On Mon, 19 May 2014 12:15:04 -0400, Bill Gardner wrote:
> [...]
> PJSIP uses the largest possible frame supported by the H264 profile
> level which also has 3/2 aspect ratio, in multiples of 16 pixels (the
> H264 macroblock size). See function find_highest_res() in
> vid_codec_util.c. So at level 3.0 PJSIP allocates a 768x512 frame,
> exactly 3/2 aspect ratio. PJSIP can resize dynamically, but only to
> smaller frame sizes. So when 4CIF comes in at 704x576 (which is a
> slightly larger image but still supported by level 3.0) PJSIP can't
> decode the video and emits error messages. Fortunately an easy
> workaround is to set the profile level to 3.1 and then PJSIP allocates a
> pretty huge frame for decoding.
Just curious, where does this imposed 3/2 aspect ratio come from?
(Has it indirectly anything to do with the default 720x480 at 15 for h264
in PJSIP as in ffmpeg_vid_codecs.c?)
If "ITU-T H.264 Appendix A.3.1 e), f), g)" is the proper document then
level 3.0 (max image size in macroblocks = 1620) should support frame
sizes (in pixels) something like from
640 x 640 (quadratic)
to
1808 x 16 (most "nonquadratic")
according to the size constraints specified there?
Does SIP/SDP pose additional restrictions?
P.S. Would anything change if the other endpoint reduces offered fps?
Eeri Kask
