GS2972 Datasheet, PDF (50/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.7.5 SD Mode
When the GS2972 is operating in SD mode, eight channels of audio in four pairs are
embedded in the serial output signal, according to SMPTE ST 272. The eight channels
will be in two groups, which are selectable via the host interface from the four groups
allowed by SMPTE ST 272. The default group is Group One and Group Two.
4.7.6 Audio Embedding Operating Modes
Audio Embedding operates in one of three distinct modes:
1. Normal Mode (Default)
All previously embedded audio packets are deleted from the video stream.
Arbitrary packets, SDTI packets and SMPTE ST 352 packets are not deleted.
Up to two audio groups can be added to the video output.
SDTI packets and SMPTE ST 352 packets are placed before the audio packets.
Arbitrary packets are placed after the audio packets.
2. Cascade Mode
No previously embedded packets are deleted from the video stream.
Up to two audio groups can be added to the video output.
The added audio groups will not replace existing embedded audio groups.
The added audio packets are appended to the last packet in the video input.
3. Group Replacement Mode
All packets associated with the groups being replaced are deleted.
Up to two audio groups can be added to the video output.
The added audio groups replace any embedded audio groups with the same group
number. This will not affect any of the other audio groups, and they will remain in the
data stream.
The embedded audio groups are sorted in ascending order by audio group number.
SDTI packets and SMPTE ST 352 packets are placed before the audio packets.
Arbitrary packets are placed after the audio packets.
The operating mode is selected using a combination of the EN_CASCADE and the AGR
bits in the host interface, as stated in Table 4-8 below.
Table 4-8: GS2972 Audio Operating Mode Selection
Control Signals
EN_CASCADE=0, AGR=0
EN_CASCADE=1, AGR=0
EN_CASCADE=0, AGR=1
EN_CASCADE=1, AGR=1
Operating Mode
Normal Mode
Cascade Mode
Group Replacement Mode
Group Replacement 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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