On Sun, 27 Aug 1995, Thomas Grant Edwards wrote:
There is a standards track for real-time audio and video communications. Seems to me the hard part is defining codecs, the easy part is dropping in crypto.
See ftp://gaia.cs.umass.edu/pub/hgschulz/rtp/draft-ietf-avt-rtp-06.txt for more information on the RTP standard. See ftp://gaia.cs.umass.edu/pub/hgschulz/rtp/draft-ietf-avt-profile-04.txt for the use of RTP in video and audio conferencing. This draft recommends the following audio encodings: name nom. sampling rate type frame description Hz kb/s S/F ms _________________________________________________________________________ L8 11025 88.2 S 8-bit linear, offset L16 48000 768 S 16-bit linear, 2's complement L16 44100 705.6 S L16 22050 352.8 S L16 11025 176.4 S G722 16000 64 S CCITT/ITU-T subband ADPCM PCMU 8000 64 S CCITT/ITU-T mu-law PCM PCMA 8000 64 S CCITT/ITU-T A-law PCM G721 8000 32 S CCITT/ITU-T ADPCM IDVI 8000 32 S Intel/DVI ADPCM [IMA] IDVI 16000 64 S Intel/DVI ADPCM [IMA] G723 8000 24 S CCITT/ITU-T ADPCM GSM 8000 13 F 20 RTE/LTP GSM 06.10 1016 8000 4.8 F 30 CELP _________________________________________________________________________ Some of these seem perfectly appropriate for 28.8 kbps transmission, even with the overhead of a PPP dialup connection.