On Tue, 12 Apr 2011, Ronald S. Bultje wrote:
> On Tue, Apr 12, 2011 at 3:44 AM, Martin Storsjö <mar...@martin.st> wrote:
> > ---
> > libavcodec/libvo-aacenc.c | 18 ++++++++++--------
> > 1 files changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/libavcodec/libvo-aacenc.c b/libavcodec/libvo-aacenc.c
> > index 3c7dde7..7c1738d 100644
> > --- a/libavcodec/libvo-aacenc.c
> > +++ b/libavcodec/libvo-aacenc.c
> > @@ -62,12 +62,6 @@ static av_cold int aac_encode_init(AVCodecContext *avctx)
> > return AVERROR_UNKNOWN;
> > }
> >
> > - avctx->extradata_size = 2;
> > - avctx->extradata = av_mallocz(avctx->extradata_size +
> > - FF_INPUT_BUFFER_PADDING_SIZE);
> > - if (!avctx->extradata)
> > - return AVERROR(ENOMEM);
> > -
> > for (index = 0; index < 16; index++)
> > if (avctx->sample_rate == ff_mpeg4audio_sample_rates[index])
> > break;
> > @@ -76,8 +70,16 @@ static av_cold int aac_encode_init(AVCodecContext *avctx)
> > avctx->sample_rate);
> > return AVERROR_NOTSUPP;
> > }
> > - avctx->extradata[0] = 0x02 << 3 | index >> 1;
> > - avctx->extradata[1] = (index & 0x01) << 7 | avctx->channels << 3;
> > + if (avctx->flags & CODEC_FLAG_GLOBAL_HEADER) {
> > + avctx->extradata_size = 2;
> > + avctx->extradata = av_mallocz(avctx->extradata_size +
> > + FF_INPUT_BUFFER_PADDING_SIZE);
> > + if (!avctx->extradata)
> > + return AVERROR(ENOMEM);
> > +
> > + avctx->extradata[0] = 0x02 << 3 | index >> 1;
> > + avctx->extradata[1] = (index & 0x01) << 7 | avctx->channels << 3;
> > + }
> > return 0;
> > }
>
> This isn't really what the flag means. If it's data that can be
> discarded at choice, then the flag can be ignored. Formats that don't
> like it, simply don't set extradata.
>
> The idea of the flag is that it creates extradata if set, and then not
> interleave that same data in the bitstream, and if the flag is not
> set, it interleaves that extradata in the bitstream instead. This
> patch doesn't appear to do that, so then it's not necessary...
Yes, we do that already, by enabling ADTS if the global header flag isn't
set - the ADTS header contains the same data (but is produced by the
encoder library when the adtsUsed flag is set). But if the global header
flag isn't set, we perhaps shouldn't produce any extradata at all.
Does anyone else have an opinion, or even better, insight into whether it
actually is ok to produce extradata even if the global header flag isn't
set? The data set in the extradata is MPEG4 Audio Specific Config - I
don't think it makes sense to output such extradata while outputting ADTS
data.
// Martin
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