[FFmpeg-devel] H264: mp4toannexb BSF and streaming

Tomas Härdin tomas.hardin
Wed Aug 18 16:18:51 CEST 2010

On Wed, 2010-08-18 at 16:06 +0200, Alexandre Ferrieux wrote:
> On 18/08/2010 15:33, Alexandre Ferrieux wrote:
> >
> > What I'm trying to do is understand where these "important" extradata
> > are in the 3GP chunk hierarchy:
> >
> > - either they already in a separate chunk that is non-causal (comes at
> > the end of the stream), and I'm doomed.
> >
> Further experiments with varied clip durations, sadly show that the above holds :(
> Indeed, the produced .3gp files contain a few O(1) blocks (which deserve the name of 'header' or 'trailer'), but also 
> unfortunately *two* O(N) blocks: 'mdat' for main bitstream, 'moov' for extradata. There being more than one toplevel 
> chunk O(N) in size, with important data in both, wipes any hope of live streaming. Good job, whoever designed that :/
> -Alex

Isn't the extradata the same if the encoder uses the same settings? What
I'm getting at is that you could use a LUT of "supported" settings with
corresponding extradata, and inject a few bytes before the 3GP stream
starts telling which settings were used? I'm guessing you don't need a
valid 3GP stream anyway (since one is nigh impossible to create).

AFAIK the only way to stream any QuickTime format variant is when
remuxing them, or any other case where the size of each packet is known
in advance (hard CBR like DV for instance). Apart from qt-faststart of
course, but then you're not really streaming anyway.

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