On Thu, Sep 8, 2022 at 10:26 AM <jyrk...@nekonyansoft.com> wrote:
> From: Jyrki Vesterinen <jyrk...@nekonyansoft.com>
>
> If a developer using FFmpeg libraries seeks into an earlier position and
> calls
> avcodec_flush_buffers() afterwards as recommended, the Vorbis decoder will
> drop
> the next frame, since buffer flushing clears the first_frame flag. As a
> result,
> the audio samples the calling code receives may be ahead of the requested
> seek
> position, which is unacceptable in some use cases such as playing a looping
> sound effect.
>
> This commit removes the first_frame flag entirely and instead uses the
> presentation timestamp to determine if it's the first frame.
>
Proper solution is to fetch initial/first pts and use that one instead
using of using
fragile pts < 0.
> ---
> libavcodec/vorbisdec.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
> index 4d03947c49..d4b030d7b9 100644
> --- a/libavcodec/vorbisdec.c
> +++ b/libavcodec/vorbisdec.c
> @@ -130,7 +130,6 @@ typedef struct vorbis_context_s {
> AVFloatDSPContext *fdsp;
>
> FFTContext mdct[2];
> - uint8_t first_frame;
> uint32_t version;
> uint8_t audio_channels;
> uint32_t audio_samplerate;
> @@ -1845,8 +1844,7 @@ static int vorbis_decode_frame(AVCodecContext
> *avctx, AVFrame *frame,
> if ((len = vorbis_parse_audio_packet(vc, channel_ptrs)) <= 0)
> return len;
>
> - if (!vc->first_frame) {
> - vc->first_frame = 1;
> + if (frame->pts < 0) {
> *got_frame_ptr = 0;
> av_frame_unref(frame);
> return buf_size;
> @@ -1881,7 +1879,6 @@ static av_cold void
> vorbis_decode_flush(AVCodecContext *avctx)
> sizeof(*vc->saved));
> }
> vc->previous_window = -1;
> - vc->first_frame = 0;
> }
>
> const FFCodec ff_vorbis_decoder = {
> --
> 2.37.2.windows.2
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
>
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
