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audio: use idiotic FFmpeg ABI rules for public-except-not-public fields

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The FFmpeg API is incredibly weird and inconsistent about this. This is
also a FFmpeg-only issue and nothing like this is in Libav - which
doesn't really show FFmpeg in a very positive light.

(To make it even worse: this is a full-blown Libav API incompatibility,
even though this crap was added for Libav ABI-compatibility. It's
absurd.)

Quoting the FFmpeg header for the AVFrame.channels field:

    /**
     * number of audio channels, only used for audio.
     * Code outside libavutil should access this field using:
     * av_frame_get_channels(frame)
     * - encoding: unused
     * - decoding: Read by user.
     */
    int channels;

It says "should" not must, and it doesn't even mention
av_frame_set_channels(). It's also in the section for public fields (not
below a marker that indicates private fields in a public struct, like
it's done e.g. in AVCodecContext).

But not using the accessor will cause silent failures on ABI changes.
The failure that happened due to this code didn't even make it apparent
what was wrong. So just use the idiotic accessor.

Also harmonize the FFmpeg-cursing in the code. (It's fully justified.)

Fixes #3295.

Note that mpv will still check the exact library version numbers, and
reject mismatches - to protect itself from such issues in the future.
This commit is contained in:
wm4 2016-07-24 19:31:47 +02:00
parent 6bb48a10db
commit dcfde2934d
1 changed files with 5 additions and 5 deletions
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10
audio/audio.c
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@ -347,9 +347,9 @@ struct mp_audio *mp_audio_from_avframe(struct AVFrame *avframe)
mp_chmap_from_lavc(&lavc_chmap, avframe->channel_layout);
#if LIBAVUTIL_VERSION_MICRO >= 100
// FFmpeg being special again
if (lavc_chmap.num != avframe->channels)
mp_chmap_from_channels(&lavc_chmap, avframe->channels);
// FFmpeg being stupid POS again
if (lavc_chmap.num != av_frame_get_channels(avframe))
mp_chmap_from_channels(&lavc_chmap, av_frame_get_channels(avframe));
#endif
new->rate = avframe->sample_rate;
@ -407,8 +407,8 @@ int mp_audio_to_avframe(struct mp_audio *frame, struct AVFrame *avframe)
if (!avframe->channel_layout)
goto fail;
#if LIBAVUTIL_VERSION_MICRO >= 100
// FFmpeg being a stupid POS (but I respect it)
avframe->channels = frame->channels.num;
// FFmpeg being a stupid POS again
av_frame_set_channels(avframe, frame->channels.num);
#endif
avframe->sample_rate = frame->rate;