M4 Supported Codecs
From Kolmisoft Wiki
As M4 uses RTPEngine as a Media Proxy, supported codecs are:
rtpengine --codecs PCMA: fully supported PCMU: fully supported G723: fully supported G722: fully supported QCELP: supported for decoding only G729: fully supported G729a: fully supported speex: fully supported GSM: fully supported iLBC: not supported opus: fully supported vorbis: codec supported but lacks RTP definition ac3: codec supported but lacks RTP definition eac3: codec supported but lacks RTP definition ATRAC3: supported for decoding only ATRAC-X: supported for decoding only AMR: fully supported AMR-WB: fully supported telephone-event: fully supported CN: fully supported PCM-S16LE: codec supported but lacks RTP definition PCM-U8: codec supported but lacks RTP definition MP3: codec supported but lacks RTP definition