GS2971A Datasheet, PDF (85/152 Pages) Gennum Corporation – Integrated audio clock generator

In 3G Level A signals, the audio data packets must be embedded only in Data Stream
Two.
In 3G Level B signals, the audio data packets must be embedded in the Chroma streams
of either Link A or Link B.
The Audio Group Detect registers are set HIGH when audio data packets with a
corresponding group DID are detected in the input video stream. The host interface
reports the individual audio groups detected.
Table 4-18:Audio Data Packet Detect Register
Name
ADPG4_DET
ADPG3_DET
ADPG2_DET
ADPG1_DET
Description
Audio Group Four Data Packet Detection (1: Detected)
Audio Group Three Data Packet Detection (1: Detected)
Audio Group Two Data Packet Detection (1: Detected)
Audio Group One Data Packet Detection (1: Detected)
Default
0
0
0
0
When an audio data packet with a DID set in IDA[1:0] and IDB[1:0] is detected, the audio
sample information is extracted and written into the audio FIFO.
The embedded audio group selected by IDA[1:0] is described henceforth in this
document as Group A or Primary Group. The embedded audio group selected by
IDB[1:0] is described henceforth in this document as Group B or Secondary Group.
Due to the large size of the horizontal ancillary data space in 720p/24, 720p/25 and
720p/30 video standards, the maximum number of ancillary data words the audio
de-embedder can process is limited to 1024 when configured for these standards.
4.19.2.3 Audio Control Packets
The audio de-embedder automatically detects the presence of audio control packets in
the video stream. When audio control packets for audio Group A are detected, the
CTRA_DET bit of the host interface is set HIGH. When audio control packets for audio
Group B are detected, the CTRB_DET bit of the host interface is set HIGH.
The audio control packet data is accessible via the host interface.
The audio control packets must be embedded according to SMPTE 272M (SD) or SMPTE
299M (HD and 3G). In 3G Level A signals, the audio control packets must be embedded
only in Data Stream One. In 3G Level B signals the audio control packets must be
embedded in the Luma streams of each link that carries audio.
NOTE 1: In SD, the control packet host interface registers are updated with new control
packet values, after the CTRA_DET/CTRB_DET flags are cleared. In HD, the update
happens automatically.
NOTE 2: If there is an HD audio packet checksum error, no audio is extracted. The audio
packet is not recognized and the audio stays in the video stream. If nothing but the CLK
phase parity bit is wrong, the audio will extract fine.
GS2971A 3Gb/s, HD, SD SDI Receiver
Data Sheet
54311 - 2
September 2012
85 of 152