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Apple Lossless Preserved Bit Depth

 
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aubreyapple



Joined: 01 Mar 2007
Posts: 10

PostPosted: Sun Jun 30, 2019 10:51 pm    Post subject: Apple Lossless Preserved Bit Depth Reply with quote

I cannot find an answer to this: When saving as Apple Lossless, I have the option of 16, 20, 24, or 32 bit preserved depth. My question is this is this bits per channel or total bits? The file size does not seem to be different if I save a file as 16 bit or 32 bit, at least for my 16bit per channel audio. Just wondering. I saw another related query from 2013 but saw no answer.

Oddly I just tested and regardless of whether I select 32 bit or 16 bit, the files size is identical. Furthermore, the program mediainfo (in MacPorts) reports the bit depth is 32 bits in both cases. Yet another is that when I go to settings, it always defaults to 32 bits. I am wondering if the setting is being ignored? (All if this under 'Save Selection As...') On the other hand, if I 'Split According to Markers...', it does not ignore the bit setting and mediainfo reports 16bit for 16 bits and 32 bits for 32 bits. However, the preference is not preserved here either. (This is for version 2.5.3).

Now in version 2.6 (an update from Martin, not the release), it is even stranger. Save Selection As... results in not a Lossless file but an AAC LC file in both 16 and 32 bit modes. (Yes, Apple Lossless was selected.) In Split According to Markers... it correctly does 16 or 32 bits but the preference is not preserved.

It is also interesting that the 32bit m4a is nearly 4x the size of the 16bit one. This COULD be an artifact of the codec.

I guess this has turned into more than a simple question!
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Martin Hairer
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Joined: 08 Nov 2006
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PostPosted: Mon Jul 01, 2019 6:38 am    Post subject: Apple Lossless Preserved Bit Depth Reply with quote

Quote:
I cannot find an answer to this: When saving as Apple Lossless, I have the option of 16, 20, 24, or 32 bit preserved depth. My question is this is this bits per channel or total bits? The file size does not seem to be different if I save a file as 16 bit or 32 bit, at least for my 16bit per channel audio. Just wondering. I saw another related query from 2013 but saw no answer.

This is bits per channel and it refers to the precision at which the format is guaranteed to reconstruct the original data exactly. The file size should be increasing with the bit depth (it certainly is for me on a few sample files) but it is not directly proportional to it. Regards,

Martin

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aubreyapple



Joined: 01 Mar 2007
Posts: 10

PostPosted: Mon Jul 01, 2019 3:59 pm    Post subject: Reply with quote

Thanks for the clarification on bit depth. It seems that since I am starting with 16bit AIFF or WAV, that is all I need. That said...

Martin, please see the rest of the original post. It appears that Amadeus Pro is not always doing what the menus say it is supposed to do. Please comment on those issues aa well.
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Martin Hairer
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PostPosted: Tue Jul 02, 2019 4:33 pm    Post subject: Apple Lossless Preserved Bit Depth Reply with quote

Quote:
Martin, please see the rest of the original post. It appears that Amadeus Pro is not always doing what the menus say it is supposed to do. Please comment on those issues aa well.

If the original data is 16 bit, then the amount of data required to represent it at any level of precision beyond this will be the same, and it is therefore expected that the file size would be the same, whatever preserved bit depth you select. Regards,

Martin

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aubreyapple



Joined: 01 Mar 2007
Posts: 10

PostPosted: Tue Jul 02, 2019 4:36 pm    Post subject: Reply with quote

I guess you are not seeing the point of the remainder of the post. I will open a new thread.
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