[Mp4-tech] Re: [Audio] About AAC Audio Streaming

[Ralph Sperschneider]

Li Zhengming wrote:
> Dear all,
> 
> I'm testing streaming mp4 with aac audio now. I encode a two-channel wav file into
> an aac file with ADTS header. Then I try to listen to this aac file with some aac
> decoders, it's ok and both two channels are present. But when I create a mp4 file
> with this aac file using mp4creator60 of the MPEG4IP project, and stream it with
> Darwin Server, the player can only give me the left channel. I have tried many
> files with two channels, and the results are the same.

A two channel signal is usually coded using a channel_pair_element(). It is 
almost impossible to extract just one channel out of this 
channel_pair_element(), when manipulating the data only in the coded domain. 
Thus, the channel_pair_element() is most likely also in the second case present 
and is being decoded using the AAC decoder. It is most likely just not rendered. 
This might be due to wrong settings in the AudioSpecificInfo(), which needs to 
be created at the time of the conversion from adts to mp4ff.
Hope this helps,
Ralph
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Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
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