6.4 VCM Audio Functionality
The VCMs support a wide variety of input audio signals, and can encode them in
various formats or pass them as they are received (Pass-thru mode).
Any audio input can be associated with the video being processed, and the audio
encoding delay will be matched to the video encoding delay so that audio/video
synchronization (lipsync) is maintained.
All audio components are configurable on a per channel basis. Parameters include
the source of the audio, its encoding configuration and output PID.
6.4.1 HD-SDI Input
The VCM can receive four groups of audio streams embedded in the HD serial
digital interface (HD-SDI) feed. Each group contains two channel pairs. Hence the
HD-SDI feed can carry up to a maximum of 2 x 4 = 8 pairs, or 16 mono channels.
Each group has an associated Data Identifier (DID). The DIDs are set to the
SMPTE 299M defaults for audio group 1 to group 4:
• Group 1 = 0x2E7
• Group 2 = 0x1E6
• Group 3 = 0x1E5
• Group 4 = 0x2E4
The DIDs are located in ancillary packets in the data stream. They are fixed at the
SMPTE 299M defaults.
6.4.2 SDI Input
The VCM can receive four groups of audio streams embedded in the serial digital
interface (SDI) feed. Each group contains two channel pairs. Hence the SDI feed
can carry up to a maximum of 2 x 4 = 8 pairs, or 16 mono channels.
Each group has an associated Data Identifier (DID). The DIDs are set to the
SMPTE 272M defaults for audio group 1 to group 4:
• Group 1 = 0x2FF
• Group 2 = 0x1FD
• Group 3 = 0x1FB
• Group 4 = 0x2F9
The DIDs are located in ancillary packets in the data stream. They are fixed at the
SMPTE 272M defaults. DID 1F4 is reserved for EDH error packets. Refer to the
SMPTE 272M specification for more details.
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