Technical Specification
Linear PCM
For passing through 2 channels (1 channel pair) of uncompressed data the audio
module complies with SMPTE 302M standard. The module supports 24, 20 and 16
bit word sizes on the input and output. The bit-depth option defines the output word
size and is independent of the input. Only 2 channels are supported per PID.
Dolby E
The audio module can Pass-thru pre-encoded Dolby E audio. The input word size is
automatically detected, and this is applied to the output. Only 1 Dolby E stream is
supported per PID. Complies with SMPTE 302M, SMPTE 337M and SMPTE 338M.
• SMPTE 302M: Mapping of AES3 Data into MPEG-2 Transport Stream.
• SMPTE 337M: Format for Non-PCM Audio and Data in AES3 Serial Digital
Audio Interface.
• SMPTE 338M: Format for Non-PCM Audio and Data in AES3 - Data Types.
B.3.12.6 Audio Test Tone
The module is able to generate a test tone on any audio channel at 1 kHz, with a
level of -18 dBFS.
Note If there is no source connected to the SDI input then Input Detection must
be set to Off otherwise the resulting test tone can “warble”.
B.3.12.7 Maximum Audio Encode Capability
It is possible to configure any combination of audio coding modes within the
constraints of available processing power for each audio module. Each audio coding
mode requires a definitive amount of CPU resource so is allocated an associated
points weighting. The sum of the weighting for the configured audio encodes cannot
exceed 100 for each audio module. There are 2 audio modules available on the
VCM. The first takes audio 1 to 8 and the second takes audio 9 to 16. A single audio
coding instance cannot use resources from both modules. If a warning informs you
that there is insufficient resource available, the configuration needs to be changed
so that the other module is used.
The following is a summary weighting points for each Audio Encoding mode.
Table B.25 Weighting Points for Audio Encoding Modes
Function Available Coding Modes Weighting (points)
MPEG-1 Layer II audio encoding Mono 1.0 (center, from left)
Mono 1.0 (center, from right)
1+1 Dual Mono
Stereo (2.0)
Joint Stereo (2.0)
10
Phase Aligned MPEG-1 Layer II
audio encoding
6 Channel Aligned 30
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