GS2972 Datasheet, PDF (51/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.7.7 Audio Packet Detection
The input video stream to the GS2972 may already contain embedded audio packets.
The GS2972 detects these embedded packets, and signals their presence to the host
interface. Register 404h is used for SD, register 803h is used for HD/3G.
4.7.8 Audio Packet Deletion
In Normal Mode (default), the GS2972 deletes all audio packets from the input video
data stream.
In Cascade Mode, the GS2972 does not delete any audio packets from the input video
data stream.
In Group Replacement Mode, the GS2972 does not delete any audio packets from the
input video data stream.
In all operating modes, the GS2972 deletes all audio packets from the input video stream
if any embedded audio packets do not fully comply with the SMPTE ST 291 standard.
4.7.9 Audio Packet Detection and Deletion
In SD modes, the first Ancillary Data Flag (ADF) must always be contiguous after the
EAV words. For HD mode, the first ADF must always be contiguous after the two line
CRC words.
Ancillary data packets with non-audio data ID words, such as arbitrary, EDH (SD only),
SDTI header and SMPTE ST 352, are not deleted from the data stream. On lines where
SMPTE ST 352 or SDTI header packets exist, the audio data packets must be contiguous
from the ST 352 and SDTI packets. If this is not the case, all existing audio data and
control packets will be deleted.
When CASCADE is set HIGH, all pre-existing audio data and control packets remain in
the video stream.
When the AGR bit in the host interface is set HIGH, Audio Group Replacement mode is
selected. In this mode, existing audio data and control packets are not deleted from the
data stream.
In cases where the ADF is not placed immediately after the CRC or EAV words, or there
are gaps between the packets, the audio core deletes all existing audio data and control
packets, regardless of the CASCADE or AGR setting. Figure 4-27 shows an example of
correct and incorrect placement of ancillary data packets for SD Mode.
GS2972 3G/HD/SD-SDI Serializer with Complete
SMPTE Audio & Video Support
Final Data Sheet Rev. 9
GENDOC-047479 September 2013
www.semtech.com
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