[FFmpeg-devel] [PATCH] DVB LATM parser

[Paul Kendall]

Micheal,
Sorry for the long delay in this! Been really busy with other things.
Now there is a bit of noise on the MythTV lists about this so I thought it
time that I get back to it.

On Thursday 18 September 2008 06:24:48 Michael Niedermayer wrote:
> Hi
>
> On Wed, Sep 17, 2008 at 04:57:46PM +1200, Paul Kendall wrote:
> > On Wednesday 17 September 2008 12:51:18 Michael Niedermayer wrote:
> > > On Fri, Jul 04, 2008 at 09:28:37AM +1200, Paul Kendall wrote:
> > > > On Thursday 03 July 2008 22:16:56 Paul Kendall wrote:
> > > > > Hi attached is a patch that provides a AAC LATM parser
> > > > > CODEC_ID_AAC_LATM I have been working on. The libfaad decoder is
> > > > > also patched to provide another codec the decoding for this codec
> > > > > id. There are minor patches to mpeg.c & mpegts.c to send stream id
> > > > > 0x11 to this codec id.
> > > > >
> > > > > With this patch I can get audio working perfectly for NZ DVB-T
> > > > > using the stock unpatched libfaad2 library.
> > > > >
> > > > > I would welcome comments and suggestions so this can be included in
> > > > > the ffmpeg codebase.
> > > > >
> > > > > Cheers,
> > > > > Paul Kendall
> > > >
> > > > Doh!
> > > > I missed a vital part of the patch! Putting the codec in the
> > > > allcodecs.c file! Heres a modified patch.
> > >
> > > I think a parser is not the correct place to remove the LATM stuff. A
> > > parser should only split things into frames and extract information,
> > > not remove information.
> > > This for example is important if one wants to preserve the LATM and mux
> > > it into another container.
> > > LATM could be removed in a bitstream filter ....
> >
> > Ok, I can look into this. Is there any docs on this.
>
> well ... the source code :)
> but you can ask questions here if you have any, also keep in mind if the
> bitstream filter API has any problems it could be changed ...
>
> Also note that a LATM parser or some changes to the AAC parser might still
> be required even with a bitstream filter, otherwise the AAC parser will
> likely be confused by the LATM stuff ...
>
The parser needs to be modified to handle the LATM wrapping and packetize the
stream. Should the parser also set the extradata so the decoder can use that
to set the channels, sample rate & sample size? or should this be left to the
bitstream filter?

The bitstream filter should just check the LATM wrapping and remove if present.

The decoder then gets raw AAC data and all the parameters have been set by the 
parser and so it should all work fine.

Is that the plan?

Paul