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ALAC 24 bit

  • 26 March 2019
  • 6 replies
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I bought a 24 bit ALAC track and Sonos does not want to play it. I found another thread that said the FLAC engine had been updated with 24 bit support. Maybe the ALAC engine could get a bump as well?
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Best answer by ratty 26 March 2019, 11:20

Supported formats are listed in this article. I agree that having Sonos skip files with incompatible bit depth or sampling rate during the library index scan would be useful. One can only assume it just reads the tags it requires to populate the index, rather than filtering based on other values.
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Sonos has no stated intention to support 24-bit officially. The fact that FLAC 24-bit is played -- apparently reduced to 16-bit -- is a side-effect of another change. You must downconvert your ALAC file to 16-bit yourself.
I don’t need 24bit output. ALAC and FLAC are not too different under the hood. But I suppose FLAC is a bit more mature
Maturity is not the issue. As I understand it the FLAC library was updated for internal reasons. The fact that 24-bit files can now be read (if not reproduced in full) was rather an accidental byproduct. It doesn't signal a change in strategy for Sonos so you shouldn't expect ALAC to follow suit.

That said, Sonos have stated in the past that they can see a bit of a case for 24-bit -- despite it being well known that 16-bit as a delivery format encompasses more than sufficient dynamic range for human hearing -- but not for the potentially damaging ultrasonics on offer from higher sampling rates.
[... 24bit FLAC decoding support] doesn't signal a change in strategy for Sonos so you shouldn't expect ALAC to follow suit. That said, Sonos have stated in the past that they can see a bit of a case for 24-bit [...]
Not sure what strategy would have to do with this. This isn't an audiophile-related question, it is a file that does not play on Sonos.

Furthermore, Sonos tries to play the file and claims it is not "correctly encrypted". Why not:
a) Have a blacklist of formats Sonos knows won't work
b) Scan the file header and dim/mark it as disabled in the UI (it is obviously scanning to detect metadata)

Of course, I would rather have it play.
Supported formats are listed in this article. I agree that having Sonos skip files with incompatible bit depth or sampling rate during the library index scan would be useful. One can only assume it just reads the tags it requires to populate the index, rather than filtering based on other values.
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You may be missing a key point here, Sonos uses open source software, stuff developed by other teams and individuals. If the folks that are working on FLAC, folks outside Sonos, made a decision to process more bits that has no impact on the possibly completely different folks, again outside Sonos, working on ALAC.

Why Sonos folks decided to update to the newer FLAC library, with the side effect of adding the new bits is something we will probably never know. Lower CPU usage, smaller code, bugs fixed or another reason could all be behind the switch.