GV7704 Datasheet, PDF (27/52 Pages) Semtech Corporation – Quad HD-VLC Receiver

The GV7704 looks for packets in the horizontal blanking region of a digital video signal.
The vertical blanking region is used by the HD-VLC encoder of the GV7000 which inserts
compression coefficients that cannot be overwritten. The payload of the ancillary data
packet can be used to carry user-defined or proprietary data, which can be sent between
an Aviia transmitter and receiver.
The ancillary data packet is formatted according to the Figure 4-10 below. The packet
must always begin with the Ancillary Data Flag (ADF), defined as the following 10-bit
word sequence: 000_h, 3FF_h, 3FF_h.
The next data word is the 8-bit Data ID (DID), used to define the contents of the packet.
For example, a unique DID can be used to denote alarm data, with another DID to
denote status data.
After the DID, there are two possible options, as shown in Figure 4-10.
Type 1 Ancillary Data Packet
MSB
Not b8
Parity bit
LSB
Type 2 Ancillary Data Packet
MSB
User Data Words
Not b8
Parity bit
LSB
User Data Words
Figure 4-10: Ancillary Data Packets
A Type 1 packet defines an 8-bit Data Block Number (DBN) sequence, used to
distinguish successive packets with the same DID. The DBN simply increments with each
packet of the same DID, between 0 and 15.
For a Type 2 packet, an 8-bit Secondary Data ID (SDID) word is defined, which can be
used to denote variants of payloads with the same DID. For example, packets with a DID
to denote error data may distinguish different error types using unique SDID's.
After the DBN or SDID, the next data word is the 8-bit Data Count (DC). This word must
be set to the number of user data words (UDW) that follow the DC, and must not exceed
16 (maximum payload size).
The final word of the ancillary data packet is the 9-bit Checksum (CS). The CS value must
be equal to the nine least significant bits of the sum of the nine least significant bits of
the DID, the DBN or the SDID, the DC and all user data words (UDW) in the packet.
For HD video formats, ancillary data packets are only extracted from the Luma channel.
GV7704
Preliminary Data Sheet Rev.3
PDS-060376
September 2015
www.semtech.com
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Semtech