On Thu, Dec 2, 2021, at 15:05, Andreas Rheinhardt wrote: > 1. hw_device_ctx is in the public AVCodecContext, not in the private > AVCodecInternal. > 2. ctx->internal is intended to be allocated for all the internal > AVCodecContexts; the check is only there to ensure that we don't crash > if an allocation error happens. > 3. libavcodec only ever modifies avctx->hw_device_ctx at one place: in > avcodec_close() where is unreferences the reference (if any). So if it > was set in avcodec_open2() and NULL in avcodec_close() (i.e. immediately > before avcodec_close()), it has been modified somehow and you need to > find out who did it. > 4. Some parts of the code use hw_device_ctx to derive references from > it. Maybe one of these references did not get freed? > (5. What do Valgrind/ASAN say? When was the reference that leaked created?)
OK, all your point are valid, I missed a precious comment from the avcodec.h API: "For both encoders and decoders this field should be set before avcodec_open2() is called and must not be written to thereafter." Hence, the incomprehension. So, to sum up: the reference that leaks is created from VLC, from the get_format() callback. Looking at pthread_frame.c, it seems that get_format() is called with a AVCodecContext owned by a PerThreadContext, so not the main AVCodecContext. That is why avcodec_close() is not closing it. I just discovered that it's not officially supported then, but I really don't see any other way to plug VAAPI between VLC and ffmpeg. I explain: VLC can't know the hw_device that will be used when it calls avcodec_open2(). VLC has a similar struct than hw_device, called dec_device. For VAAPI, this struct hold the va_dpy that is created when the VLC avcodec module first create the video output, from the get_format() callback. I see 2 possibilities: 1/ Patch the documentation and allow to set a hw_device_ctx from get_format(), review all use case of hw_device_ctx to check if there is no inconsistency with this new change. 2/ Use any other way to pass the va_dpy from the get_format()? I didn't see any, but maybe I missed something obvious. Best, Thomas > > - Andreas > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
