On the SDP layer, the audio format parameters a=fmtp for AMR (and AMR-WB) may include a set of modes allowed in the call. The current code of res_format_attr_amr parses the supported set in amr_parse_sdp_fmtp(.). And initializes the transcoding module with the last mode presented by the remote party. However, the last mode may not be the highest. For example:
mode-set=0,2,5,7
mode-set=7,5,2,0
are both expected to initialize the mode_current to 7. Currently, the first case gets mode 7; the second case gets mode 0.
However, this affects only internal calls which do not pass amr_getjoint(.).
However, no existing AMR implementation is known to send the modes not ascending. All known implementations send either
(a) no mode-set at all, or
(b) a single mode in the mode-set, or
(c) an ascending mode-set, like case 1.
Although this should not affect anyone, the issue was found in an internal code review.
On the SDP layer, the audio format parameters
a=fmtpfor AMR (and AMR-WB) may include a set of modes allowed in the call. The current code ofres_format_attr_amrparses the supported set inamr_parse_sdp_fmtp(.). And initializes the transcoding module with the last mode presented by the remote party. However, the last mode may not be the highest. For example:mode-set=0,2,5,7mode-set=7,5,2,0are both expected to initialize the
mode_currentto 7. Currently, the first case gets mode 7; the second case gets mode 0.However, this affects only internal calls which do not pass
amr_getjoint(.). However, no existing AMR implementation is known to send the modes not ascending. All known implementations send either (a) no mode-set at all, or (b) a single mode in the mode-set, or (c) an ascending mode-set, like case 1.Although this should not affect anyone, the issue was found in an internal code review.