[FFmpeg-trac] #10770(undetermined:new): avcodec_open2 overwrites flags contrary to what the doc says

[FFmpeg]

#10770: avcodec_open2 overwrites flags contrary to what the doc says
-------------------------------------+-------------------------------------
             Reporter:  Jean-        |                     Type:  defect
  Michaël Celerier                   |
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 The avcodec_open2 documentation states, about the options parameter:

 {{{
  * @param options A dictionary filled with AVCodecContext and codec-
 private
  *                options, which are set on top of the options already set
 in
  *                avctx, can be NULL. On return this object will be filled
 with
  *                options that were not found in the avctx codec context.
 }}}

 Yet given the following program, the final assert does not pass:
 AV_CODEC_FLAG_GLOBAL_HEADER gets overwritten in the codec context's flags.

 {{{
 extern "C" {
 #include <libavcodec/avcodec.h>
 }

 #include <cassert>
 int main()
 {
   auto codec = avcodec_find_encoder_by_name("libx264");
   auto c = avcodec_alloc_context3(codec);

   c->width = 1280;
   c->height = 720;
   c->time_base = (AVRational){100000, int(100000 * 30)};
   c->framerate = AVRational{c->time_base.den, c->time_base.num};
   c->gop_size = 0;
   c->max_b_frames = 0;
   c->pix_fmt = AV_PIX_FMT_YUV420P;
   c->strict_std_compliance = FF_COMPLIANCE_NORMAL;
   c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

   AVDictionary* opt{};
   av_dict_set(&opt, "flags", "low_delay", 0);

   avcodec_open2(c, codec, &opt);
   assert(c->flags & AV_CODEC_FLAG_GLOBAL_HEADER);
 }
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10770>
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