[mythtv-commits] Ticket #13186: Replace deprecated ffmpeg functions

[MythTV]

#13186: Replace deprecated ffmpeg functions
------------------------------+-----------------------------
 Reporter:  pbennett          |          Owner:  pbennett
     Type:  Developer Task    |         Status:  accepted
 Priority:  minor             |      Milestone:  30.0
Component:  MythTV - General  |        Version:  Master Head
 Severity:  medium            |     Resolution:
 Keywords:                    |  Ticket locked:  0
------------------------------+-----------------------------

Comment (by pbennett):

 Patch 005 - deprecated AVStream::codec and avcodec_close

 In the old method, ffmpeg automatically creates an AVCodecContext for
 every AVStream. The context can be opened and closed again any number of
 times. This is deprecated and the application code is now responsible for
 creating and freeing an  AVCodecContext when needed. The  AVCodecContext
 that the application creates may not be opened and closed more than once.
 The deprecated function avcodec_close must not be called on an
 AVCodecContext that you create, instead you have to free the
 AVCodecContext (using avcodec_free_context) and allocate a new one if you
 want to read the stream again.

 "codec" no longer shows in the online documentation for AVStream. It is
 only defined in ffmpeg if you define FF_API_LAVF_AVCTX when compiling
 ffmpeg. See external/FFmpeg/libavformat/version.h, which has a list of
 defines that will be set in future to disable this and others. For more
 information google FF_API_LAVF_AVCTX. Instead of AVStream::codec, the
 AVStream::codecpar structure contains the information you need to allocate
 your own AVStream.

 Old code for AVStream::codec
 {{{
 AVCodecContext *avctx = stream->codec;
 }}}

 new code using AVStream::codecpar
 {{{
 AVCodec *pCodec = avcodec_find_decoder(stream->codecpar->codec_id);
 AVCodecContext *avctx = avcodec_alloc_context3(pCodec);
 avcodec_parameters_to_context(avctx, stream->codecpar);
 av_codec_set_pkt_timebase(avctx, stream->time_base);
 }}}
 The avctx must saved and the same value used for subsequent calls with
 that stream. Existing code which uses stream->codec must instead keep
 track of the axctx value to use each time a packet is received.

 Old Code for avcodec_close:
 {{{
 avcodec_close(st->codec);
 }}}

 New code using avcodec_free_context:
 {{{
 avcodec_free_context(&avctx);
 }}}
 Note the old code must still be used for any AVCodecContext obtained from
 stream->codec.

 DVD menu highlighting on the title menu has been working intermittently
 for some time. That makes it very difficult to navigate a DVD. It seems to
 be working consistently correctly after these changes, although I could
 not identify which change made the difference.

 The patch is tested with Standard decoding(ffmpeg), VAAPI, VDPAU, OpenMAX
 (Raspberry pi). Tested playback of recordings, Live TV, Videos, DVD's'.

 Some areas not yet changed and not tested. In particular, crystal HD,
 Windows, and Apple MAC playback may not work. Also transcode has not yet
 been updated.

--
Ticket URL: <https://code.mythtv.org/trac/ticket/13186#comment:5>
MythTV <http://www.mythtv.org>
MythTV Media Center