[FFmpeg-devel] [PATCH 03/19] adpcm: fix return value for small overreads.
Reimar.Doeffinger at gmx.de
Sun Jul 29 17:44:07 CEST 2012
On Sun, Jul 29, 2012 at 02:49:04PM +0000, Paul B Mahol wrote:
> On 7/29/12, Nicolas George <nicolas.george at normalesup.org> wrote:
> > Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
> > ---
> > libavcodec/adpcm.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> > Comment for this one and the next few:
> > I believe it is better to know what decoders rely on
> > FF_INPUT_BUFFER_PADDING_SIZE rather than catch everything in a common test,
> > but if people prefer the opposite I can drop these cases.
> > diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
> > index b86168a..6706b07 100644
> > --- a/libavcodec/adpcm.c
> > +++ b/libavcodec/adpcm.c
> > @@ -1265,7 +1265,10 @@ static int adpcm_decode_frame(AVCodecContext *avctx,
> > void *data,
> > *got_frame_ptr = 1;
> > *(AVFrame *)data = c->frame;
> > - return bytestream2_tell(&gb);
> > + ret = bytestream2_tell(&gb);
> > + if (ret > avpkt->size && ret <= avpkt->size +
> > FF_INPUT_BUFFER_PADDING_SIZE)
> > + ret = avpkt->size; /* small overreads are acceptable */
> > + return ret;
> > }
> Isn't point of bytestream2 to not overread?
> So I'm against applying this hack.
> Instead all cases where unchecked bytestream2 functions are used
> (get_be16u and similar)
> should have bytestream2_get_bytes_left.. before them.
bytestream2 costs performance, so one might not want to use it for parts
that are critical and can't overread enough to cause issues.
Though I agree that this seems a bit fishy, it would be necessary to
figure out what goes on.
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