Web Audio + 8 channels + Mpeg Dash

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Phil Johnson

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Mar 15, 2021, 5:43:27 AM3/15/21
to Chromium HTML5
I am having difficulties being able to control 8 channel audio from an mp4 as I would like in Chrome. Currently I have 2, 4 and 6 channel working as expected.

As a starting point I had a complete mp4 video with 8 channels of audio. Creating a simple js test bed allows me to load the video and control each channel of the audio e.g. turn on/off each channel and patch to either left/right ear, using Web Audio by using an 8 channel splitter. This works.

I have 2 methods of generating dash material, each resulting in the same issue. The second way uses mp4dash from Bento4 using the original mp4 as above.

Both methods result in, I think, the audio source having 2 channels premixed i.e. If I listen to just the second split channel I hear both channels 2 + 4 combined; and 2 channels blank e.g. channel 4.

Chrome does show I am getting 8 channels

Selected FFmpegAudioDecoder for audio decoding, config: codec: aac, profile: unknown, bytes_per_channel: 2, channel_layout: 7.1, channels: 8, samples_per_second: 48000, sample_format: Signed 16-bit, bytes_per_frame: 16, seek_preroll: 0us, codec_delay: 0, has extra data: false, encryption scheme: Unencrypted, discard decoder delay: false

Detected midstream configuration change PTS:0 Sample Rate: 48000 vs 48000, ChannelLayout: 27 vs 14, Channels: 8 vs 8

Can anyone further my investigations ?

Many thanks

Phil Johnson

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Mar 22, 2021, 1:40:36 PM3/22/21
to Chromium HTML5, Phil Johnson
Seems to be fixed in 91 ....
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