[FFmpeg-devel] [PATCH] h264/aac in flv

[Michael Niedermayer]

On Tue, May 06, 2008 at 07:31:53PM +0200, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> >>>>>> [...]
> >>>>>>  
> >>>>>>  static int get_audio_flags(AVCodecContext *enc){
> >>>>>>      int flags = (enc->bits_per_sample == 16) ? FLV_SAMPLESSIZE_16BIT : FLV_SAMPLESSIZE_8BIT;
> >>>>>>  
> >>>>>> +    if (enc->codec_id == CODEC_ID_AAC) // specs force these parameters
> >>>>>> +        return FLV_CODECID_AAC | FLV_SAMPLERATE_44100HZ | FLV_SAMPLESSIZE_16BIT | FLV_STEREO;
> >>>>> Is this also correct for AAC streams for which these arent true? Or are
> >>>>> such streams just not supported?
> >>>>>
> >>>> Streams are supported (like mp3 48khz btw), and play well. Like written,
> >>>> specs mandates these values.
> >>> I know but what about lets say 48khz AAC or 22khz AAC your code would mux this
> >>> with a claimed samplerate of 44khz.
> >>> Is such 22khz AAC and 48khz AAC legal in flv accoridng to spec or is just
> >>> 44khz AAC allowed?
> >>> If later then the muxer should reject AAC with samplerates differing from 
> >>> 44khz.
> >>>
> >> Rofl:
> >> "Sampling rate
> >> For AAC: always 3"
> >>
> >> Is this ok for you ?
> > 
> > Ive not doubted that this has to be set to 3. The question is if
> > 48khz/22khz AAC is allowed in flv or not. If one takes the spec literally
> > then the awnser is clearly no.
> 
> Well, I would say it is probably yes, considering aac and
> AudioSpecificConfig.
> 
> > But your muxer would store them blindly
> > with a claimed sample rate of 44khz.
> 
> Well, what can I say ? It's not clearly mentioned.
> I fear they used the same crap as mp4, AudioSpecificConfig mentions the
> correct sample rate and channels number.
> This is the case for channels too:
> 
> "SoundType UB[1]
> 0 = sndMono
> 1 = sndStereo
> Mono or stereo sound
> For Nellymoser: always 0
> For AAC: always 1"
> 
> Im in favor of muxing this way.

Iam ok with that if the official software also generates such 22/48khz AAC.

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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