[FFmpeg-devel] [RFC] flvenc: missing aac extradata

[Michael Niedermayer]

On Sat, Apr 20, 2013 at 12:46:56AM +0900, Yusuke Nakamura wrote:
> 2013/4/20 Michael Niedermayer <michaelni at gmx.at>
> 
> > On Thu, Dec 13, 2012 at 02:54:56PM +0100, Björn Axelsson wrote:
> > > Problem found when remuxing mpegts (h264 + aac) to flv across pipes,
> > > like this:
> > > ffmpeg -f mpegts -i - -absf aac_adtstoasc -acodec copy -vcodec copy -f
> > flv -
> > >
> > > The AAC extradata is needed for the FLV header in flv_write_header(),
> > > but is not available at that time. This results in unusable audio in the
> > > resulting FLV stream.
> > >
> > > We currently use something like the attached patch as a workaround, but
> > > I'm sure someone can point me towards a better solution.
> >
> > how can the problem be reproduced?
> > flv does not seem to support 48khz and all aac in ts i could find is
> > 48khz
> >
> 
> FLV supports 48kHz AAC.
> 
> Quote:
> Adobe Flash Video File Format Specification Version 10.1
> E.4.2.1 AUDIODATA
> If the SoundFormat indicates AAC, the SoundType should be 1 (stereo) and
> the SoundRate should be 3 (44 kHz).
> However, this does not mean that AAC audio in FLV is always stereo, 44 kHz
> data. Instead, the Flash Player ignores
> these values and extracts the channel and sample rate data is encoded in
> the AAC bit stream.

thanks, i had been confused by our muxer refusing the 48khz aac in ts
i tried. looking closer it was actuall a aac_latm. 48khz aac gets
muxed successfully into flv.
Though it gets demuxed as 44.1khz, does someone have a known to be
valid 48khz aac in flv file ? (so i can check if its our muxer
not storing it correctly or demuxer not recognizing 48khz)

Thanks

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

There will always be a question for which you do not know the correct answer.
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