Why do ALAC and AIFF files have different bit rates? Aren't they both lossless formats?

[redbasso]

Here's what I did:

 

1. Rip a track from a CD using ALAC (Apple Lossless). Get a .m4a file
   
2. Rip the same track from the same CD using AIFF. Get a .aiff file.
   
3. Compare the bit rate of the two files (⌘ + I on iTunes or afinfo from the command line).
   

The AIFF's bit rate is higher than the ALAC's... Why? How can a losslessly compressed audio file have a smaller bitrate than its losslessy uncompressed counterpart?

[wgscott]

The same reason as it has a smaller size. There is no info in some of them thar bits.

 

You can prove this to yourself by converting both to wav and comparing their checksums.

[Skeptic]

Divide the file size by the time to get bit rate.

If you reduce the file size by using compression, the bit rate goes down.

Quality is unaffected.

 

Bit rate is not a good metric for quality unless you are comparing files that use the same lossy compression format. Even then, different encoders can produce different results.

[gmgraves]

Here's what I did:

 

1. Rip a track from a CD using ALAC (Apple Lossless). Get a .m4a file
   
2. Rip the same track from the same CD using AIFF. Get a .aiff file.
   
3. Compare the bit rate of the two files (⌘ + I on iTunes or afinfo from the command line).
   

The AIFF's bit rate is higher than the ALAC's... Why? How can a losslessly compressed audio file have a smaller bitrate than its losslessy uncompressed counterpart?

 

 

I think that you might be misunderstanding what's going on here, I think. The lower bit rate of ALAC simply means that it's a more efficient lossless compression algorithm than is AIFF.

[bdiament]

AIFF is not compressed.

 

(There is a compressed version, called AIFF-C.)

 

Best regards,

Barry

Soundkeeper Recordings

The Soundkeeper | Audio, Music, Recording, Playback

Barry Diament Audio

[gmgraves]

AIFF is not compressed.

 

(There is a compressed version, called AIFF-C.)

 

Best regards,

Barry

Soundkeeper Recordings

The Soundkeeper | Audio, Music, Recording, Playback

Barry Diament Audio

 

By Jove you are right! I didn't think about that! Something about not seeing the forest for the trees. I was so concentrating on the difference in file size, that I completely overlooked the fact that in one instance (ALAC) we're dealing with a compressed format and in the other (AIFF) we're dealing with an uncompressed format. I need to pay more attention to the details. Now, if the OP were talking about the difference in file size between a ALAC file and a FLAC file (if, indeed, one exists - and I don't personally know that), then my comments might have had some validity. Mea Culpa.

 

Thanks for pointing that out, Barry!

[Cebolla]

AIFF is not compressed.

 

(There is a compressed version, called AIFF-C.)

Not forgetting that OS X produces AIFF-C files which are uncompressed because it uses the sowt codec, ie AIFF-C/sowt.

[bdiament]

By Jove you are right! I didn't think about that! Something about not seeing the forest for the trees. I was so concentrating on the difference in file size, that I completely overlooked the fact that in one instance (ALAC) we're dealing with a compressed format and in the other (AIFF) we're dealing with an uncompressed format. I need to pay more attention to the details. Now, if the OP were talking about the difference in file size between a ALAC file and a FLAC file (if, indeed, one exists - and I don't personally know that), then my comments might have had some validity. Mea Culpa.

 

Thanks for pointing that out, Barry!

 

Hi George,

 

You're welcome.

It is my favorite file format, for recording, mixing, mastering and for my listening server.

 

Best regards,

Barry

Soundkeeper Recordings

The Soundkeeper | Audio, Music, Recording, Playback

Barry Diament Audio

[bdiament]

Not forgetting that OS X produces AIFF-C files which are uncompressed because it uses the sowt codec, ie AIFF-C/sowt.

 

Hi Cebolla,

 

That codec is just "twos" spelled backwards. It reverses the bit order but is otherwise the same.

OS X will run either one.

 

Still, it is a raw, uncompressed PCM format - the way I like it. ;-}

 

Best regards,

Barry

Soundkeeper Recordings

The Soundkeeper | Audio, Music, Recording, Playback

Barry Diament Audio