On Mon, Sep 25, 2017 at 3:06 AM, wm4 <nfx...@googlemail.com> wrote: > On Mon, 25 Sep 2017 09:02:36 +0200 > Hendrik Leppkes <h.lepp...@gmail.com> wrote: > > > On Mon, Sep 25, 2017 at 3:31 AM, Aman Gupta <ffm...@tmm1.net> wrote: > > > > > > How do the other hwaccels handle mid-stream SPS changes? > > > > > > > Real HWAccels (ie. VAAPI, VDPAU or DXVA) communicate the SPS/PPS > > content for every frame, they don't keep a persistent state internally > > - that way the only "state" is the frame size and pixel format, and > > when those change get_format is called and the hwaccel re-initialized. > > Maybe it would be better if VT detected SPS/PPS changes itself, and > reinitialized the VT session on demand when feeding slices. This way we > wouldn't have to mess with the normal h264 software decoder reinit > logic. >
Agreed. I'm trying to figure out the most efficient way to detect when the SPS/PPS changes. Previously I tried feeding in the SPS/PPS NALs from the decoder into the VT hwaccel (with a new `decode_params` callback), and using that to store a copy of the NAL in the hwaccel. I used a memcmp() against the previously stored value to detect when changes occurred and restarted the decompression session according. This approach worked well, but doesn't handle some streams which use multiple PPS. The most fool-proof way would be to construct a new avcC every time and only restart the session when it changes. But that seems quite expensive to be doing all the time. I'm also still not sure if the VT decoder needs to be restarted on SPS changes only, or PPS as well. Do new PPS usually accompany a new SPS? Is it also possible to have multiple SPS used at the same time? (The avcC construction code in videotoolbox.c assumes one SPS and one or more PPS). Aman > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
