[FFmpeg-trac] #7251(avcodec:new): Memory/Resource Leak in avcodec_open2() on failure

FFmpeg trac at avcodec.org
Fri Jun 8 22:03:59 EEST 2018

#7251: Memory/Resource Leak in avcodec_open2() on failure
             Reporter:  jlsantiago0  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avcodec      |                  Version:  git-
             Keywords:  memory       |  master
  leak, resource leak                |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 When calling avcodec_open2(), memory and other resources can leak if the
 encoder init fails or other steps within the codec open function fails.
 This includes memory and threads that can be created, but not destroyed in
 the case of a failure.

 For instance, if you attempt to intialize an MPEG2 Video Encoder and
 enable slice based threaded encoding. If you do not set the resolution,
 fps, or the pixel format to a valid value. The encoder inititialization
 will fail, indicating that the codec context parameter is invalid for the
 selected encoder. It properly returns an error. But it does not destroy
 the threads it created. Nor does it destory all of the memory that the
 encoder init allocated before returning the failure.

 For instance you can run valgrind with the following program to
 demonstrate the problem:

 #include <libavcodec/avcodec.h>
 #include <libavutil/avassert.h>

 int main(void)
    AVCodec * codec;
    AVCodecContext * avctx;

    codec = avcodec_find_encoder(AV_CODEC_ID_MPEG2VIDEO);
    av_assert0(codec != NULL);
    avctx = avcodec_alloc_context3(codec);
    av_assert0(avctx != NULL);

    // Basic configuration
    // You can get the results by setting the pix_fmt
    // and/or resolution to some invalid or unsupported value.
    avctx->pix_fmt = AV_PIX_FMT_YUV420P;
    avctx->width = 640;
    avctx->height = 480;
    // Set some ffps that is not supported by MPEG2 Video
    avctx->time_base.num = 91;
    avctx->time_base.den = 2201;
    avctx->ticks_per_frame = 1;
    // Enable slice thread encoding
    avctx->thread_count = 10;
    avctx->thread_type = 2;
    avctx->active_thread_type = 2;

    // Open the Codec for encoding
    avcodec_open2(avctx, codec, NULL);

    // close and free the Codec

 NOTE: If you put contents of main() in a loop to run forever, it will
 eventually make your system unstable as the number of threads created and
 not destroyed by the program exceed the number of supported threads in the

Ticket URL: <https://trac.ffmpeg.org/ticket/7251>
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