[FFmpeg-devel] [PATCH] avcodec/mediacodecdec: call MediaCodec.stop on close
Zhao Zhili
quinkblack at foxmail.com
Fri Aug 9 05:17:58 EEST 2024
> On Aug 9, 2024, at 02:14, sfan5 <sfan5 at live.de> wrote:
>
> Am 08.08.24 um 17:29 schrieb Zhao Zhili:
>>> On Aug 8, 2024, at 00:27, sfan5<sfan5 at live.de> wrote:
>>>
>>> Hi all,
>>>
>>> attached is a small fix for the MediaCodec code. Tested on Android 14.
>>>
>>> This can free up vital resources in case of using multiple
>>> decoding instances and there are buffer references left over
>>> and not immediately cleaned up.
>>>
>>> Signed-off-by: sfan5<sfan5 at live.de>
>>> ---
>>> libavcodec/mediacodecdec_common.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/libavcodec/mediacodecdec_common.c b/libavcodec/mediacodecdec_common.c
>>> index d6f91e6e89..c888dea8cf 100644
>>> --- a/libavcodec/mediacodecdec_common.c
>>> +++ b/libavcodec/mediacodecdec_common.c
>>> @@ -841,6 +841,18 @@ int ff_mediacodec_dec_flush(AVCodecContext *avctx, MediaCodecDecContext *s)
>>> int ff_mediacodec_dec_close(AVCodecContext *avctx, MediaCodecDecContext *s)
>>> {
>>> + if (!s)
>>> + return 0;
>>> +
>>> + if (s->codec) {
>>> + if (atomic_load(&s->hw_buffer_count) == 0) {
>>> + ff_AMediaCodec_stop(s->codec);
>>> + av_log(avctx, AV_LOG_DEBUG, "MediaCodec %p stopped\n", s->codec);
>>> + } else {
>>> + av_log(avctx, AV_LOG_DEBUG, "Not stopping MediaCodec (there are buffers pending)\n");
>>> + }
>>> + }
>>> +
>> Could you elaborate on how this resolved the issue?
>> If hw_buffer_count is zero, isn’t MediaCodecDecContext will be released immediately?
>> If hw_buffer_count isn’t zero, the patch make no real change, so how does this patch work?
>
> Sure.
>
> here's the original report: https://github.com/mpv-android/mpv-android/issues/966
>
> summary:
>
> mpv's hwdec code uses a single surface to facilitate zero-copy video playback. Keeping an active MediaCodec instance connected to the surface blocks the same surface from being used with a different MediaCodec instance.
>
> However mpv also keeps a reference to the last rendered frame alive even when switching between files. It also flushes the codec when it's done with a file. This leads to a situation where hw_buffer_count == 0 && refcount > 1.
>
> If you were to say that this should be fixed in mpv I would agree and I have indeed proposed a PR for this. But I noticed we're never calling stop() in mediacodecdec and it's a very simple remedy.
OK. Please add the background to the commit message. It’s not obvious how to trigger the "hw_buffer_count == 0 && refcount > 1” case.
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