[Ffmpeg-devel] [PATCH] Add fact chunk to non-PCM wav
Thu Nov 9 15:49:22 CET 2006
On Thu, Nov 09, 2006 at 01:53:08PM +0100, Michel Bardiaux wrote:
> Michael Niedermayer wrote:
> >On Thu, Nov 09, 2006 at 11:36:13AM +0100, Michel Bardiaux wrote:
> >>Michael has reported that
> >>>>interresting, accoridng to microsofts excelent and unambigous
> >>>>(not kidding ...)
> >>>> Fact Chunk
> >>>>This chunk is required for all WAVE formats other than WAVE_FORMAT_PCM.
> >>>>It stores file
> >>>>dependent information about the contents of the WAVE data. It currently
> >>>>specifies the time length of the
> >>>>data in samples.
> >>>>so this must not be under CODEC_ID_MSGSM, also it must be a seperate
> >>>>as its not CODEC_ID_MSGSM specific
> >>I took this literally, hence CODEC_ID_PCM_ALAW and CODEC_ID_PCM_MULAW
> >>will get a fact chunk too.
> >now just take the largest pts minus the smallest pts of any packet stored
> >and convert that by using AVStream.time_base and AVCodecContext.sample_rate
> >to the number of samples and store that in the fact chunk
> Right, the patch does not make sense without the final update of the
> chunk, and with a *general* formula, not the one I had specialised for
> MSGSM. I'm rather rusty on the handling of timestamps, so this might
> take some time
in the write packet function
assert(avpacket->pts != AV_NOPTS_VALUE);
context->maxpts= FFMAX(context->maxpts, avpacket->pts);
context->minpts= FFMIN(context->minpts, avpacket->pts);
and in write_trailer
number_of_sample= av_rescale(context->maxpts - context->minpts, avctx->sample_rate * (int64_t)avstream->time_base.num, avstream->time_base.den);
untested of course but it should work approximately that way ...
> (and though I can read the lists from home, posting does
> not work).
> >then run the regression tests and send a patch which updates the checksums
> Not clear how to proceed here, do you mean a subsequent patch, or in the
in the fact chunk patch, sorry for being unclear
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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