I want to add multi-channel into my format selection config can, can I do that?

[mzso]

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Question

Hello!
I already have a convoluted format selection configuration, that I got with some help. Which prefers opus over Vorbis over AAC. (Also video with resolution preferred over format up to a certain size, otherwise vp9 preferred)
But recently I noticed that new higher bitrate multi-channel audio streams (formats 258, 256) were added which makes sense to be preferred, but apparently only in AAC. So I'd like to add them somehow.

-f "(bestvideo[vcodec=vp9]/bestvideo[vcodec^=avc]/bestvideo[vcodec!=vp8])[height<=1440]+(bestaudio[acodec=opus]/bestaudio[acodec=vorbis]/bestaudio[acodec^=m4a]/bestaudio)/(best[vcodec=vp9]/best[vcodec^=avc]/best[vcodec!=vp8])[height<=1440]"

Example video:
https://www.youtube.com/watch?v=_ttYSpt8oiw

Or should I just revert to bestaudio? I don't know if bestaudio actually selects bestaudio, or tries to combine AAC for AVC and opus/vorbis to VP9. Besed on the formats available for the example video it might work if bestaudio only looks at bitrate only. Though I'm not sure if there are videos with residual stereo AAC streams of higher bitrate than opus which I don't want. Or vorbis streams for which the bitrate I don't remember.

[dstftw]

https://github.com/ytdl-org/youtube-dl#format-selection

[mzso]

@dstftw commented on 2019. szept. 15. 12:35 CEST:

https://github.com/ytdl-org/youtube-dl#format-selection

Yeah, well it's a tad complicated. And it's difficult to test without videos that have every single format possible.

[mzso]

Doesn't format selection have channel number meta fields?
Otherwise I'm not sure what I want is possible in a generic way.

[mzso]

This attempted workaround doesn't seem to work at all:
-f "(bestvideo[vcodec=vp9]/bestvideo[vcodec^=avc]/bestvideo[vcodec!=vp8])[height<=1440]+(bestaudio[acodec=opus][abr>170]/bestaudio[acodec=vorbis][abr>170]/bestaudio[abr>170]/bestaudio[acodec=opus]/bestaudio[acodec=vorbis]/bestaudio/[acodec^=m4a]/bestaudio)/(best[vcodec=vp9]/best[vcodec^=avc]/best[vcodec!=vp8])[height<=1440]"

[remitamine]

the number of audio channels has to be introduced(documented) and extracted.

{
    'itag': 258,
    'url': '[URL]',
    'mimeType': 'audio/mp4; codecs="mp4a.40.2"',
    'bitrate': 386741,
    'initRange': {
        'start': '0',
        'end': '591'
    },
    'indexRange': {
        'start': '592',
        'end': '743'
    },
    'lastModified': '1540024145491026',
    'contentLength': '4485228',
    'quality': 'tiny',
    'projectionType': 'RECTANGULAR',
    'averageBitrate': 385333,
    'audioQuality': 'AUDIO_QUALITY_HIGH',
    'approxDurationMs': '93119',
    'audioSampleRate': '48000',
    'audioChannels': 6
}

[mzso]

@remitamine commented on 2019. szept. 23. 16:04 CEST:

the number of audio channels has to be introduced(documented) and extracted.

Cool. But I also can't figure out why my workaround with bitrate > 170 doesn't work.
Apart from the above I also tried:
-f "(bestvideo[vcodec=vp9]/bestvideo[vcodec^=avc]/bestvideo[vcodec!=vp8])[height<=1440]+((bestaudio[acodec=opus]/bestaudio[acodec=vorbis]/bestaudio)[abr>170]/bestaudio[acodec=opus]/bestaudio[acodec=vorbis]/bestaudio[acodec^=m4a]/bestaudio)/(best[vcodec=vp9]/best[vcodec^=avc]/best[vcodec!=vp8])[height<=1440]"

Either I'm missing something or something's bugged.