normal 4:3 aspect ratio 2. Full 16:9 aspect ratio 3. Zoom 4. Wide Zoom 5. Caption (Top & bottom pix compressed) HDTV 6. HDTV Full 7. HDTV Twin View
9. Adjustments after tube replacement
1. Some registers are duplicated under different groups for ease of adjustments. These duplicated registers have the same name. Changing the register data at one location causes the data to change at the other location as well. 2. Save adjustments often. Changing registers will hold the new data, but changing picture sizes (zoom, full, caption, etc) will instantly lose any unsaved data that was just held. 3. There are separate contrast, color level, and hue adjustments for: ¨ The main picture ¨ The HDTV picture ¨ Each twin view picture They are adjusted for equal levels as you switch modes. This is so the picture is not brighter in one mode than another.
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HDTV Transmission Data Stream
Transmission Block
The National Television Systems Committee (NTSC) was a group that created the analog TV standard. The purpose of the Advanced Television Systems Committee (ATSC) is to similarly set the digital TV standard. The primary objective was to create a transport stream in a transmission scheme that would fit in the current 6 MHz bandwidth channel. For expansion and versatility, space in the transport stream was made for additional service data. Using this transmission method, each station can broadcast more than one digital program simultaneously on the same 6 MHz channel by compromising picture resolution. In order to understand how a digital picture quality signal is sent within the 6 MHz bandwidth, the block diagram of the transmission scheme is needed first, to explain the structure. The HDTV Transmission Block consists of two parts. The Transport Packet Generation part multiplexes the compressed video, audio, and additional digital data into a single stream. The VSB Transmission part scrambles the data to reduce recovery errors, groups the data, adds sync data, and transmits the information.
VSB Transmission
The Vestigial Sideband Transmission part of the block takes the transport packets from the Data Multiplexer and performs the following: · Scrambles the data · Groups the data · Adds sync
Data scrambling
The Data Randomizer block, the Reed Solomon Encoder block and the Data Interleaver block all scramble the data but in different areas. Scrambling the data is done for reliable recovery of lost, damaged, or missing data. Scrambling scatters the data so it is no longer in the normal 1, 2 3, 4, 5, 6 linear sequence. For example the scrambled data may have a packet sequence that looks like this: 3, 18, 33, 11, 4, 52, 89, 7 etc. During the transmission if a large loss of data packets 11, 4, 52 occurred, the lost pieces are not as significant as if sequential data packets 4, 5, 6 were lost. This is because at the decoder where the packets are returned to the linear order, data packets 11, 4, & 52 are in different places. The large loss actually consists of smaller losses that can be interpolated from the remaining adjacent data.
The Transport Packet Generation
When both video and audio analog signals are converted to a digital format, a huge bit stream is output. Without compression, this digital signal could not be transmitted within the 6 MHz boundary. The video bit stream reduction is accomplished using four cohesive methods within the Motion Picture Experts Group (MPEG) encoder block. Audio bit reduction is performed in the Dolby Ò developed (AC-3) encoder block. The additional services data may contain information pertaining to the TV program or unrelated data such as Internet or computer data. TV program related information is in a structure called Program and System Information Protocol (PSIP). It contains additional sync, real time, station ID, alternate channel number display and more. The video and audio output from the encoders is multiplexed with additional services data into a single bit stream by the Data Multiplexer. The data output is in groups called transport packets. They are applied to the VSB Transmission part of the block.
Groups the Data
The Trellis Encoder works with the VSB modulator to reduce transmission bandwidth. The encoder takes a stream of bits and groups them into 3 bit words called symbols. The purpose is to ultimately reduce the bandwidth by reducing the frequency.
Sync is added
Segment sync and field sync added to the transport packets in the multiplexer. The Segment sync marks each transport packet. The field sync identifies a group of transport packets. The multiplexer's data output is called a VSB data frame.
VIDEO
MPEG COMPRESSION ENCODER
DATA RANDOMIZER
SEGMENT SYNC
FIELD SYNC AUDIO AC-3 COMPRESSION ENCODER DATA MULTIPLEXER REED SOLOMON ENCODER
MULTIPLEXER (VSB DATA FRAME CREATED)
RF UP CONVERTER
ADDITIONAL SERVICES DATA
DATA INTERLEAVER
TRELLIS ENCODER
VSB MODULATOR
TRANSPORT PACKET GENERATION
VSB TRANSMISSION
HDTV TRANSMISSION BLOCK
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Data Process - Transport Packet Generation
After MPEG and AC-3 compression, the audio and video data is multiplexed with additional services data into a 188-byte transport packet. The transport packet is output at a 19.4Mbits/sec data rate. The packet consists of a link header and a payload.
VIDEO
MPEG COMPRESSION ENCODER
AUDIO
AC-3 COMPRESSION ENCODER
DATA MULTIPLEXER
DATA RATE 19.4Mbps
DATA RATE = 188 bytes* 8bits/byte * 626segments/frame * 20.66 frames/sec 188 BYTES
Link Header
Each packet is preceded by a link header that contains: · Sync - Identifies the beginning of the packet and a sample of a 27Mhz clock. · Continuity Counter or Error Control Numbers each packet · Transport Scrambling Control - Identifies if this packet is scrambled. · Packet ID (PID) Links related and marks duplicated (important) packets. Marks the location of the unscrambling packet (if any).
ADDITIONAL SERVICES DATA
LINK HEADER (4 BYTES)
PAYLOAD (184 BYTES)
TRANSPORT PACKET
TRANSPORT PACKET GENERATION
Payload
The payload consists of 184 Bytes of multiplexed audio, video and additional services data.
Data Process VSB Transmission
Data Randomizer
The construction of the VSB data frame begins at the Data Randomizer. This block scrambles only the payload data in a set pattern so it can be unscrambled at the decoder.
INPUT DATA RATE = 188 bytes* 8bits/ byte * 626segments/frame * 20.66 frames/sec 832 SYMBOLS INPUT DATA RATE 19.4Mbps NOTE : FRAME = (77.3us * 626 SEGMENTS) = 48.38ms THEREFORE, THERE ARE 20.66 FRAMES/S FIELD SYNC #1
188 Bytes SEGMENT SYNC
DATA RANDOMIZER
S E G M E N T S Y N C
DATA + OVERHEAD
313 SEGMENT S
FIELD SYNC #2
Reed - Solomon Decoder
This decoder scrambles the entire transport packet except for the early sync in the link header. It adds 20 parity bytes for error correction to insure recovery. The transport packet has been increased to 208 Bytes.
REED SOLOMON ENCODER (Adds 20 Bytes) 208 Bytes
FIELD SYNC
MULTIPLEXER (VSB DATA FRAME CREATED) 312 Bytes/ segment
DATA + OVERHEAD
313 SEGMENT S
RF UP CONVERTER
1 SEGMENT = 77.3us VSB DATA FRAME VSB MODULATOR
Data Interleaver
This block scrambles about 1/6 of a field of data (more than a single transport packet) in accordance to a preset pattern. The Data Interleaver basically adds no additional bits. 208 Bytes is output.
DATA INTERLEAVER
TRELLIS ENCODER
VSB TRANSMISSION
OUTPUT DATA RATE 32.28Mbps or 10.76Msymbols/sec
Trellis Encoder
The details of the Trellis Encoder data processing scheme will be explained later. To simplify the data structure understanding for now, the Trellis encoder adds additional bytes to the process and converts the incoming stream to 3 bit words, which represent 1 of 8 different levels. These 3 bit words are termed symbols. The details of the Trellis Encoder are beyond the scope of this manual but an overview is presented later.
188 BYTES OUTPUT DATA RATE = 3 bits/symbol * 832 Symbols/segment * 626segments/frame * 20.66 frames/sec LINK HEADER (4 BYTES) PAYLOAD (184 BYTES) TRANSPORT PACKET INPUT DATA RATE 19.4Mbps
SYNC 4 SYMBOLS (12 BITS)
828 SYMBOLS
Multiplexer
The Multiplexer combines the symbols with segment sync to from what is defined as a segment. Each segment contains four symbols of segment sync plus 828 symbols of payload data. Therefore each segment contains the equivalent of a scrambled transport packet + sync. 312 segments represent approximately a field of digital data. The multiplexer adds an additional field sync to the beginning of the 312 segments, making a field equal to 313 segments. Two fields equals a frame so 626 segments = a complete Vestigial Sideband (VSB) data frame. This frame is sent to the VSB modulator for transmission. The Data Structure diagram shows the VSB Frame information sent in segments. Each segment contains sync, data and overhead
S Y FIELD SYNC N #1 C S DATA Y & N OVERHEAD C
312 BYTES = 832 SYMBOLS = SEGMENT
S DATA Y & N OVERHEAD C
S Y FIELD SYNC N #2 C
S DATA Y & N OVERHEAD C FIELD = 313 SEGMENTS
S DATA Y & N OVERHEAD C
FIELD = 313 SEGMENTS FRAME = 626 SEGMENTS
OUTPUT DATA RATE 32.28Mbps or 10.76Msymbol s/sec
DATA STRUCTURE
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Trellis Encoding Scheme
The Trellis Encoder works with the VSB modulator in a scheme to reduce bandwidth by 1/3. The encoder converts the incoming stream into 3-bit word groups. The 3 bit words are assigned in a mapping table that is designed to reduce transitions (bandwidth). Each 3-bit word group is called a symbol. The VSB modulator converts each 3-bit symbol to a corresponding DC level for transmission. Three bit symbols can designate up to 23 = 8 analog levels. For example at the modulator input of the Trellis Scheme diagram, the data is 110, 111, 101, 010, 111, 000. That corresponds to a DC level of +5, +7, +3, -3, and +7, as shown at the modulator output. By replacing the 3-bit word with a single DC voltage, the digital information sent to the AM transmitter is reduced by 1/3.
DATA STREAM INTO TRELLIS ENCODER 01001101110100100111100100101010101
TRELLIS ENCODER
DATA STREAM OUT OF TRELLIS ENCODER 000 111 001 001 011 000 111 010 101 111 110
DATA STREAM INTO ENCODER UNDERGOES CONVERTION USING A MAPPING SCHEME TO 3 BIT WORD GROUPS CALLED SYMBOLS. THESE SYMBOLS ARE USED BY THE VSB MODULATOR
DATA STREAM OUT OF TRELLIS ENCODER 000 111 001 001 011 000 111 010 101 111 110
VSB MODULATOR
SINCE THE SYMBOLS ARE 3 BIT, THEY CAN ONLY REPRESENT ONE OF 8 POSSIBLE LEVEL COMBINATIONS. THE VSB MOD CONVERTS THE SYMBOLS TO LEVELS.
111 110 101 100 011 010 001 000
+ 7 + 5 + 3 + 1 -1 -3 -5 -7
TRELLIS SCHEME
Trellis Encoder B/W Reduction Scheme
To understand how the Trellis Encoder reduces bandwidth by 1/3, an example using the worse case highest frequency digital signal is shown. The worse case signal is a waveform that is alternating between digital 0 and 1. Twelve of these alternating bits are shown, occurring in one second (data rate = 12 bits/sec). By examining this waveform you can see that two bits is the equivalent of one cycle. Therefore the data rate of 12 bits/sec is equivalent to 6 cycles/sec (Hz). The Trellis Encoder manufactures the 3 bit symbols and the VSB modulator translates each symbol into a single DC level for transmission. The worst case transmission is also when the DC level is alternating between low and high. However since 3 bits is represented by a single DC level after the modulator, the input data rate of 12 bits/sec results in a transmission of only 2 cycles/sec instead of 6 cycles/sec. This means that a data rate of 32.28Mbps is reduced by 1/3 to 10.76 Mbps using the Trellis Encoder scheme. Since two bits are the equivalent of one cycle, the data rate is halved to arrive at the equivalent frequency. Therefore the audio, video and additional services data will have a maximum frequency of to 10.76 Mbps /2 = 5.38 MHz. This is within the current 6 MHz TV channel bandwidth.
TYPICAL DATA STREAM IN A WORST CASE SCENARIO WHERE DATA IS TRANSITIONING BETWEEN 1 AND 0 ALL THE TIME AS OPPOSED TO RANDOM. 12 BITS/SEC DATA RATE = 12BITS/SEC EQUATES TO 6 CYCLES/SEC FREQUENCY
ONE CYCLE TRELLIS ENCODED DATA STREAM IN A WORST CASE SCENARIO WHERE DATA IS TRANSITIONING BETWEEN ONLY TWO LEVELS 111 AND 000 ALL THE TIME AS OPPOSED TO RANDOM.
NET EFFECT OF THE TRELLIS ENCODER IS REDUCTION OF TRANSMISSION FREQ BY A FACTOR OF 3, HENCE THE 32.28Mbps DATA RATE IS REALLY TRANSMITTED AT 10.76Mhz
DATA RATE = 12BITS/SEC EQUATES TO 2 CYCLES/SEC FREQUENCY
ONE CYCLE
TRELLIS ENCODER BW REDUCTION SCHEME
Nyquist it ~ 10.76Mhz / 2 = 5.38 Mhz
5.38 MHZ
6 MHZ
SPECTRAL BANDWIDTH
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Introduction to MPEG-2 Compression
MPEG stands for Motion Picture Experts Group, named after the committee that developed the standard.
Each sample we take of the video is represented by an 8 bit digital word which translates to 28 or 256 different levels of each component. Therefore, each pixel is made up of 3 components which can represent up to 28 (Y) X 28 (R-Y) X 28 (B-Y) = 224 (commonly known as 24 bit color)or 16 million colors.
Why Compress?
MPEG defines a compression scheme for Video which evolved from the need to transmit digital video on existing communication channels with limited bandwidth. In addition to the bandwidth issue there is an obvious storage one as well. Fastest Communication Channels ISDN Line T1 Line T3 Line Typical Bandwidth 144Kbps 1.5 Mbps 45 Mbps
Y
B-Y
One PIXEL
R-Y
The resolution or picture detail we require also plays an important role in our bandwidth and storage requirement. DVD uses a 720 Horizontal by 480 Vertical resolution or 720 pixels across times 480 rows or lines.
720 480
With a whopping 4.7 gigabytes of data capacity, DVD-Video would seem to have more than enough room for motion pictures. Unfortunately, digital video has an incredibly voracious appetite for storage. Raw or uncompressed Digital Video requires an enormous 252 Megabits/sec of bandwidth and approx 31 Mbytes per second of storage. 720x480 (Res.) X 8bits/sample X 30frames/sec X 3 Components To understand this figure, we need to understand video in its purest form. In summary we need to: - sample 3 components (Y, R-Y and B-Y) each of which is composed of 720 x 480 (350,000) pixels. - Represent each one by an 8 bit word (3 X 350,000 X 8 = 8,400,000bits). Therefore, each frame is made up of 8,400,000 bits. - Finally, we would need to display at 30 frames per second (30 X 8,400,000 =252,000,000 bits/sec or 252 Mbits/sec Bandwidth. To calculate the storage we simply divide the Bandwidth in bits by 8 bits per byte and we get 31.5Mbytes/sec Storage requirement. As illustrated, the requirement is enormous which paves the way for compression and MPEG.
Component Video
In its purest form, Video is made up of 4 components. - Luminance or Y which defines the brightness level and - Color which is made up of 3 components called R-Y, B-Y and G-Y. As it works out, we can mathematically calculate the 4th component (GY) from the others. Therefore, we only require 3 components for Video (Y, R-Y and B-Y). Y = (R-Y) + (B-Y) + (G-Y)
Compression Process
Compression of Video is accomplished via the following process. 1. Selective Sampling 2. Discrete Cosine Transform (DCT) 3. Predictive & Motion Encoding 4. Hoffman Encoding
4:2:2
Since the eye is less perceptive to color changes than to Luminance, significant reduction of data can be accomplished in the Sampling process if we sample the color components (R-Y and B-Y) half as much as the Luminance component (Y). The result is a 1/3 reduction or a bandwidth of 166Mbits/sec. Video sampled using this technique is represented by a 4:2:2 sampling structure. Y is sampled normally with R-Y and B-Y sampled half as much.
ONE PIXEL LINE 1 LINE 2 . . . . LINE 480
Selective Sampling
The number of times per second that you sample a signal is called its sampling frequency. In Audio, the sampling frequency is 44,000 samples/ sec which is approx 2 times the highest frequency in Audio (20,000 Hz). In contrast, Video is sampled at 4 times the highest frequency (13.5Mhz). Hence the term 4 in the sampling structure 4:4:4 representing the sampling ratio of Y, R-Y and B-Y respectively. Therefore, the same number of samples are taken of Y as they are of RY and B-Y.
Samples taken in the Horizontal direction up to 720 per Line
Y Y R-Y R-Y B-Y B-Y Y Y Y Y R-Y R-Y B-Y B-Y Y Y
Non Sampled components Illustrated as clear boxes
Signal
4:1:1
Consequently techniques such as the 4:1:1 further reduce color sampling to 1/4th of the Y component and compress by ½ or reduce bandwidth to 125Mbits/sec.
Time
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4:2:0
DVD takes it to another level by using a modified 4:2:2 sampling structure called 4:2:0. 4:2:0 samples R-Y half as much as Y and skips B-Y on the 1st line. However, on the next horizontal line, B-Y is sampled half as much as Y and R-Y is skipped. This routine is repeated effectively reducing the color components by another half achieving ½ compression or a 125Mbit/sec bandwidth. Through interpolation, the 4:2:0 is reconstructed into 4:2:2 without the extra bandwidth requirement.
The high frequency information consumes the most data real estate and is where we focus to compress in this next stage. The process of eliminating the imperceptible information is called Discrete Cosine Transform or DCT. The sampling process converts the information into digital data as described previously. Each digital picture frame is then sectioned off into 5400 blocks each consisting of 8 pixels wide X 8 pixels high.
1 of 5400 Blocks
ONE PIXEL LINE 1 LINE 2 LINE 3 LINE 4 . . . . LINE 480
Samples taken in the Horizontal direction up to 720 per Line
Y Y Y Y R-Y B-Y R-Y B-Y Y Y Y Y Y Y Y Y R-Y B-Y R-Y B-Y Y Y Y Y
Picture Frame
Non Sampled components Illustrated as clear boxes
8X8 Pixel Block
Discrete Cosine Transform After the Selective Sampling process is complete, the next step in the MPEG process is to remove very fine picture detail imperceptible to the human eye. It is imperceptible because it is typically masked by other picture content. In a Video Frame, the very fine picture details consist of high frequency information which are basically fast changing Luminance and Color content. In contrast, low frequency information are slow changing Luminance and Color content.
DCT transforms the 8X8 group of pixel values into frequency components. Although pixel values vary randomly in the 8X8 block, DCT re-positions low frequency components on the upper left corner and high frequency components on the lower right of the block. Through an additional numerical conversion process called "Quantization", frequency component values are assigned. High freq components are identified by the zero values (lower right) and low freq components by the larger values (upper left).
Data compression is accomplished by elimination of the high frequency components designated by the zeros.
Temporal Redundancy
Within Video scenes, there are many redundant frames. An example would be an anchor person reporting the news. With the exception of lip movement, the other portions of the frame remain unchanged over time. This type of redundancy over time is called "Temporal Redundancy". The first frame could be stored as the reference or non changing portions while remaining frames carry the lip motion information. This would eliminate the need to store several full frames. Frames using Temporal redundancy which predict information based on preceding frames are called "Inter-Frames" or Motion predicted Images.
8 X 8 Pixel Block LFreq 10 5 0 0 0 0 0 0 HFref 5 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 HFref 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Predictive & Motion Encoding
The next step in the MPEG process is termed "Predictive & Motion Encoding" and it takes advantage of both Spacial and Temporal redundancy to achieve compression.
I-Pictures
To begin the process of using Spacial and Temporal redundancy techniques in compression, we need a reference or a start frame which does not depend on previous or preceding frames. This start frame would make use of Spacial redundancy within itself and is termed an I picture.
Spacial Redundancy
Within a Frame, there are many redundant pixels. An example would be a blue sky. This type of redundancy within the Horizotal and Vertical plane of a frame is called "Spacial Redundancy". One pixel could be stored with information to repeat for the remaining pixels. This would eliminate the need to store every pixel in the frame. Frames making use of this technique are called "Intra-Frames". I pictures are Intra-Frames and have zero dependency on previous or preceding frames. They do however provide information to preceding frames. The other pictures types used by MPEG are called P-Pictures (Predictive) and B-Pictures (Bi-Directional). I Pictures carry the most amount of data content. They are 3 times the size of a P-Picture and 5 to 6 times the size of a B-Picture.
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P-Pictures
The P-Pictures are Predictive Encoded Images also known as InterFrames. As the name indicates, a P-Picture is a predicted Image based on previous I or P-Picture. The P-Picture is dependent on past Images to exist.
I or P Picture I or P Picture
B-Pictures
Predicted
by looking back at previous
I or P Pic And
P Picture
Future P Picture P-Picture
Predicted by looking back at previous I or P Pic
Information passed to generate P Picture
B-Pictures
The B-Pictures have Bi-directional dependency and are called BiDirectional Predicted Images. The B-Picture is also a predicted Image but it is based on prior I or P Pictures and preceding P-Pictures. B-Pictures are typically made up of motion information and carry the least amount of data.
I, P and B picture generation process
To clearly understand the relationship between the I, P and B pictures we need to understand how they are generated. 1. The start of an entirely new scene would require an I-Picture or a reference for other pictures to follow until the next I-Picture. - The information between the I-Picture and the next reference IPicture is called a GOP (Group of Pictures) which consist of one I and many P and B Pictures. - I-Pictures typically re-occur at 15 picture intervals. 1. Next, the first P-Pictures in the GOP is generated based on the IPicture. 2. In between the I and first P-picture, several B-Pictures are generated as necessary to convey motion information from the I to the first P-Picture. For this reason B-Pictures are dependent on past and future pictures. 3. Then the process repeats with the generation of second P-Picture which is now based on the first P-picture. And so on...
Hoffman Encoding
The last step in the MPEG process uses a statistical approach to compress the data further. The last process is called Hoffman Encoding. Basically, this process takes a look at the string of MPEG data and replaces it with information which allows regeneration. The best example is a string of eight "1's" {11111111} replaced by {1x8} which represents; repeat the 1 eight times.
I B B P GOP B B P I Time
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MPEG II vs- MPEG I The MPEG process described is common to both MPEG II and MPEG I thus, explaining the backward compatibility between the two. The main differences between MPEG II and I are: - MPEG II used in DVD uses a 720 x 480 resolution while MPEG I used in VIDEO CDs carries a resolution of 350 x 240. This difference alone accounts for a 75% reduction in data using MPEG I over MPEG II. - MPEG II compresses data to about 1/40 on average while MPEG I compresses data to about 1/140 on average. Therefore 250Mbit/s are reduced to 6.25Mbits/s on average using MPEG II. - MPEG II uses a variable rate compression while MPEG I uses a fixed rate. 350 x 240 = 84,000 pixels 720 x 480 = 350,000 pixels MPEG I represents 84,000/350,000 = 25% of MPEG II.
MPEG II additional information
MPEG II is a broad standard which encompasses many resolutions including HDTV. These variations in MPEG II are defined by Levels and Profiles. DVD is just one of the many profiles and levels defined by MPEG II called Main Profile at Main Level ( MP@ML).
The Bit Rate Fluctuates
For DVD, variable bit rate is a tremendous advantage. If the bit rate were fixed, it could not accommodate the changing needs of video scenes. Consider the fast-paced action of a football player, running for a touchdown as the camera pans past the crowd. Full of motion, this is an extremely demanding scene, one that requires the bit rate to be very high. Now picture the same football player after the game, sitting in a restaurant, talking to his girlfriend. Almost nothing in the scene moves, so the bit rate can be quite low. If DVD used a fixed bit rate, the system might fall short on the football scene. And it would definitely be wasting bits on the restaurant scene. DVD-Video accommodates both scenes by varying the bit rate. In fact, the maximum bit rate is 9.8 megabits per second which is nearly three times as high as the "average" rate. If DVD used a fixed rate, it would have to be at least 7 Mbps to maintain picture quality! At that rate, total recording time would be cut in half. So the goal of capturing a full-length movie on a 3-3/4-inch disc could not be realized. Variable bit rate is one of the key technologies that makes DVD possible. By the way, Video CD uses MPEG-1 to yield a fixed bit rate of 1.15 Mbps. The fixed rate and low number translate into the vast quality difference between DVD-Video and Video CD.
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24 Frames-per-Second Storage
In video, what appears to be a continuously moving image is actually a series of discrete still pictures, called frames. Every video frame consists of two interlaced "fields", each of which contains half the frame's scanning lines. A U.S.-standard video picture runs at roughly 30 frames per second. In contrast, movie file operates at 24 frames per second. So the movies you see on television, cable or videocassette have all had their frame rates converted by a special machine called a "telecine". The telecine converts the 24 film frames into video fields. However, video requires 30 frames or 60 fields and Film is 24. Telecine performs this process by converting 12 film frames to 24 fields (2 Fields/Film Frame) and another 12 film frames to 36 fields (3 Fields/Film Frame). It is kept seamless by converting one Film Frame to 2 Fields and the next one to 3. This cycle is repeated 2, 3, 2, 3 until the 60 fields have been completed. This Telecine process is called 2-3 Pull Down. To achieve maximum recording time, the DVD-Video disc is actually mastered in the original 24 film frame format. This reduces the video bit rate by 20%, even before MPEG-2 encoding. During playback, the DVD-Video player performs the 2-3 pull down function to generate a standard 30 frames per second video output.
NOTES
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19
Model KW-34HD1 - Normal Operation
These are normal operating conditions for Sony's first high Definition TV during power on/off and input selection conditions.
Power ON
Operation Plug in Power ON A Initial Step AC connection Master power ON button pressed Sounds Nothing 1. 2 Relays click immediately 2. Degaussing coil energized (humming sound) 3. TV audio 1 sec after relays click Visual Nothing 1. Front panel Standby light: 2. Blinking after relay click 3. Stops blinking in about 7 seconds when the picture appears. 4. OSD: Yellow characters "Please check DTV receiver connections" 1. Front panel Standby light: 2. Standby light starts blinking after relay click 3. Stops blinking in 7 seconds when the picture appears. 4. OSD reads in Yellow characters "Please check DTV receiver connections". Picture goes dark All lights out Picture goes dark Standby light comes ON Conditions Front panel Master power button off AC connected. Set formerly OFF (by remote). 1.3 Amps @120Vac
Power ON B
Power ON in remote pressed
1. 2. 3.
2 Relays click immediately Degaussing coil energized (humming sound) TV audio 1 sec after relays click
AC connected. Master power button ON Standby light ON TV OFF 1.3 Amps @120Vac
TV OFF A TV OFF B
Master Power OFF pressed Remote power OFF pressed
2 relays clicks TV sound mutes 2 relays clicks TV sound mutes
When this TV is ON there is no static electricity felt at the CRT screen. It is normal to have black left & right borders on both sides of the picture when viewing a 4:3 aspect ratio picture on a 16x9 aspect ratio TV picture tube.
TV Operation with NO Inputs connected
Selection Video input Access Step Press TV/Video button until video 1, 2, or 3 appear on the screen Press TV/Video button until DVD or HD input is selected. Press the TV button on the remote Press the TV button on the remote Sounds No sound when there is no video input. No sound when there is no input. Off the air white noise from the unconnected VHF/UHF input. Off the air white noise from the unconnected cable input. Visual Video 1, 2, or 3 appears in green letters at the upper left corner of the screen. Screen is dark with no video input. DVD or HD appears in green letters at the upper left corner of the screen. Screen is dark with no input. OSD station number appears in green at the upper right corner of the screen with snow. TV channels can be entered by remote or the up/down buttons will work if stations were programmed during set up. OSD "C _" appears in green at the upper right corner of the screen with snow. Cable channels can be entered by remote or the up/down buttons will work if cable stations were programmed during set up. Conditions Power ON No inputs Power ON No inputs Power ON No inputs Power ON No inputs
DVD, HD, input or High Definition TV input from external box VHF / UHF input
Cable Input
Input Selection
Input VHF / UHF Connections VHF / UHF antenna to rear panel "VHF / UHF" F type connector. 1. 2. 3. Programming Steps Power ON. Use the remote TV/Video button to select TV. The remote ANT button toggles between VHF / UHF and cable. Select VHF / UHF (channel number without a C prefix). rd From the 4 Menu icon, select & enter "Auto Program: VHF / UHF". Use Channel Up/Dwn to change stations for normal operation. Power ON. Use the remote TV/Video button to select TV. The remote ANT button toggles between VHF / UHF and cable. Cable station numbers are preceded with a letter "C". Select a C prefix station like C4. rd From the 4 Menu icon, select & enter "Auto Program: Cable". Use Channel Up/Dwn to change stations for normal operation. Power ON. Use the remote TV/Video button to select TV. The remote ANT button toggles between VHF / UHF and cable. Select VHF / UHF (without a C prefix). rd From the 4 Menu icon, select & enter "Auto Program: VHF / UHF". This tells the set-back box to auto program DTV stations too. ("DTV Auto Add" is only used to add DTV stations after one was found.). Use Channel Up/Dwn to change stations for HDTV reception. Power ON. Use the remote TV/Video button to select the desired input. 1. 2. Results See previous Power ON chart. Snow or a TV station with a channel number will appear if you are correctly in the TV mode. Correct VHF / UHF channels will be numbered 2-69. Cable channels are preceded with a letter C like C78. It takes almost 1 min. to scan through all the VHF / UHF stations. At the end it will select the lowest active VHF station. See previous Power ON chart. Snow or a TV station with a channel number will appear if you are correctly in the TV mode. Correct Cable channels will be displayed as C1 to C125. It takes about 1 min. to scan through all the cable stations. At the end it will select the lowest number active cable station. See previous Power ON chart. Snow or a TV station with a channel number will appear if you are correctly in the TV mode. Correct VHF / UHF channels will be numbered 2-69. Cable channels are preceded with a letter C like C78. It takes about 1 min. to scan through all the VHF/UHF stations. At the end it will select the lowest number active station. See previous Power ON chart. The OSD will show the input selected as you press the TV/Video button. The input sequence is: Video 1-3, DVD, HD, TV and it repeats.
3.
4. 5.
4.
Cable
Connect cable feed to rear panel "Cable" F type connector.
1. 2. 3.
1. 2.
3. 4.
4. 5. High Definition TV Connect an UHF antenna to the DTV Receiver (external set-back box) and the receiver to the rear of the TV using the supplied multi-pin I/O cable. 1. 2. 3. 4.
1. 2.
3.
4.
5. DVD, Video 13, or HD Connect the video and audio cables of the DVD, VCR, game, or camcorder to the rear panel phono jacks. The video 2 input is located on the front panel. The HD box has component video (Y, R-Y, BY) outputs. They plug into the HD input (phono jacks). 1. 2.
1. 2.
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21
Inputs
RF Inputs
There are three independent RF inputs which allow the user to have cable, an outdoor antenna aimed for VHF and UHF stations and another antenna oriented for digital TV stations. Each RF input has a channel numbers assigned to it:
R F C h a n n e l N u m b e r A s s ig n m e n t In p u t C a b le VHF / UHF DTV C h a n n e l N u m b e rs 1 -1 2 5 2 -1 3 / 1 4 -6 9 1 -9 9
This scope shot is taken of a video signal that produces a blue screen. The top waveform is composite video and contains a combined signal. The middle waveform is the chroma signal from the S video output. It contains the burst after the retrace blanking area. The bottom waveform is the luminance signal containing the H sync pulse below the base line.
S Video Input
The S input refers to Separate Video inputs consisting of independent luminance (Y) and chroma (C) signals and a shield wire for each. They are input using a 5 pin standard connector. The fifth pin serves to close a switch in the jack that identifies the presence of the S video plug. The S Video signal is selected instead of the composite video 1-3 when the S video plug is detected. The S video's luminance signal is the picture's brightness level signal. This Y input signal also carries both of the horizontal and vertical sync pulses. The chroma signal contains the color information phase referenced to the burst frequency of 3.58MHz. This C input contains 8 cycles of reference burst signal in the open retrace interval. The chroma signal requires demodulation into individual color components such as RGB before the color information can be used.
They are selected from the ANT remote control button.
Composite Video
This is a single video 1, 2, or 3 input cable that carries the combined Y and C signal. The TV/Video remote control button selects it. This composite signal requires the receiver to first separate the two components, usually using a comb filter. The chroma is demodulated into individual color components, such as RGB, before the color information can be used. These additional processing steps reduce resolution and could add noise, but composite video is a convenient method of transporting a video signal.
PM3394, FLUKE & PHILIPS ch1
Component Video
Conversion
Video can be made of four components: · Luminance or Y which defines the brightness level and · Color, which is made of three components, called R-Y, B-Y and G-Y. We can mathematically calculate the fourth component (G-Y) from the others so only three components are required for video: Assuming R+B+G = Y, and (R-Y)+Y = R, then (G-Y) = -R-B. The manufacture of the G-Y signal can be performed in an electric matrix consisting of summing op amps for adding (+) and subtractive op amps for the difference of the two signals (-). By adding the (inverted) signals, the last G-Y component can be derived.
ch2 1
ch3
2
3
CH1!5.00 V~ CH2!1.00 V~ L=121
CH3! 500mV= CHP MTB10.0us- 1.08dv ch1p
SET-BACK BOX
DIGITAL TV ANTENNA
VHF/UHF (DTV) DOLBY DIGITAL OUTPUT (OPTICAL) DTV I/O FOR USE WITH KW-34HD1 (DTV TV) ONLY
TV TV/VIDEO ANT
- VHF AND SETBACK BOX HDTV
CABLE ANALOG TV INPUT VHF/UHF Y PB
FOR USE WITH HD (1080) INPUT ONLY
HD
RF (ANT) VIDEO 1 VIDEO 2 VIDEO 3 DVD HD
- CABLE
DTV I/O FOR USE WITH KW-34HD1 (DTV RECEIVER) ONLY
MENU
- VIDEO SETTINGS - AUDIO SETTINGS - VERTICAL SIZE AND CENTER - CLOSED CAPTION/VERTICAL SHIFT/TILT
OUT
S VIDEO VIDEO L
(MONO) AUDIO OUT
VAR/FIX
PR L R
DVD
L
(MONO)
1
3
AUDIO R
HD
R
CONTROL S
IN
REAR PANEL KW34HD1 REMOTE CONTROL
INPUTS
HDTV44
22
23
These simple matrixes are found in ICs frequently labeled as decoders or are part of a processor. A video processor IC can contain an additional simple electric matrix to convert the R-Y signals to their base Red signal voltages by just adding the Y signal as (R-Y) + Y = R. The RGB signals output can be used to drive the CRT. R-Y Y resistor A resistor B R signal
3 CH1!5.00 V~ CH2!5.00 V~ L=121 PM3394, FLUKE & PHILIPS ch1
ch2 1
ch3
2
Identification
Component video is usually carried on three lines: Y, R-Y, & B-Y. They can also abbreviated differently, but are the same: · Y, U, V · Y, Cr, Cb · Y, Pr, Pb · Y, R-Y, & B-Y. The Y, Pr, Pb version designates the progressive instead of interlaced picture scan format. This TV selects the DVD or HD component video input from the TV/Video remote button. However, the HD signal must have a horizontal frequency of 31 to 34kHz or the screen will remain dark with just an "HD" OSD.
C hannel 1 C hannel 2 C hannel 3 T im e b a s e
CH3!5.00 V= CHP MTB10.0us- 1.08dv ch1p
B lu e s c r e e n w a v e fo rm Y U V N am e Y B -Y R -Y L o c a t io n D V D o u tp u t D V D o u tp u t D V D o u tp u t 1 0 u s e c / d iv V o lta g e / d iv 7 .5 V p -p 5 V p -p 1 V p -p
Waveforms
The following is a scope shot of component video signals that makes up a blue screen picture. In the top waveform is the Y signal. It houses the horizontal sync pulses (the vertical is not seen at this time base, but it is present in the Y signal). The line between the sync pulses represents the brightness level. The higher the line, the brighter the picture. Therefore, a voltage at the sync pulse level is black. The middle waveform is the B-Y signal. The area corresponding to the horizontal sync pulse in the Y signal is at 0Vdc. The remainder of the voltage minus the Y level is the Blue color level. Since this is a picture of a blue screen, the voltage is high. The bottom waveform is the R-Y signal. The area corresponding to the horizontal sync pulse in the Y signal is also at 0Vdc. The red - Y level during a blue screen is below 0Vdc. It will be equal to 0Vdc if the Y signal is subtracted.
For comparison, the following component video waveforms are of a picture on a blue screen. The Y signal contains voltages of various brightness levels centered on the screen between the H. sync pulses. The B-Y and R-Y signals contain changing color levels in the middle of the screen. Note that by looking at either color signal without the Y signal level, it is not possible to know where the sync area is. It is therefore difficult for your scope to sync on the R-Y or B-Y signal alone without a reference.
PM3394, FLUKE & PHILIPS ch1
ch2
1 ch3
2
3
CH1!10.0 V~ CH2!5.00 V~ L=121
CH3!5.00 V= CHP MTB10.0us- 1.08dv ch1p
P ic tu r e c e n te r e d o n B lu e s c r e e n w a v e f o r m Y s ig N am e C hannel 1 C hannel 2 C hannel 3 T im e b a s e Y B -Y R -Y L o c a t io n D V D o u tp u t D V D o u tp u t D V D o u tp u t 1 0 u s e c /d iv V o lta g e / d iv 7 .5 V p -p 5 V p -p 1 V p -p
SET-BACK BOX
DIGITAL TV ANTENNA
VHF/UHF (DTV) DOLBY DIGITAL OUTPUT (OPTICAL) DTV I/O FOR USE WITH KW-34HD1 (DTV TV) ONLY
TV TV/VIDEO ANT
- VHF AND SETBACK BOX HDTV
CABLE ANALOG TV INPUT VHF/UHF Y PB
FOR USE WITH HD (1080) INPUT ONLY
HD
RF (ANT) VIDEO 1 VIDEO 2 VIDEO 3 DVD HD
- CABLE
DTV I/O FOR USE WITH KW-34HD1 (DTV RECEIVER) ONLY
MENU
- VIDEO SETTINGS - AUDIO SETTINGS - VERTICAL SIZE AND CENTER - CLOSED CAPTION/VERTICAL SHIFT/TILT
OUT
S VIDEO VIDEO L
(MONO) AUDIO OUT
VAR/FIX
PR L R
DVD
L
(MONO)
1
3
AUDIO R
HD
R
CONTROL S
IN
REAR PANEL KW34HD1 REMOTE CONTROL
INPUTS
HDTV44
24
25
Overall Block
There are three main sections in Sony's model KW34HD1 first generation High Definition Television (HDTV): 1. Video Processing 2. Deflection 3. Power Supply The additional circuit blocks in each section and the external box needed to receive the off the air UHF, HDTV signals distinguish this High Definition TV from a conventional TV.
VHF/UHF /Cable Analog Reception
Air or cable selection by the Main Micro is performed at the input antenna switch (SW). Thereafter the signal path is the same. VHF/UHF antenna or cable Input antenna switch (SW) Main/sub tuners Video selector DVD switch DTV switch DRC SEL Video processor RGB Driver CRT cathodes
Video Processing
Because no one HDTV standard has been determined, this first generation HDTV has the flexibility to accept any of the following inputs:
S o n y m o d e l K W 3 4 H D 1 in p u t s In p u t V H F /U H F a n te n n a D ig it a l c h a n n e ls 1 - 9 9 V H F /U H F a n te n n a A n a lo g c h a n n e ls 2 - 6 9 C a b le C h a n n e ls 1 - 1 2 5 V id e o 1 3 P h o n o ja c k s DVD P h o n o ja c k s HD P h o n o ja c k s V id e o P r o c e s s o r D V D S w it c h M a in & S u b T u n e r s v ia a n t e n n a s w it c h M a in & S u b T u n e r s v ia a n t e n n a s w it c h V id e o S e le c t o r S w RF RF C o m p o s it e v id e o ; L & R c h a n n e l a u d io . Y, Pb, Pr L & R c h a n n e l a u d io Y, Pb, Pr L & R c h a n n e l a u d io B lo c k L o c a t io n H D T V e x te rn a l b o x RF S ig n a l f o r m a t
Video Inputs 1 3
Composite video from a VCR or satellite (DSB) receiver Video selector DVD switch DTV switch DRC SEL Video processor RGB Driver CRT cathodes
The signal path for these inputs is shown below:
Digital Input
VHF/UHF antenna HDTV Box (accepts all 18 DTV formats) Video Processor Þ DTV Sw (twin view or SD picture) MID (stores both twin pictures) Sel (selects twin pix path) Video processor Þ RGB Driver Þ CRT
DVD Input
DVD switch DTV switch DRC SEL
ß
RGB Driver CRT cathode
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27
Video processor RGB Driver CRT cathodes Picture tilt and horizontal trapezoid correction Vertical drive (VD) signals not only feed the vertical deflection stage, but also the picture tilt stage that handles trapezoid correction. A controlled level of vertical sawtooth (VD) signal is used for trapezoid correction. This correction signal is mixed with a DC voltage for tilt correction and applied to the N/S coil suspended about the bell of the picture tube by the yoke. Focus There are two focus circuits used in this TV. The dynamic focus circuit uses horizontal pulses to correct the left and right side picture focus caused by the flat screen. The dynamic correction voltage is added into the static (DC) focus voltage that is applied to the picture tube. The quad focus circuit uses both H & V signals to correct spot shape at the four corners of the screen. The circuit's correction voltage is output to four "QP" coils mounted on a board surrounding the picture tube's electron gun.
HD Input
This input is for an external HDTV (perhaps cable) box that receives and decodes the HDTV to output component video: Y, R-Y, B-Y (also called Y, Pb, Pr or Y, Cb, Cr, or Y, U, V, depending upon where you are in the world). The component video path introduces the component video directly into the video processor block. The scan width of this picture is a function of the horizontal frequency. Video processor RGB Driver CRT cathodes
Deflection
The deflection control IC develops signals for:
= = = =
Power Supply
The power supply consists of:
= = = = =
Vertical and horizontal deflection (VD & HD) Horizontal pincushion (EW) Picture tilt & horizontal trapezoid correction (VD) Focus (V blk) Vertical and horizontal deflection The vertical stage is conventional, but the horizontal stage is not. Both the horizontal driver and output stages have individual PWM stages that supply regulated B+ voltage to them. The H. output B+ comes from the PWM stage through the flyback. Horizontal Pincushion The horizontal pincushion correction stage compensates for a picture that is bent inward at the middle of the screen. The E/W correction signal from the deflection controller is amplified and applied to the yoke at the horizontal output transistor's collector to correct for insufficient scan.
A small 60Hz standby power supply that supplies standby +5V to the Main Micro. A Main Micro IC that controls the power relay as well as the deflection, video, and audio stages. A degaussing circuit. Two almost identical converter stages. Converter 2 turns on converter 1. Different voltages are output from each converter to power the TV. A protection circuit to detect excessive voltage and excessive current in various parts of the TV. The protect circuit also monitors vertical drive. A failure in the detected areas causes the power ON command to be removed from AC relay.
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29
Video Block 1
Input Formats
This direct view 34" model KW34HD1 High Definition TV can accept various formats and present them in a single or double Twin View Ò picture. To perform this, each input signal must be processed into a common format, then selected for viewing. The inputs are:
S o n y M o d e l K W 3 4 H D 1 In p u ts In p u t N T S C a n a lo g V H F /U H F c h a n n e ls 2 - 6 9 RF F o rm a t P r o c e s s in g D e m o d u la t io n in t o v id e o . V id e o in t o Y & C . Y & C in t o c o m p o n e n t v id e o ( Y , C b , C r.) C o m p o n e n t v id e o in t o R G B C a b le ( a n a lo g ) c h a n n e ls 1 - 1 2 5 V id e o 1 3 RF C o m p o s it e v id e o L & R a u d io S a m e a s a b o v e e x c e p t d if f e r e n t R F f r e q u e n c ie s a r e r e c e iv e d . V id e o in t o Y & C . Y & C in t o c o m p o n e n t v id e o ( Y , C b , C r.) C o m p o n e n t v id e o in t o R G B C o m p o n e n t v id e o in t o R G B .
The main and sub (Y & C) outputs run parallel paths through similar ICs before leaving the A board. The main and sub signals are converted to component video in Chroma Decoders IC2403 (sub path) and IC2404 (main path). The Y, R-y, B-Y signals are applied to switches IC2405 and IC2406 to enable DVD input selection.
DVD Input
Switches IC2405 and IC2406 can now select between the processed composite video signal and the rear panel DVD input. The DVD signal must also be applied to the sub input line so that it can appear as the second or sub picture in the Twin View mode. Whatever is input on the main picture path is duplicated in the sub path. Switch selection is performed using serial data from the Main Micro IC3251 (not shown). The switched signal is applied to the next switch in both signal paths.
DTV Input
Switches IC2407 and IC2408 introduce the digital TV from the external setback box. This DTV signal path is used when: · Viewing the HD or SD Digital TV signal as a sub picture (Twin View mode); or · The DTV signal is of standard definition (525 lines/480 lines viewable) and line doubling is required. When viewing just the single HDTV picture, the DTV signal is applied directly into the video processor IC3005 (Video Block 3) and does not come this way (except during Twin View).
DVD
C om ponent v id e o L & R a u d io S am e as above
HD
C o m p o n e n t v id e o in t o R G B
Signal Flow
RF Input The RF signals input to the main and sub tuners are channel selected and RF demodulated into composite video. The composite video from the tuner is applied to the video Switch IC2006 along with composite videos 13 from the rear and front panel for user selection.
A Board Output
The main and sub picture paths leave the A board and are passed through the G board into the digital processing stages on the V board. This signal routing through the G board is necessary because both the vertical A and V boards plug into the horizontal G board.
Video Inputs
Video Switch IC2006 selects the video for the main and sub pictures. It also sends the video through comb filters. The comb filters separate the composite video into their luminance (Y) and chroma (C) parts.
Ò Sony, Trinitron, and Twin View are registered trademarks of Sony.
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31
Video Process A
The external video input from the rear panel and internal video from both main and sub tuners is applied to this stage for selection and conversion to (Y, R-y, B-y) component video. The major parts in this early video processing are listed below:
Video Switch
Five composite video inputs are applied to video switch IC2006. Serial data from Main Micro IC3251 (not shown) chooses which input signals take the main and sub picture signal paths. The chosen signals go to their respective comb filters. The 3D filter is always kept in the main picture path and the glass filter (FL2001) is used in the sub picture path. The Y & C outputs from both comb filters are returned to IC2006 and output again. The main picture path is from pins 31 and 35. The sub video path is from switch IC2006/pins 25 and 30 and runs a parallel route to the main one (Video Block 1) for identical processing.
Major Video Processing Components Shown Name Video Switch IC2006 Input 2 tuners, 3 video inputs Y & C from 2 comb filters Buffers Q2016, Q2420, Q2422. YUV Switch ½ IC2406 Buffers Q2015, Q2421 Chroma Decoder IC2404 Output Main Y & C Sub Y & C (similar processing not shown) Purpose Selects composite video Routes to comb filter Y buffers 6db amp C buffers
Component Video
Then the Y signal is input the Chroma Decoder. The chroma (C) signal is also buffered and input to Chroma Decoder IC2404/pin 32. IC2404 uses both the Y & C inputs for level conversion to Y, Cr, Cb (component video).
1Vp-p of Y from 1Vp-p of Y to IC2006/pin 35 IC2406/pin 28 1Vp-p of Y at IC2406/pin 28 1Vp-p of C from IC2006/pin 31 Main Y & C at pins 34 and 32 Y=2Vp-p, C=1Vp-p 2Vp-p at pin 22 1Vp-p of C to IC2404/pin 32 Y = 1Vp-p; Cr, Cb = 0.5Vpp @ pins 18-20
Changes Y/C to component video
All signal levels were taken using a color bar input.
32
33
Video Process B
Signal Flow
Input Selection
Main component video from the Chroma Decoder IC2406 is only one input into switch IC2406. The second input to IC2406 is DVD component video from the rear panel phono jacks. The Main Micro IC3251/pin 78 and 79 sends logic level voltages into IC2406/ pins 25 and 4/27 for the input selection. The chart shows the switching voltages for selecting an input:
I C 2 4 0 6 S e le c tio n I n p u t s e le c te d M a in ( R F , v id e o ) DVD L H I C 2 4 0 6 /p in 2 5 H L I C 2 4 0 6 / p in s 4 , 2 7
DTV Selection
Switch IC2407 chooses between the main and DTV signal for the main picture path. The DTV signal is chosen only when: Viewing the HD or SD Digital TV signal as a sub picture (Twin View mode) or · The DTV signal is of standard definition (525 lines/480 lines viewable) and line doubling is required. The DTV path is chosen when IC2407/pin 9-11 is low: ·
IC 2 4 0 7 S e le c t io n In p u t s e le c t e d M a in ( R F , v id e o ) DTV H L S w s ig n a l IC 2 4 0 7 /p in 9 , 1 0 , 1 1
The output of the DTV/Main switch IC2407 is buffered and sent through the G board to the V board for digital processing.
Closed Caption
The luminance passes through switch IC2406, which adds closed caption or XDS station information as an OSD. If the user requests this feature, this caption information enters IC2406 as an RGB signal from IC2409. The take off or input signal for the closed caption decoder IC2409 is at the output of this YUV switch at IC2406/pin 22.
Filtering
When high frequency analog signals are sent into a digital stage, the high frequency component can create a secondary signal. This second signal is called an alias component. Alias signals are eliminated by low pass filtering (LPF) the analog input. That is the purpose of the filter networks at the output of IC2406.
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35
Video Block 2
Overview
The V board is fully shielded and contains the digital signal processing. The V board is sandwiched in-between the analog A and B boards. All three of these boards plug into the horizontal G board. The V board has the following inputs and outputs:
V B o a r d S ig n a l P r o c e s s in g In p u t ( Y , C r, C b ) M a in S ig n a l C N 5 0 3 / p in s 7 , 9 , 1 1 S u b S ig n a l C N 5 0 3 / p in s 1 , 3 , 5 O u tp u t ( Y , C r, C b ) D R C p ro c e s s e d m a in p ic t u r e o r M ID IC 5 0 6 p r o c e s s e d tw in v ie w p ic tu r e . P u rp o s e S im u la t e s a 9 6 0 - lin e p ic tu r e fr o m a n a c t iv e 4 8 0 lin e N T S C in p u t s ig n a l. S e le c t s o n e (m a in ) o r tw o s im u lt a n e o u s ( T w in V ie w ) p ic tu r e s .
The DRC digital circuitry does more than just double the lines, though that is the primary objective. There are 525 NTSC interlaced lines input (480 viewable lines) to the DRC and 960i (i = interlaced) lines leaving. It is the manner in which the extra lines are created that makes the DRC circuit unique. DRC and MID concept explanations are in the pages that follow. The main picture signal is input to the MID IC directly. The sub picture signal is converted to a digital signal by A/D Converter IC607 before becoming the other input for the MID IC. The MID digital circuitry reduces this sub and the main picture to fit on the screen at the same time. This coexistence feature is called Twin View. The analog output of the MID IC is low pass filtered by filter 1 to reduce D/ A converter noise. Filter 2 is selected in the Japanese version of this TV set when there is a computer signal input to that version. In the USA TV, IC519 is never toggled from the position shown. Either the main or the Twin View picture is selected by IC528 and this resultant signal is sent to the next (B) board.
Signal Flow
The main picture signal is applied to both the DRC and MID digital circuitry for processing:
D ig ita l C ir c u itr y N am e D R C D ig ita l R e a lit y C r e a t io n P u rp o s e D o u b le s s c a n n in g lin e s a n d p ix e ls a ft e r m a s s iv e p r e s e n t a n d p r e v io u s lin e in f o r m a tio n a n a ly s is . A c c e p ts b o th 4 8 0 - o r /a n d 9 6 0 - lin e c o m p o n e n t v id e o im a g e s ( m a in / s u b ) a n d c o n v e rts th e m in to a t w in p ic tu r e .
M I D M u lti I m a g e D r iv e r
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DRC - Digital Reality Creation
Another picture quality issue has been with us since the dawn of television. Deeply ingrained in our television system is the question of visible scanning lines. All about scanning lines A television picture is "painted" across the CRT screen by an electron beam that scans on a horizontal line from left to right. Once the beam reaches the ridge edge, it shuts off and returns to the left edge to start another line. All told, there are some 525 scanning lines in the American NTSC (National Television Standards Committee) television system, and they create a new television picture or "frame" some 30 times a second. Over the years, the 480i system has worked remarkably well. But with only 240 lines on-screen at any one time, the scanning lines can become painfully obvious, particularly when you're sitting close to a large-screen display. Problem: Visual scanning lines Originally, television engineers designed the NTSC system so that the picture would appear seamless when viewed from a distance of 8 times the picture height. This worked well in an era when the biggest commercially available screens were 12 inches diagonal. But in today's big-screen era, viewers tend to set far closer to their televisions in order to get wrapped up in the action. Under these conditions, the scanning lines become blatantly visible. One solution: Line doublers Demanding home theater enthusiasts, videophiles and video professionals have long sought a cure for this problem. One solution is to double the number of scanning lines with a circuit called a line doubler. Sony has been an active supplier of line doublers, particularly for professional video projectors.
In reality, you don't see the full 525 lines on the screen. Over 40 lines are consumed by the Vertical Blanking interval. This leaves roughly 480 lines for the actual picture. And you don't even see the 480 lines all at once. Each video frame is divided into two "fields", which last for 1/60th of a second. The first field is composed of all the odd-numbered lines (1, 3, 5 and so on). The second field "fills in" with the even-numbered lines. This technique of alternating odd and even fields is called "interlacing." The NTSC system is often referred to as "525/60" (for 525 total scanning lines and 60 fields per second). It is also called "480I" (for 480 net scanning lines, interlaced).
Many line doublers attempt to de-interlace the 480i NTSC signal, displaying both fields simultaneously in a 480-line "progressive" scan. Progressive scanning combines the separate fields of odd-numbered lines and even-numbered lines. Progressive scanning displays every line in a frame in numeric sequence line 1, 2, 3, 4 and so on up to line 480. Progressive scan plays a central role in computer displays where it helps to make text more legible. Line doublers turn interlaced 480i signals into a progressive 480P. This concept works perfectly for still images, because the two fields match up completely. But on moving images, the even field is captured 1/60th second later than the odd field. So a car traveling on the screen has driven 1/60th second further down the street. And a baseball player has slid 1/60th second closer to home plate. For this reason, line-doublers require elaborate motion-detection, motion-compensation and memory circuits. This can get expensive, with the better line doublers costing $2,500 or more.
A new solution: DRC Sony's new Digital Reality Creation (DRC) circuitry is an all-new approach to the problem of visible scanning lines. Not only does DRC create a clearer picture by doubling the number of active scanning lines it also doubles the number of pixels on each scanning line. You get four times the picture density of standard 480i, making this a significant step toward the picture quality of true High Definition TV (HDTV).
How it works The new DRC circuit is based upon a massive analysis of over tens of thousands of High Definition TV picture patterns. Because there is a fixed relationship between NTSC patterns and their HDTV equivalents, Sony's exclusive microprocessor can simply replace the NTSC signal with its correct DRC counterpart. In operation, the DRC circuit accepts a digitally sampled 13.5 M H z input and generates a quadrupled 54.0 MHz digital output.
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Moreover, with DRC, each field is processed separately, so there's never a need to compensate for motion between two fields. And while the doublers typically produce a scan of 480P, the DRC circuit produces a higher line rate, 960i, for even greater image density. What it all means Digital Reality Creation circuitry greatly enhances the television viewing experience. Now you can sit up close to the screen, immersing yourself in the magic of home entertainment and still not be bothered by visible scanning lines. Pictures appear denser and more seamless. And in the coming world of Digital TV (DTV) broadcasting, televisions with Digital Realty Creation circuitry will narrow the perceived gap among NTSC analog sources, standard definition digital and full High Definition digital video.
Line doubling improves vertical density
DRC doubles both vertical and horizontal density
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MID - Multi Image Driver
The world of NTSC has been a simple world. The 480i video cameras give their signals to 480i video recorders, 480i producti