[FFmpeg-cvslog] r15536 - trunk/libavformat/mov.c

[Michael Niedermayer]

On Fri, Oct 03, 2008 at 06:34:12PM -0700, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> > On Fri, Oct 03, 2008 at 09:37:42PM +0200, bcoudurier wrote:
> >> Author: bcoudurier
> >> Date: Fri Oct  3 21:37:41 2008
> >> New Revision: 15536
> >>
> >> Log:
> >> set sample rate for amr to allow stream copy since no decoder is present,
> >> 3gp does not store sample rate in stsd in fact. Fixes #674.
> >>
> >>
> >> Modified:
> >>    trunk/libavformat/mov.c
> >>
> >> Modified: trunk/libavformat/mov.c
> >> ==============================================================================
> >> --- trunk/libavformat/mov.c	(original)
> >> +++ trunk/libavformat/mov.c	Fri Oct  3 21:37:41 2008
> >> @@ -991,6 +991,9 @@ static int mov_read_stsd(MOVContext *c, 
> >>      case CODEC_ID_AMR_WB:
> >>          st->codec->frame_size= sc->samples_per_frame;
> >>          st->codec->channels= 1; /* really needed */
> >> +        /* force sample rate for amr, stsd in 3gp does not store sample rate */
> >> +        if (st->codec->codec_id != CODEC_ID_QCELP)
> >> +            st->codec->sample_rate = 8000;
> >>          break;
> > 
> > I was wondering if not maybe something like
> > if(!st->codec->sample_rate)
> >     st->codec->sample_rate = 8000;
> 
> This would only work if sample_rate is not set previously when reading
> stsd, I agree setting it is not correct in some cases, however, I fear
> indentifing 3gp in all cases will be complicated even with brands, and
> in most cases timescale/sample_rate is correctly set to sample rate like
> suggested in specs (but not mandatory).

IIRC the iso based file formats have default values for things,
thus things should IIRC either be set to te default or to the correct
value.
If iam correct then if(sample_rate != default) -> sample_rate is correct
and should not be overridden by 8khz
Of course i do not know if existing files follow the spec, also ive not
checked the spec iam just writing from memory ...


> 
> > or
> > if(3gp)
> >     st->codec->sample_rate = 8000;
> > would be cleaner ?
> 
> Humm aac in 3gp may not be 8000 :/

aac also wouldnt run the AMR/QCELP part of the switch() :)
but still i agree that identifying 3gp isnt easy :(


> 
> In the end, I was thinking that the code was this way since a long time,
> and definitely amrnb and amrwb only support mono 8000 hz, so I decided
> to go for this solution.

amrwb was 16khz before not 8khz ...

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

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-cvslog/attachments/20081004/37a55aeb/attachment.pgp>