[FFmpeg-devel] [PATCH] avcodec/mpegaudiodec_template: skip first frame after seeking

[Michael Niedermayer]

On Fri, Apr 17, 2015 at 07:21:23PM +0200, wm4 wrote:
> On Fri, 17 Apr 2015 19:04:02 +0200
> Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > This could be made optional if preferred
> > ---
> >  libavcodec/mpegaudiodec_template.c |    7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/libavcodec/mpegaudiodec_template.c b/libavcodec/mpegaudiodec_template.c
> > index 2326a90..70c17a1 100644
> > --- a/libavcodec/mpegaudiodec_template.c
> > +++ b/libavcodec/mpegaudiodec_template.c
> > @@ -87,6 +87,7 @@ typedef struct MPADecodeContext {
> >      MPADSPContext mpadsp;
> >      AVFloatDSPContext *fdsp;
> >      AVFrame *frame;
> > +    int flushed;
> >  } MPADecodeContext;
> >  
> >  #define HEADER_SIZE 4
> > @@ -1645,6 +1646,11 @@ static int mp_decode_frame(MPADecodeContext *s, OUT_INT **samples,
> >          }
> >      }
> >  
> > +    if (s->flushed) {
> > +        s->avctx->internal->skip_samples = FFMAX(s->avctx->internal->skip_samples, s->frame->nb_samples);
> > +        s->flushed = 0;
> > +    }
> > +
> >      return nb_frames * 32 * sizeof(OUT_INT) * s->nb_channels;
> >  }
> >  
> > @@ -1723,6 +1729,7 @@ static void mp_flush(MPADecodeContext *ctx)
> >      memset(ctx->mdct_buf, 0, sizeof(ctx->mdct_buf));
> >      ctx->last_buf_size = 0;
> >      ctx->dither_state = 0;
> > +    ctx->flushed = 1;
> >  }
> >  
> >  static void flush(AVCodecContext *avctx)
> 
> Would this not break gapless audio if you seek back to the first frame
> after being done decoding? (Consider usecases like infinite looping.)

i did not test it but the skip value from AVPacket should override
this if its set
the first packet should contain skip sidedata or the mp3 would start
with a "half" empty output frame

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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