AcoustIDs for 5.1 recordings and videos

Are 5.1 and music video recordings supposed to be linked to AcoustIDs at all?
And if so then are the AcoustIDs expected to be the same as those of the corresponding stereo recording?
Example: Track “12331f5e-02f2-4f88-bbae-02dcbc68a4ef” | AcoustID is currently linked to all 3 types of recordings.
BTW, this was asked but not answered before already: Are DTS AcoustIDs valid? - AcoustID - MetaBrainz Community Discourse

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The videos get AcoustIDs because people convert the videos to audio MP3\FLAC and then fingerprint them.

I agree with you that this is just weird and wrong. Videos should not have AcoustIDs.

(Back shortly… about to do a test on some multi-channel FLACs…)

I have some multi-channel FLACs - 5.1 and 4.0 files of the same album. And you can create finger prints with them in Picard, which convert to AcoustIDs no problem. These AcoustIDs are different for each mix, but these mixes also have different engineers involved.

Okay… more testing. And Picard happily generates AcoustIDs for mkv videos files too now. Clever thing it is.

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Thanks a lot for checking this with your files.
Were you referring to remixes when you said that the AcoustIDs are different for each mix? Or did you mean that the stereo and 5.1 mix of the same song typically have different AcoustIDs?
E.g. Depeche Mode – Ultra (2007, SACD) - Discogs has additional 5.1 mix engineer ARs for the multichannel section so these tracks may be considered (re)mixes of the original stereo album tracks.

The examples I had to hand were 5.1 and quad mixes of Wish You Were Here. These were produced by different engineers many decades apart. So even if they are the same source, the different engineers will have mastered the audio in different ways. And no doubt put the audio into different speakers.

I doubt a 5.1 mix would give the same fingerprint as a stereo version. I don’t know how the maths work of AcoustID. It may only listen to two channels, or may spread maths over all six, but it would unlikely be a formula that can compare to a stereo result.

As to “are these different mixes”, yes. In MB eyes, when you change the channel count these are separate recordings. 5.1 is separate to quad is separate to stereo and mono.

And if someone take that quad recording and remasters it to two channel stereo for a CD, it is another recording again. I put money on each of these versions giving you a different AcoustID.

Meanwhile in the messy world of AcoustID data, there are plenty of example where people have mixed up these recordings like in the example of your original post. But also notice that is 1392 for Stereo, 6 for 5.1, and 1 for the video. Pretty certain that tells you this is only a Stereo AcoustID and the other two should not be there and can be safely disabled

Again on your original example, click on the link to Barrel of a Gun (5.1) and you’ll see that recording has three AcoustIDs attached. Look at each one and read the list below the numbers. Interesting that only one of these three examples mentions [6ch]

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chromaprint simply downmixes all multichannel audio to one by computing the average (mean) of the sample values across all channels, and then proceeds with the resulting single waveform to calculate the fingerprint.

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That was my assumption as well. So if the 5.1 mix was basically just a redistribution of the original audio across the channels it should create an AcoustID very similar to the one of the stereo mix.

Looking into the example that Ivan derived from my original one confirms that:

2 of the 3 AcoustIDs attached to Barrel of a Gun (5.1) seem to correspond to the stereo mix and match perfectly: Compare fingerprints #43444454 and #11779191 | AcoustID

The 3rd one appears to be the real one according to the metadata. It is very similar to the others but does not match perfectly: Compare fingerprints #30480816 and #11779191 | AcoustID (offset -14)

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Still not sure about videos, though.
If “Picard happily generates AcoustIDs for mkv videos files” and the audio is the same as in the stereo recording (which is very often the case) then as I understand it it’s correct to have the same AcoustID linked to both recordings.

The 5.1 would look similar, but would be a different value. Very unlikely to come out the same.

I don’t know the video in the example. So can’t really comment. Sometimes videos have slightly different intros than the album or single.