Multichannel AAC Conversion

[Darkshadow1948]

I have several files with 6.1 and 7.1 aac audio tracks and I'd like to know if there is anyway to convert them to Dolby Digital with the same number of channels. If this is not possible is there some way to downmix them to 5.1 ac3 without losing proper channel placement and information? I already know how to convert 5.1 aac to 5.1 ac3 so I can play them through my AV processor. The additional channels I do find a problem to convert without messing them up.

[sneaker]

Dolby Digital cannot do more than 5.1 channels. Try:
ffmpeg -i "input" -map 0 -c:v copy -c:a ac3 -ab 640k -c:s copy "output"

[Darkshadow1948]

Thanks for your quick reply. I was afraid ac3 had a 6 channel limit. I'm assuming there is professional software out there that can convert 6 and 7 channel aac to their Dolby counterparts, but I'm sure there's royalties to Dolby Labs involved.

[JVRaines]

sneaker just gave you an FFmpeg command to do it for free.

[pandy]

Thanks for your quick reply. I was afraid ac3 had a 6 channel limit. I'm assuming there is professional software out there that can convert 6 and 7 channel aac to their Dolby counterparts, but I'm sure there's royalties to Dolby Labs involved.

You may try to convert more than 5.1 to EAC3 - in theory it should support up to 13.1 https://en.wikipedia.org/wiki/Dolby_Digital_Plus
ffmpeg is equipped in EAC3 but i'm not sure how capable it is.