GV7704 Datasheet, PDF (20/52 Pages) Semtech Corporation – Quad HD-VLC Receiver

4.4.2 HD-VLC Decoding
The GV7704 integrates the High Definition Visually Lossless CODEC (HD-VLC) decoder
for extended reach video reception. When used in conjunction with the GV7700 HD-VLC
transmitter, HD video transmission can be extended significantly over existing HD serial
digital video systems. HD-VLC is based on a simple visually lossless implementation of
the Dirac compression tool kit (http://diracvideo.org/) The visually lossless decoder is
used to reduce the video bandwidth, using a very low latency mode, from a
transmission rate of 1.485Gb/s (HD-SDI) to 270Mb/s (SD-SDI).
At a data rate of 270Mb/s, the serial digital encoded HD video can be transmitted over
longer runs of coaxial cable. Table 4-2 below shows a comparison of cable distances
between HD video transmission at 1.485Gb/s and HD-VLC encoded at 270Mb/s for
various common coaxial cable types.
Table 4-2: Cable Reach for Various Cable Types (In Metres)
Cable Type
HD-VLC: 270Mb/s (m) HD-SDI: 1.485Gb/s (m)
Belden 1694A / Canare L-4.5CHD
710
230
Belden 543945
550
150
KW-Link SYV 75-5
500
140
Canare L-3C2V
300
95
KW-Link SYV 75-3
300
85
Note: These values apply for new, properly terminated cables. Actual performance may vary.
Note: The serial data output should be disabled to achieve maximum SDI cable reach.
After transmission over the coaxial cable, the 270Mb/s serial data is recovered using the
GV7704 and the data is decoded back into the native HD format. The encoding and
decoding process has a total latency of 12-14 HD lines, which makes the CODEC ideal for
low latency real-time applications. Table 4-3 below shows the total encode/decode
latency through the GV7704 and the GV7700.
Table 4-3: Encode and Decode Total Latency (GV7704 + GV7700)
Video Format
1080p25
1080p29.97
1080p30
720p25
720p29.97
720p30
720p50
720p59.94
720p60
Delay (μs)
422.2
368.8
368.4
635.1
546.6
546.6
368.6
324.2
324.2
Delay (HD Lines)
11.9
12.4
12.4
11.9
12.2
12.2
13.8
14.5
14.5
GV7704
Preliminary Data Sheet Rev.3
PDS-060376
September 2015
www.semtech.com
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Semtech