[FFmpeg-trac] #5027(avcodec:new): avcodec_free_context frees extradata

[FFmpeg]

#5027: avcodec_free_context frees extradata
-----------------------------------+---------------------------------------
             Reporter:  jyavenard  |                     Type:  defect
               Status:  new        |                 Priority:  normal
            Component:  avcodec    |                  Version:  unspecified
             Keywords:             |               Blocked By:
             Blocking:             |  Reproduced by developer:  0
Analyzed by developer:  0          |
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 According to the AVCodecContext specification:

 AVCodecContext::extradata is "decoding: Set/allocated/freed by user. "

 only for encoding is extradata managed by avcodec.

 And avcodec_close does the right thing, and only free extradata field if
 the AVCodecContext instantiated an encoder.

 However, avcodec_free_context always free extradata if set:

 {{{
 void avcodec_free_context(AVCodecContext **pavctx)
 {
     AVCodecContext *avctx = *pavctx;

     if (!avctx)
         return;

     avcodec_close(avctx);

     av_freep(&avctx->extradata);
     av_freep(&avctx->subtitle_header);
     av_freep(&avctx->intra_matrix);
     av_freep(&avctx->inter_matrix);
     av_freep(&avctx->rc_override);

     av_freep(pavctx);
 }
 }}}

 This is incorrect, it assumes that the ownership of extradata is by
 avcodec for either the decoder or the encoder.

 Now the problem has been there for quite a while and it may be too late.

 As such, either avcodec_free_context should be made obsolete and replaced
 with avcodec_free_context2 which would do the right thing.

 Or the documentation needs to be updated, and the ownership of extradata
 now being by avcodec, this assumes that avcodec_close would also free
 extradata.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5027>
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