diff options
Diffstat (limited to 'pjmedia/include/pjmedia-codec/passthrough.h')
| -rw-r--r-- | pjmedia/include/pjmedia-codec/passthrough.h | 183 |
1 files changed, 177 insertions, 6 deletions
diff --git a/pjmedia/include/pjmedia-codec/passthrough.h b/pjmedia/include/pjmedia-codec/passthrough.h index 7a47af1a..828f5d65 100644 --- a/pjmedia/include/pjmedia-codec/passthrough.h +++ b/pjmedia/include/pjmedia-codec/passthrough.h @@ -33,17 +33,188 @@ * @brief Implementation of passthrough codecs * @{ * - * This section describes functions to register and register passthrough + * This section describes functions to initialize and register passthrough * codecs factory to the codec manager. After the codec factory has been * registered, application can use @ref PJMEDIA_CODEC API to manipulate - * the codec. This codec factory contains various codecs, e.g: G.729, iLBC, - * AMR, and G.711. + * the codec. * - * Passthrough codecs are codecs wrapper that does not perform encoding - * or decoding, it just pack and parse encoded audio data from/into RTP + * Passthrough codecs are codecs wrapper that does NOT perform encoding + * or decoding, it just PACK and PARSE encoded audio data from/into RTP * payload. This will accomodate pjmedia ports which work with encoded * audio data, e.g: encoded audio files, sound device with capability * of playing/recording encoded audio data. + * + * This codec factory contains various codecs, i.e: G.729, iLBC, + * AMR, and G.711. + * + * + * \section pjmedia_codec_passthrough_g729 Passthrough G.729 + * + * G.729 supports 16-bit PCM audio signal with sampling rate 8000Hz, + * frame length 10ms, and resulting in bitrate 8000bps. + * + * \subsection codec_setting Codec Settings + * + * General codec settings for this codec such as VAD and PLC can be + * manipulated through the <tt>setting</tt> 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. + * + * \subsubsection annexb 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(): + \code + pjmedia_codec_param param; + + pjmedia_codec_mgr_get_default_param(.., ¶m); + ... + // 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(.., ¶m); + \endcode + * + * \note + * The difference of Annex B status in SDP offer/answer may be considered as + * incompatible codec in SDP negotiation. + * + * + * \section pjmedia_codec_passthrough_ilbc Passthrough iLBC + * + * The iLBC codec is developed by Global IP Solutions (GIPS), formerly + * Global IP Sound. The iLBC offers low bitrate and graceful audio quality + * degradation on frame losses. + * + * The iLBC codec supports 16-bit PCM audio signal with sampling rate of + * 8000Hz operating at two modes: 20ms and 30ms frame length modes, resulting + * in bitrates of 15.2kbps for 20ms mode and 13.33kbps for 30ms mode. + * + * \subsection codec_setting Codec Settings + * + * General codec settings for this codec such as VAD and PLC can be + * manipulated through the <tt>setting</tt> field in #pjmedia_codec_param. + * Please see the documentation of #pjmedia_codec_param for more info. + * + * \subsubsection mode Mode + * + * The default mode should be set upon initialization, see + * #pjmedia_codec_passthrough_init2(). After the codec is initialized, the + * default mode can be modified using #pjmedia_codec_mgr_set_default_param(). + * + * In #pjmedia_codec_param, iLBC mode can be set by specifying SDP + * format parameter "mode" in the SDP "a=fmtp" attribute for decoding + * direction. Valid values are "20" and "30" (for 20ms and 30ms mode + * respectively). + * + * Here is an example to set up #pjmedia_codec_param to use mode 20ms: + * \code + pjmedia_codec_param param; + ... + // setting iLBC mode in SDP + param.setting.dec_fmtp.cnt = 1; + param.setting.dec_fmtp.param[0].name = pj_str("mode"); + param.setting.dec_fmtp.param[0].val = pj_str("20"); + ... + \endcode + * + * + * \section pjmedia_codec_passthrough_amr Passthrough AMR + * + * 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. + * + * \subsection codec_setting Codec Settings + * + * General codec settings for this codec such as VAD and PLC can be + * manipulated through the <tt>setting</tt> field in #pjmedia_codec_param. + * Please see the documentation of #pjmedia_codec_param for more info. + * + * \subsubsection bitrate 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 <tt>info::avg_bps</tt> of + * #pjmedia_codec_param. Valid bitrates could be seen in + * #pjmedia_codec_amrnb_bitrates. + * + * \subsubsection payload_format 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). + * + * \subsubsection mode_set 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: + \code + pjmedia_codec_param param; + + pjmedia_codec_mgr_get_default_param(.., ¶m); + ... + // 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(.., ¶m); + \endcode + * + * + * \section pjmedia_codec_passthrough_g711 Passthrough G.711 + * + * The G.711 is an ultra low complexity codecs and in trade-off it results + * in high bitrate, i.e: 64kbps for 16-bit PCM with sampling rate 8000Hz. + * + * The factory contains two main compression algorithms, PCMU/u-Law and + * PCMA/A-Law. + * + * \subsection codec_setting Codec Settings + * + * General codec settings for this codec such as VAD and PLC can be + * manipulated through the <tt>setting</tt> field in #pjmedia_codec_param. + * Please see the documentation of #pjmedia_codec_param for more info. */ PJ_BEGIN_DECL @@ -78,7 +249,7 @@ PJ_DECL(pj_status_t) pjmedia_codec_passthrough_init( pjmedia_endpt *endpt ); * with only specified encoding formats enabled. * * @param endpt The pjmedia endpoint. - * @param setting The settings, see @pjmedia_codec_passthrough_setting. + * @param setting The settings. * * @return PJ_SUCCESS on success. */ |