[M4IF Technotes] Number of Channels

[emre.aksu nokia.com]

Hi,
> > You can get it from Decoder_specific_info presented in 
> > ES_Descriptor
> > of partricular audio track.
> I don't think this is mandatorily present in 3GPP branded files.

For 3GP files containing MPEG-4 Audio media track, the Decoder Specific Information is always present in the ESD Box of this particular track's AudioSampleEntry Box and the number of channels can be extracted from this location. 
For 3GP files having AMR Narrow Band or AMR Wide Band, Olivier is correct. There is no ESD Box present. The reason is simple. AMR-NB and AMR-WB audio media track is always mono and one-channel, hence no need to signal channel information.
BR,
Emre
Emre Baris Aksu
Nokia Mobile Phones
Tieteenkatu 1
FIN-33720
Tampere-FINLAND
> -----Original Message-----
> From: ext AVARO Olivier FTRD/DIH/REN
> [mailto:olivier.avaro   rd.francetelecom.com]
> Sent: 05 December, 2002 12:23
> To: A V S Y Naidu; Mahendran, Shanmuga Sundaram
> Cc: technotes   lists.m4if.org
> Subject: RE: [M4IF Technotes] Number of Channels
> 
> 
> 
> > You can get it from Decoder_specific_info presented in 
> > ES_Descriptor
> > of partricular audio track.
> I don't think this is mandatorily present in 3GPP branded files.
> Maybe another good reason to multi-brand your files and have MP4
> branding as the common denominator so that we avoid YAMM (yet another
> multimedia mess).
> 
> Kind regards,
> Olivier
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