> On Aug. 5, 2014, 1:03 p.m., Joshua Colp wrote: > > Can you elaborate on what actually happens here between 11<->12 and 12<->12 > > that makes it so we need to remove the newly added ones? > > rmudgett wrote: > The format compatibility bits need to remain frozen to new codecs because > chan_iax2 leaks internal implementation values and doesn't know how to > negotiate any codec options. Opus has options can be negotiated. I don't > know about VP8 but as its a newer codec it likely has negotiable options. > > The IAX_IE_CODEC_PREFS body is a sequence of 8 bit values. In v1.8 and > earlier the preference values are the index+1 into the > frame.c:AST_FORMAT_LIST[]. In v10-v11 the preference values are the order > that formats are put into the format_list ao2 list conatiner in > format.c:format_list_init(). The format_list is then converted to the > format_list_array object and indexed like AST_FORMAT_LIST[]. For backwards > compatibility, the first 28 match the order in v1.8's AST_FORMAT_LIST[] and > have format compatibility bits assigned. There is a comment saying the order > of the first 28 must not change. The comment does not state why. However, > that order cannot change because those formats are in the historical > AST_FORMAT_LIST[], those formats have compatibility bits, and the index > values are sent over the wire by IAX2. After the fixed formats there is a > comment saying the order may change. The comment does not state why. > However, the order may change because none of the following fo rmats have a format combatibility bit defined. In v12 the Opus and VP8 formats were added to the format_list eight formats after the end of the fixed formats and also assigned format compatibility bits. > > Interoperation between v12 and earlier Asterisk version should not be a > problem because earlier versions doesn't know about Opus and VP8 and thus > won't pick those codecs. > > Between v12 instances, Opus and VP8 could be picked. However, because of > their order in the format_list there will be a gap of eight between G719 and > Opus that will be difficult to maintain without dire comments that won't be > followed. Also as stated, IAX2 doesn't know how to negotiate any codec > options.
It's fine to not negotiate attributes, it just yields a subpar experience in many cases. By removing these from 12 we're essentially removing something that people could have used. I'm not okay with that. - Joshua ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviewboard.asterisk.org/r/3889/#review12982 ----------------------------------------------------------- On Aug. 4, 2014, 10:47 p.m., rmudgett wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviewboard.asterisk.org/r/3889/ > ----------------------------------------------------------- > > (Updated Aug. 4, 2014, 10:47 p.m.) > > > Review request for Asterisk Developers. > > > Repository: Asterisk > > > Description > ------- > > The format compatibility bits need to remain frozen to new codecs. > Otherwise, older channel drivers like chan_iax2 could attempt to negotiate > them when they have no support for negotiating any of the format's other > potential parameters. In addition, the chan_iax2 format preference order > values sent over the wire have no defined fixed value to represent Opus and > VP8. > > > Diffs > ----- > > /branches/12/main/format.c 420025 > > Diff: https://reviewboard.asterisk.org/r/3889/diff/ > > > Testing > ------- > > Compiles and code inspeciton. > > See format.c:format_list_init() and format_pref.c:ast_codec_pref_convert(). > The format_list container is used to generate the format_list_array which is > then is used by chan_iax2 to determine the format index sent over the wire in > IAX_IE_CODEC_PREFS. > > > Thanks, > > rmudgett > >
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