[FFmpeg-devel] [PATCH] avcodec thread safety fix

Daniel Steinberg daniel
Tue May 12 22:56:39 CEST 2009

2009/5/12 M?ns Rullg?rd <mans at mansr.com>:
> Daniel Steinberg <daniel at InstantHarmony.com> writes:
>> Although avcodec_open/avcodec_close are known to have thread-safety
>> issues (hence the entangled_thread_counter), it is not sufficient in a
>> multi-threaded environment to simply protect calls to them with a
>> mutex, because av_find_stream_info() internally calls them as well.
>> Further, av_find_stream_info() may subsequently block for input, so it
>> is not a good idea to hold a mutex for the duration of its call.
>> Attached is a proposed fix that allows clients to specify a locking
>> routine that, if non-NULL, will be called by avcodec_open() and
>> avcodec_close(), thereby protecting them from re-entrancy regardless
>> of the calling source.
> Your patch does not solve the problem you describe. ?How would the
> callback get set for the calls from av_find_stream_info()?

It is up to the caller to set the callback(s) before calling
av_find_stream_info() (and, of course, avcodec_open/close), eg:

int MyFindStreamInfo(AVFormatContext *ic) {
  for (int i = 0; i < ic->nb_streams; ++i) {
    ic->streams[i]->codec->codec_mutex_cb = MyMutexCallback;
  return av_find_stream_info(ic);

> --
> M?ns Rullg?rd
> mans at mansr.com
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel

More information about the ffmpeg-devel mailing list