[vlc-devel] [PATCH 1/2] avcodec: fix Ambisonics AAC order 1 streams

Adrien Maglo magsoft at videolan.org
Mon May 14 17:26:30 CEST 2018

On 14/05/2018 17:08, Francois Cartegnie wrote:
> Le 14/05/2018 à 16:55, Adrien Maglo a écrit :
>> Do not reorder the audio channels. Keep the avcodec order.
>> +            p_sys->b_extract = false;
>>           p_dec->fmt_out.audio.i_physical_channels = i_layout_dst;
>>       }
> I don't get it. We already ignore the avcodec order and force the
> expected ambisonic ordering.

My previous patch was wrong. We were forcing a wrong new order. We must 
preserve the order given by avcodec, which is different from VLC order.
For these streams, b_p_sys->b_extract is true while we should keep the 
buffer as they are.

> If avcodec now stopped reordering ambisonic it lacks version check

Avcodec has never detected and reordered Ambisonics channels. It has an 
output channel order which is different than the VLC one. The right 
things to do for AAC Ambisonics order 1 streams is to leave the buffers 

Best regards,


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