[gst-devel] _Re:__Re:_re：_Re:_how_to_use_qtdemux_to_demux_h264_stream_from_MP4?

[Edward Hervey]

Hi,

  The qtdemuxer will give you a "codec_data" buffer in the h264 caps.
That codec_data is the content of the QuickTime 'avcC' atom. Doing a
search on google for "avcC atom sps" will lead you to documents or
code describing the contents of that atom, which contains all the
information you  want.

   Edward

On 3/23/07, jp_liu <jp_liu at astrocom.cn> wrote:
>
>
> Edward Hervey, Hello
>
> Now I clearly understand if I get sps data , pps data and nal_unit_size, I
> can covert mp4 file to byte-stream format.
> I need to know how to get these informations from qtdemux.
>
> jp_liu, jp_liu at astrocom.cn
> 2007-03-23
>
> ----- Receiving the following content -----
> From: Edward Hervey
> Receiver: jp_liu
> Time: 2007-03-28, 16:43:17
> Subject:
> Re:_Re:_[gst-devel]_Re:_[gst-devel]re：_Re:_how_to_use_qtdemux_to_demux_h264_stream_from_MP4?
>
>
>
>
>
> Hi,
>
>   I forgot to mention that this patch doesn't solve your problem, but
> changes some behaviour in qtdemux. The real question was whether it
> broke the behaviour of your decoder or not, since with the existing
> h264 decoders it doesn't.
>
>   Hoping somebody more knowledgeable about h264 will help solve your
> problem,
>
>     Edward
>
> On 3/28/07, jp_liu <jp_liu at astrocom.cn> wrote:
> >
> >
> > Edward Hervey, Hello
> >
> > Thanks for your reply.
> > But I think you have misunderstood .
> > My problem is my decoder(buy from 3rd party) can not decode the frame
> > without sps,pps and nal unit(Bytestream). I must covert the frames to the
> > Byte-stream frames, such as add sps pps at first frame , add start code at
> > each nal unit.... so your patch can not solve my problem,but anyway,
> thanks.
> >
> > jp_liu, jp_liu at astrocom.cn
> > 2007-03-28
> >
> > ----- Receiving the following content -----
> > From: Edward Hervey
> > Receiver: jp_liu
> > Time: 2007-03-27, 17:18:32
> > Subject:
> >
> Re:_[gst-devel]_Re:_[gst-devel]re：_Re:_how_to_use_qtdemux_to_demux_h264_stream_from_MP4?
> >
> >
> >
> >
> >
> > Hi,
> >
> > Could you also try applying the following patch fixing qtdemux so
> > that it outputs h264 buffers with pts instead of dts. If you are
> > making a software decoder you shouldn't need the dts.
> > the patch and explanations are here :
> > http://bugzilla.gnome.org/show_bug.cgi?id=423283
> >
> > Edward
> >
> > On 3/26/07, jp_liu <jp_liu at astrocom.cn> wrote:
> > >
> > >
> > > zhangfei gao, Hello
> > >
> > > My h264 decoder support say that:
> > > I believe MP4 uses the NAL format (Need to confirm) and hence doesn't
> have
> > > the NAL Start codes. One needs to convert that to bytstream format
> because
> > > our decoders support only byte-stream format. Also one needs to do this
> > > while demuxing it from MP4 otherwise the information various slice
> > positions
> > > would be lost.
> > >
> > > So, How should I do?
> > >
> > > jp_liu, jp_liu at astrocom.cn
> > > 2007-03-26
> > >
> > > ----- Receiving the following content -----
> > > From: zhangfei gao
> > > Receiver: gstreamer-devel
> > > Time: 2007-03-22, 21:24:01
> > > Subject: [gst-devel]re： Re: how to use qtdemux to demux h264 stream from
> > > MP4?
> > >
> > >
> > >
> > >
> > >
> > >
> > > hi, jp_liu
> > >
> > > "h264.c" in ffmpeg has useful information of how to parse "codec_data"
> > which
> > > get set_caps.
> > > "codec_data" has all the nal_length, sps data and pps data.
> > >
> > > Thanks
> > > Jan Schmidt <thaytan at noraisin.net> 写道：
> > > jp_liu wrote:
> > > > Hello, gstreamer-devel
> > > >
> > > > How to use qtdemux to demux h264 stream from MP4?
> > > > The demuxed h264 stream looks have no startcodes before every NAL
> > > > Unit. So, Some key information ( such as: SPS PPS ....) is missed. It
> > > > caused my H264 decoder can not decode the frame which demuxed by
> qtdemux
> > .
> > > > How can I solve this problem?
> > > >
> > >
> > > I think the information your decoder is looking for is the stuff
> > > provided by the 'codec_data' in the caps. This is the header information
> > > that quicktime stores and provides separately from the actual data
> stream.
> > >
> > > Regards,
> > > Jan.
> > >
> > >
> >
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> >
> > --
> > Edward Hervey
> > Multimedia editing developer / Fluendo S.A.
> > http://www.pitivi.org/
> >
>
>
> --
> Edward Hervey
> Multimedia editing developer / Fluendo S.A.
> http://www.pitivi.org/
>


-- 
Edward Hervey
Multimedia editing developer / Fluendo S.A.
http://www.pitivi.org/