HD-SDI Input
Audio can be embedded on a serial digital interface (
HD-SDI
) feed within four groups. Each group contains two pairs. Hence each
HD-SDI 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.
SD-SDI Input
Audio can be embedded on a serial digital interface (
SDI
) feed within four groups. Each group contains two pairs. Hence each SDI
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.
Audio Input
The
digital
input of the VCM accepts four stereo pairs of digital audio.
See
Technical Specification
for more details.
CAUTION...
When the digital audio source is used with the AUDIO IN connector, consideration must be given to the choice of clock source used
by the Encoder. To ensure correct operation, both the Encoder and the audio source may need to be genlocked to the studio source
by selecting the video clock as external. Then the encoding clock is derived from an
External Sync
module.
Audio Encoding Modes
Up to eight audio channel pairs of uncompressed audio can be encoded in accordance with MPEG-1 Layer II, subject to license key
SWO/M1L2 for more than two channel pairs.
If a SWO/AC3 license key is available, two audio channel pairs may be encoded in accordance with the Dolby Digital specification.
Pre-encoded Dolby Digital, Dolby Digital Plus and Dolby E inputs can be suitably encapsulated for inclusion in an output transport
stream.
The VCM can generate a 1 kHz test tone, which may be used in place of any audio input.
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 synchronisation (lipsync) is maintained.
All Audio modes are configurable on a per channel basis, which includes the source of the audio, its encoding configuration and
output PID.
The following is a summary of the Audio Compression functionality available.
Function
Comments
Maximum number of instances
MPEG-1 Layer II audio
The encode of two channel pairs is provided as
standard. More than two encodes require
the /SWO/M1L2 license (one license for each
additional channel pair)
8 (mono or stereo)
Dolby Digital encoding
Only available if /SWO/DOLBY/AC3 license has
2 (mono or stereo)
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