[FFmpeg-devel] Allow interrupt callback for AVCodecContext

[Don Moir]

For now just seeing what you think about this. This is about thread based apps where this makes sense.

When attempting to do a new seek or waiting to close a video, I find that I am waiting on avcodec_decode_video2 to return before I can continue. Depending on machine and video, this wait time can be up to about 50ms but normally wait time about 5 to 20 ms or so.

You might say 'so what' and I would agree for a simple player app it does not make that much difference.

If you are trying to stay on a timeline, or in case of scrubbing, or for editing apps, this wait time does make a difference. That is, you can not move on until avcodec_decode_video2 has returned.

I can pretty much seek instantly to zero for any file except when I have to wait on avcodec_decode_video2 if that be the case.

For me, it's normal for any intense process like decoding to be interruptible but this is not the case for AVCodecContext in ffmpeg. This is strange, don't you think?

For AVFormatContext you have:

typedef struct AVIOInterruptCB {
    int (*callback)(void*);
    void *opaque;
} AVIOInterruptCB;

I would use this model for AVCodecContext but change naming to:

typedef struct AVInterruptCB {
    int (*callback)(void*);
    void *opaque;
} AVInterruptCB;

Then make name changes to whereever and add to AVCodecContext.

This callback could be implemented piecemeal whereever needed over time, hitting the more intense processes first.