[FFmpeg-devel] [PATCH v2 06/10] avcodec/aptx: Use AVCodecContext.frame_size according to the API

[Hendrik Leppkes]

On Tue, Aug 31, 2021 at 4:22 PM Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>
> On Tue, Aug 31, 2021 at 2:44 PM Andreas Rheinhardt
> <andreas.rheinhardt at outlook.com> wrote:
> >
> > Currently the APTX (HD) codecs set frame_size if unset and check
> > whether it is divisible by block_size (corresponding to block_align
> > as used by other codecs). But this is based upon a misunderstanding
> > of the API: frame_size is not in bytes, but in samples.*
> >
> > Said value is also not intended to be set by the user at all,
> > but set by encoders and (possibly) decoders if the number of channels
> > in a frame is constant. The latter condition is not fulfilled here,
> > so only set it for encoders to the value that it already had for APTX:
> > 1024 samples (per channel).
> >
> > *: If it were needed to check said value, one would need to check
> > for it to be divisible by four (four samples correspond to one block
> > of block_size bytes).
> >
> > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> > ---
> >  libavcodec/aptx.c | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/libavcodec/aptx.c b/libavcodec/aptx.c
> > index 3aeee1907c..97397aca68 100644
> > --- a/libavcodec/aptx.c
> > +++ b/libavcodec/aptx.c
> > @@ -515,14 +515,8 @@ av_cold int ff_aptx_init(AVCodecContext *avctx)
> >      s->hd = avctx->codec->id == AV_CODEC_ID_APTX_HD;
> >      s->block_size = s->hd ? 6 : 4;
> >
> > -    if (avctx->frame_size == 0)
> > -        avctx->frame_size = 256 * s->block_size;
> > -
> > -    if (avctx->frame_size % s->block_size) {
> > -        av_log(avctx, AV_LOG_ERROR,
> > -               "Frame size must be a multiple of %d samples\n", s->block_size);
> > -        return AVERROR(EINVAL);
> > -    }
> > +    if (av_codec_is_encoder(avctx->codec))
> > +        avctx->frame_size = 1024;
> >
>
> s->block_size can be 6 for HD or 4 for non-HD, making the default
> frame_size not always 1024 before this change, thus a change in
> behavior for aptx HD. Is this intended?
>

Nevermind, I now figured out what your commit message means. It wasn't
extremely clear.

- Hendrik