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32 Dialogic
®
Multimedia Software for ATCA Release 1.0 Release Update, Rev 06 — January 23, 2008
Dialogic Corporation
ipmMediaInfo.MediaData[unCount].eMediaType = MEDIATYPE_AUDIO_REMOTE_CODER_OPTIONS_INFO;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.unVersion =
IPM_AUDIO_CODER_OPTIONS_INFO_VERSION;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.unCoderOptions =
CODER_OPT_SIGNALING_OFF;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.unParm1 =
CODER_OPT_INTERLEAVE_LENGTH;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.nValue1 = 6;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.unParm2 = 0;
ipmMediaInfo.MediaData[unCount].mediaInfo.AudioCoderOptionsInfo.nValue2 = 0;
unCount++;
ipmMediaInfo.unCount = unCount;
3.3.9 Dialogic
®
IP Media Library API Programming Guide
Using AMR coders for narrow band audio and using enhanced variable rate codecs
The following information, which is applicable to the ATCA Multimedia Platform,
should be added to the programming guide, possibly as a new chapter.
Using AMR Coders for Narrow Band Audio
Description
AMR is an adaptive multi-rate speech codec. During operation, both local and remote sides can
request a change in the bit rate and dynamically adjust the bandwidth. The protocol uses the
following:
• A Frame Type (FT) to indicate the transmitted bit rate
• A Codec Mode Request (CMR) value to request a particular bit rate in every packet
To control the bit rate, AMR assumes that all connections are bi-directional.
This feature is specific to AMR-NB and excludes support for AMR-WB and AMR-WB+, which
support wideband audio and some other formats not addressed by AMR.
The codec supports the following bit rates:
• 12.2 kbit/s (GSM EFR)
• 10.2 kbit/s
• 7.95 kbit/s
• 7.40 kbit/s (IS-641)
• 6.70 kbit/s (PDC-EFR)
• 5.90 kbit/s
• 5.15 kbit/s
• 4.75 kbit/s
• 1.80 kbit/s (assuming SID frames are continuously transmitted)
Note: The 1.80 kbit/s rate is not actually a voice signal, but the bit rate consumed when Voice Activation
Detection (VAD) is processing a silence.