On Thu, 5 Nov 2015 22:38:14 +1300 Jean-Yves Avenard <[email protected]> wrote:
> On 3 November 2015 at 21:04, Info || Non-Lethal Applications > <[email protected]> wrote: > > > > > I just grabbed the latest 1.8.1 source code and I don’t see any flag to > > toggle async decoding. > > I only see that the function videotoolbox_session_decode_frame waits for the > > asynchronously decoded frames using > > VTDecompressionSessionWaitForAsynchronousFrames. > > Is the waiting part what you mean? > > I have no experience in using VT via ffmpeg, I've only ever accessed > VT directly (wrote the Firefox h264 decoder on mac) > > The async flag (kVTDecodeFrame_EnableAsynchronousDecompression) is > provided to VTDecompressionSessionDecodeFrame > > In my personaly experience, not turning that flag, and instead waiting > for the frame with VTDecompressionSessionWaitForAsynchronousFrames > immediately leads to severe performance issue. > To the point where you typically get better performance using the > ffmpeg sofware decoder > > This is even more true on mac not supporting HW decode (in particular > late-2013 mac pro) > > > > > Do you have any insight why this is not used for Pro Res decoding? > > most likely because the FFmpeg avcodec_decode_video2 is synchronous. > There's no straight forward mechanism to have callbacks returning > frames at a later point. > Not that it can't be done. There are diffuse plans to introduce async decoding to FFmpeg (both API, and Videotoolbox), but nothing concrete yet. _______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
