Article recommendation: ffmpeg AC4 support

[williamthrilliam]

3+ years ago someone requested ffmpeg support for the now launched ATSC 3.0 broadcast audio standard AC4. Patches have been offered but not merged. What’s the deal/status of support for this audio format in linux? I want to record and watch FIFA in 4K 😂!

[hajj_3]

Dolby AC-4 is covered by patents; most technologies related to it are proprietary.
In light of that, currently much better alternatives to Dolby AC4 are: Opus, AC3 and mp3. You can use any of those to watch FIFA in 4K.
Opus, AC3 and mp3 are currently widely supported in the audio equipment, software and codecs, with many high-quality FOSS implemetations.

Therefore, Dolby AC4 is of no particular interest in the next 10 years; such an insignificant and patent-encumbered technology probably doesn't warrant an article.

Nope. None of those other codecs are better alternatives. AC-4 offers excellent quality/compression. Dolby AC-4 is of interest as many tv broadcast standards are adopting it therefore we need a decoder in ffmpeg to decode it, patents are irrelevant in regards to it being included in ffmpeg.

[hajj_3]

True, AC-4 offers excellent quality/compression. However, when paired with a 4K video stream, the relative difference in stream bandwidth is negligible. You should simply use AC-3 instead of AC-4.
AC-4 is covered by patents. It is questionable whether a decoder can legally be distibuted as FOSS software.
I don't understand why would a TV broadcast standard be important for desktop computers. TV broadcast standards are for TVs.

1. ffmpeg isn't just used on computers, it is often used in standalone devices.
2. ac-4 is included in dolby atmos, some streaming services support atmos and therefore ac-4. I expect streaming services will use AC-4 instead of dolby digital plus on devices that support it.
3. If i record a broadcast on my computer that uses AC4 or using a satellite box running enigma linux distro i want to be able to have audio to play on my computer. Enigma boxes would be able to decode ac4 audio which they currently cannot.

[hajj_3]

1. standalone devices are made by corporations and they cost money; they can afford to license Dolby AC-4
3. You can't record a broadcast on your computer, because your computer is not a TV. If you want to record a TV broadcast, you must inevitably use a TV receiver. The TV receiver can easily feature a transcoder from video+AC4 into video+PCM or into video+AC3. On your computer, you can transcode video+PCM into whatever you want.

1. Cheap chinese boxes aren't going to licence AC-4. Also not all countries recognise software patents.
3. https://www.geniatech.com/product/a683/ - pc tuner. The files recorded from this cannot playback the audio using vlc/mpc-be etc. Hence why ffmpeg support is important.

[tildearrow]

Nope. None of those other codecs are better alternatives. AC-4 offers excellent quality/compression. Dolby AC-4 is of interest as many tv broadcast standards are adopting it therefore we need a decoder in ffmpeg to decode it, patents are irrelevant in regards to it being included in ffmpeg.

An audio format better than Opus?! I refuse to believe it.

[Quackdoc]

the only issue is that the AC-4 decoder was bad. and no one has stepped up to get it ready for inclusion

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