[Mp4-tech] Re: Number of channels in HE-AAC audio elementary stream

[Ralph Sperschneider]

Ð쾧Ã÷ wrote:
> Yes. Please also note that the sum is the number of channels in that program. There can be up to 16 independent program_config_elements in one frame. And program_config_elements must come before all other syntactic elements in a raw_data_block.
>   

Wait a minute: We need to distinguish here between MPEG-2 and MPEG-4.
Your statement counts only for MPEG-2. And in MPEG-2, there is also an
implicit channel mapping possible, where the channel configuration is
only known after parsing the whole first frame.
In MPEG-4, PCEs within the payload do not need to be evaluated (but only
need to be parsed). Though, in MPEG-4, only the PCE in the
AudioSpecificConfig is of interest (and there can be only one).
>  
> Date: Thu, 28 Feb 2024 14:42:23 +0530 (IST)
> From: Angshuman Chatterjee <xl3k yahoo.com>
> Subject: Re: [Mp4-tech] Number of channels in HE-AAC audio elementary
>         stream
> To: mp4-tech lists.mpegif.org
> Message-ID: <701635.18432.qm web94314.mail.in2.yahoo.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> Thanks for the response.
>
> Please note that I am not looking for the channel to speaker mapping, but only the number of channel in the audio.
>
> Just to confirm whether I have understood it correctly, do I have to add up the values of the following parameters mentioned in
> program_config_element function?
>
> num_front_channel_elements
> num_side_channel_elements
> num_back_channel_elements
> num_lfe_channel_elements
> num_assoc_data_elements
>   

Hmm, assoc_data does actually not count here.
> num_valid_cc_elements
>   

Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 6167
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