How to prefer .opus over .m4a?

[whoizit]

The Seal app on Android downloads .opus by default. According to the internet, this is an open format, unlike AAC in .m4a, which has better sound quality at the same bitrate. But for some reason, Flow prefers downloading .m4a. So, how to prefer .opus over .m4a? I can't find this in options

[zuhairhalawa]

There is no setting for this at the moment. Downloads are AAC in MP4 only (.m4a for audio, .mp4 for video), and the code says this is intentional.

In the source (main):

• DownloadStreamPolicy.buildDownloadAudioFormats keeps only AAC formats ("every download is an MP4 or M4A"), so Opus never appears as a download choice.
• DownloadStreamPolicy.pickAacAudio states why Opus is skipped: Opus inside MP4 loses its first ~300 ms in Media3 (MP4 Opus: dOps PreSkip is read little-endian, so the first ~299 ms of audio are dropped androidx/media#3431).
• The only audio download preference is the song quality (Auto/High/Medium/Low), which selects an AAC bitrate, not a codec. The download codec option (Auto/H.264/VP9/AV1) applies to video only.

The v3.0.0 release notes also describe downloads as "M4A or MP4".

If you need .opus files, a feature request with that use case is the way to ask for it: https://github.com/Flow-Tube/Flow/issues/new/choose

[zuhairhalawa]

If this answers your question about .opus versus .m4a, could you mark it as the answer? It will help others looking for the same setting.