[Mp4-tech] Re: [Audio] Daul Mono Channel support in AAC-LD

[Ralph Sperschneider]

chitturi suresh babu wrote:
> Hi
>  
> Is Dual Mono channels is supported in MPEG4 AAC-LD codecs?
> The reference software which we have do not have this support, But we 
> planned to add the code to support this
> feature, but I want to know whether LATM\LOAS format has support to 
> indicate this feature?
>  
> Will there be any use-case for this feature for AAC-LD codecs? 
>  
>  
> thanks
> Suresh

Hi Suresh,
dual mono, i.e. having two mono channels multiplexed in one Audio 
bitstream being produced by one encoder instance, is a relict from 
MPEG-1/2. In MPEG-4 there is no need to have two independent mono 
channels in one Audio bitstream. Therefore, this is not supported by 
MPEG-4 ER AAC LD.
In MPEG-4, the envisioned method  to transmit two mono channels is to 
instantiate two mono AAC encoders, which produce two mono AAC 
bitstreams. Those two bitstreams can then easily be multiplexed e.g. 
using LATM, where they are treated as two programs.
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 6167
Fraunhofer IIS                  | Fax:   +49 9131 776 6099
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