-filter_complex "[0:a] ..." does not skip disabled tracks

[markshw2222]

IPhone 16 introduced spatial audio. They use multiple audio tracks to carry audio. One track is enabled the other is disabled. When specifying filter_complex "[0:a]..." the first audio track is selected, even it is disabled

Apple spec: ​https://developer.apple.com/documentation/quicktime-file-format/preparing_sound_and_subtitle_alternate_groups_for_use_with_apple_devices/

In this case, the disable track also have no audio codec set, so conversion fails

./ffmpeg -y -i ~/Downloads/spatial_audio_test_swapped_short.MOV -map 0:v -c:v copy -filter_complex "[0:a] asetpts=PTS-STARTPTS [output_audio]" -map '[output_audio]' -c:a aac ~/multiaudio.mp4

[aist#0:1/none @ 0x122609b40] Decoding requested, but no decoder found for: none

[markshw2222]

note: if I'm explicit in track selection
-filter_complex "[0:a:1] asetpts=PTS-STARTPTS [output_audio]" - will work as I select good track

-filter_complex "[0:a:0] asetpts=PTS-STARTPTS [output_audio]" - will fail as I select disabled track (with no codec info)

[MasterQuestionable]

#11223