Feature Request: Multichannel AAC to AC3

[stephenreay]

Some source material comes with the multi-channel audio encoded as e.g. 6-channel AAC.

This is not particularly hard to convert back to AC3 using ffmpeg from the command line, but it's quite cumbersome to have to do this manually on such media.

Thanks!

[Mock1]

Why do you want it as AC3? I see files where there is a 6ch AAC audio track, without any 2ch fallback, and I use the AAC + Passthru now that it's been enabled in the newest release (used to do it manually by reimporting the track again to get both 2ch and 6ch).
Is AC3 better? Worth converting? I'm working on a PR to update how some audio tracks are handled, including the AAC 6ch scenario above. If converting to AC3 is the right/desired thing, I can incorporate it into my changes

[stephenreay]

Most home theatre equipment (including AppleTV) know how to handle ac3 surround sound - even if it's just to pass the stream off to the receiver to decode it.

I've not seen any that treats 6ch AAC as anything but stereo.

[Mock1]

Makes sense to me. I'll add this into the work I'm doing now. To take multi-channel AAC tracks, and convert them to AC3 by default. We should leave the other options available though.
Could you see someone wanting to control the default behavior? Like how we can chose to convert/keep/discard DTS?

[Mock1]

This is covered in #68

[derpyjoystick]

Why do you want it as AC3?

AC3 is the most universally supported audio codec and has been for decades. Every old amp, speaker, dac, and usb stick that holds some kind of media player recognizes and supports it. It is akin to mp3. Everything handles it. From little mp3 players from 1998 to an iPhone from 2025.

Here are the audio codecs supported by the latest Apple TV:

HE-AAC (V1), AAC (up to 320 Kbps), protected AAC (from iTunes Store), MP3 (up to 320 Kbps), MP3 VBR, Apple Lossless, FLAC, AIFF, and WAV; AC-3 (Dolby Digital 5.1), E-AC-3 (Dolby Digital Plus 7.1 surround sound), and Dolby Atmos.

As you can see, it cannot natively play DTS. Because licensing. Which is another huge bonus of AC3, the codec is free (unlike AAC and Armos, which are proprietary and require licensing).

https://en.wikipedia.org/wiki/Comparison_of_audio_coding_formats

While AC3 is limited when compared to some of the newer and more robust multi channel codecs, it’s still the gold standard for compatibility. And there is open debate on how many channels one truly needs. I’d say converting to AC3 would be a huge QOL improvement!