IPP Codecs

Implementation of IPP codecs. More...

Functions
pj_status_t	pjmedia_codec_ipp_init (pjmedia_endpt *endpt)
pj_status_t	pjmedia_codec_ipp_deinit (void)

Detailed Description

This section describes functions to initialize and register IPP codec factory to the codec manager. After the codec factory has been registered, application can use Codec Framework API to manipulate the codec.

This codec factory contains various codecs, i.e: G.729, G.723.1, G.726, G.728, G.722.1, AMR, and AMR-WB.

IPP G.729

IPP G.729 is compliant with ITU-T G.729 and Annexes A, B, C, C+, D, E, I specifications. However, currently the pjmedia implementation is using Annexes A and B only.

IPP G.729 supports 16-bit PCM audio signal with sampling rate 8000Hz, frame length 10ms, and resulting in bitrate 8000bps (annexes D and E introduce bitrates 6400bps and 11800bps).

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

Note that G.729 VAD status should be signalled in SDP, see more description below.

Annex B

The capability of VAD/DTX is specified in Annex B.

By default, Annex B is enabled. This default setting of Annex B can be modified using pjmedia_codec_mgr_set_default_param().

In pjmedia_codec_param, Annex B is configured via VAD setting and format parameter "annexb" in the SDP "a=fmtp" attribute in decoding fmtp field. Valid values are "yes" and "no", the implementation default is "yes". When this parameter is omitted in the SDP, the value will be "yes" (RFC 4856 Section 2.1.9).

Here is an example of modifying default setting of Annex B to be disabled using pjmedia_codec_mgr_set_default_param():

pjmedia_codec_param param;
 
pjmedia_codec_mgr_get_default_param(.., &param);
...
// Set VAD
param.setting.vad = 0;
// Set SDP format parameter
param.setting.dec_fmtp.cnt = 1;
param.setting.dec_fmtp.param[0].name = pj_str("annexb");
param.setting.dec_fmtp.param[0].val  = pj_str("no");
...
pjmedia_codec_mgr_set_default_param(.., &param);

Note

The difference of Annex B status in SDP offer/answer may be considered as incompatible codec in SDP negotiation.

IPP G.723.1

IPP G.723.1 speech codec is compliant with ITU-T G.723.1 and Annex A specifications.

IPP G.723.1 supports 16-bit PCM audio signal with sampling rate 8000Hz, frame length 30ms, and resulting in bitrates 5300bps and 6300bps.

By default, pjmedia implementation uses encoding bitrate of 6300bps. The bitrate is signalled in-band in G.723.1 frames and interoperable.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

IPP G.726

IPP G.726 is compliant with ITU-T G.726 and G.726 Annex A specifications.

IPP G.726 supports 16-bit PCM audio signal with sampling rate 8000Hz, 10ms frame length and producing 16kbps, 24kbps, 32kbps, 48kbps bitrates. The bitrate is specified explicitly in its encoding name, i.e: G726-16, G726-24, G726-32, G726-48.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

IPP G.728

IPP G.728 is compliant with ITU-T G.728 with I, G, H Appendixes specifications for Low-Delay CELP coder.

IPP G.728 supports 16-bit PCM audio signal with sampling rate 8000Hz, 20ms frame length and producing 9.6kbps, 12.8kbps, and 16kbps bitrates.

The pjmedia implementation currently uses 16kbps bitrate only.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

IPP G.722.1

The pjmedia implementation of IPP G.722.1 supports 16-bit PCM audio signal with sampling rate 16000Hz, 20ms frame length and producing 16kbps, 24kbps, and 32kbps bitrates.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

Bitrate

The codec implementation supports only standard bitrates, i.e: 24kbps and 32kbps. Both are enabled by default.

Remarks

There is a flaw in the codec manager as currently it could not differentiate G.722.1 codecs by bitrates, hence invoking pjmedia_codec_mgr_set_default_param() may only affect a G.722.1 codec with the highest priority (or first index found in codec enumeration when they have same priority) and invoking pjmedia_codec_mgr_set_codec_priority() will set priority of all G.722.1 codecs with sampling rate as specified.

IPP AMR

The IPP AMR is compliant with GSM06.90-94 specifications for GSM Adaptive Multi-Rate codec.

IPP AMR supports 16-bit PCM audio signal with sampling rate 8000Hz, 20ms frame length and producing various bitrates that ranges from 4.75kbps to 12.2kbps.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

Bitrate

By default, encoding bitrate is 7400bps. This default setting can be modified using pjmedia_codec_mgr_set_default_param() by specifying prefered AMR bitrate in field info::avg_bps of pjmedia_codec_param. Valid bitrates could be seen in pjmedia_codec_amrnb_bitrates.

Payload Format

There are two AMR payload format types, bandwidth-efficient and octet-aligned. Default setting is using octet-aligned. This default payload format can be modified using pjmedia_codec_mgr_set_default_param().

In pjmedia_codec_param, payload format can be set by specifying SDP format parameters "octet-align" in the SDP "a=fmtp" attribute for decoding direction. Valid values are "0" (for bandwidth efficient mode) and "1" (for octet-aligned mode).

Mode-Set

Mode-set is used for restricting AMR modes in decoding direction.

By default, no mode-set restriction applied. This default setting can be be modified using pjmedia_codec_mgr_set_default_param().

In pjmedia_codec_param, mode-set could be specified via format parameters "mode-set" in the SDP "a=fmtp" attribute for decoding direction. Valid value is a comma separated list of modes from the set 0 - 7, e.g: "4,5,6,7". When this parameter is omitted, no mode-set restrictions applied.

Here is an example of modifying AMR default codec param:

pjmedia_codec_param param;
 
pjmedia_codec_mgr_get_default_param(.., &param);
...
// set default encoding bitrate to the highest 12.2kbps
param.info.avg_bps = 12200;
 
// restrict decoding bitrate to 10.2kbps and 12.2kbps only
param.setting.dec_fmtp.param[0].name = pj_str("mode-set");
param.setting.dec_fmtp.param[0].val  = pj_str("6,7");
 
// also set to use bandwidth-efficient payload format
param.setting.dec_fmtp.param[1].name = pj_str("octet-align");
param.setting.dec_fmtp.param[1].val  = pj_str("0");
 
param.setting.dec_fmtp.cnt = 2;
...
pjmedia_codec_mgr_set_default_param(.., &param);

IPP AMR-WB

The IPP AMR-WB is compliant with 3GPP TS 26.190-192, 194, 201 specifications for Adaptive Multi-Rate WideBand codec.

IPP AMR-WB supports 16-bit PCM audio signal with sampling rate 16000Hz, 20ms frame length and producing various bitrates. Valid bitrates could be seen in pjmedia_codec_amrwb_bitrates. The pjmedia implementation default bitrate is 15850bps.

Codec Settings

General codec settings for this codec such as VAD and PLC can be manipulated through the setting field in pjmedia_codec_param. Please see the documentation of pjmedia_codec_param for more info.

Bitrate

By default, encoding bitrate is 15850bps. This default setting can be modified using pjmedia_codec_mgr_set_default_param() by specifying prefered AMR bitrate in field info::avg_bps of pjmedia_codec_param.

Payload Format

There are two AMR payload format types, bandwidth-efficient and octet-aligned. Default setting is using octet-aligned. This default payload format can be modified using pjmedia_codec_mgr_set_default_param().

In pjmedia_codec_param, payload format can be set by specifying SDP format parameters "octet-align" in the SDP "a=fmtp" attribute for decoding direction. Valid values are "0" (for bandwidth efficient mode) and "1" (for octet-aligned mode).

Mode-Set

Mode-set is used for restricting AMR modes in decoding direction.

By default, no mode-set restriction applied. This default setting can be be modified using pjmedia_codec_mgr_set_default_param().

In pjmedia_codec_param, mode-set could be specified via format parameters "mode-set" in the SDP "a=fmtp" attribute for decoding direction. Valid value is a comma separated list of modes from the set 0 - 7, e.g: "4,5,6,7". When this parameter is omitted, no mode-set restrictions applied.

Function Documentation

pjmedia_codec_ipp_init()

pj_status_t pjmedia_codec_ipp_init

(

pjmedia_endpt *

endpt

)

Initialize and register IPP codecs factory to pjmedia endpoint.

Parameters

endpt

The pjmedia endpoint.

Returns

PJ_SUCCESS on success.

pjmedia_codec_ipp_deinit()

pj_status_t pjmedia_codec_ipp_deinit

(

void

)

Unregister IPP codecs factory from pjmedia endpoint and deinitialize the IPP codecs library.

Returns

PJ_SUCCESS on success.

References PJ_END_DECL.