Is there data loss when converting WAV to AIFF

[mb225]

I'm cleaning up my iTunes digital music server, getting everything tagged correctly and putting in missing album artwork, etc. When I originally ripped CDs I was ripping them as WAV but switched to AIFF format in iTunes about 1 year ago. So 70% of my music is stored as WAV and 30% as AIFF. The latest version of iTunes does not allow me to add artwork to WAV files. This did work in the past, I think Apple is starting to force their formats in iTunes (but this is another discussion). If I convert the WAV files to AIFF, it allows me to add my artwork. So the question is, if I use iTunes to convert my files from WAV to AIFF, will I introduce any data loss?

As a test I converted a WAV file to AIFF and then converted the AIFF file back to WAV and ran a "diff" on the two WAV files. The files were identical with a diff command. To me this tells me the WAV to AIFF conversion is bit-perfect.

To verify the test I used iTunes to convert a WAV file to MP3 (256 kpbs) and then converted the MP3 back to WAV and ran the diff on the WAV files. This file diff showed tons of differences.

As far as I can tell this proves converting WAV to AIFF in iTunes should preserve the original quality. But maybe I missing something? Any help would be greatly appreciated!

Thanks!

[chrispy35]

Your diff method is solid. There's no loss of data in converting from WAV to AIFF.

Chris P.

[littlesaint]

AIFF and WAV are essentially just wrappers or container formats for the raw, uncompressed LPCM audio bitstream. Converting from one to the other is just a matter of changing the wrapper, more or less. The audio bitstream is left untouched though, so yes, it should be the unaltered.

[bigburner]

AIFF and WAV are essentially just wrappers or container formats for the raw, uncompressed LPCM audio bitstream. Converting from one to the other is just a matter of changing the wrapper, more or less. The audio bitstream is left untouched though, so yes, it should be the unaltered.

Correct. Using AIFF is like using WinZip on a Word document. Are there any letters missing from your masterpiece when you zip and unzip the document? No. It just reduces the size of the file without eliminating any information.

Nigel.

[mb225]

Thanks all!! A really appreciate the information.

[mb225]

I performed a very interesting test today. BigBurner's comment about the Apple Lossless format made me wonder. If you convert something to lossless and then convert it back will it be the same? So I converted a WAV file to Apple Lossless and then converted the Apple Lossless file back to a WAV. I ran a diff on the 2 WAV files and they are NOT identical!!! 8O The files are 99% the same but the conversion introduced differences.

WTF? If Apple Lossless is just that, "Lossless" shouldn't the conversion create an identical file?

[wettou]

I performed a very interesting test today. BigBurner's comment about the Apple Lossless format made me wonder. If you convert something to lossless and then convert it back will it be the same? So I converted a WAV file to Apple Lossless and then converted the Apple Lossless file back to a WAV. I ran a diff on the 2 WAV files and they are NOT identical!!! 8O The files are 99% the same but the conversion introduced differences.

WTF? If Apple Lossless is just that, "Lossless" shouldn't the conversion create an identical file?

Hum :E

[stuofsci02]

This is news to me...

They should be the same... Most of my collection is in Apple Lossless...

I hate apple.. Should have gone FLAC..

[littlesaint]

I performed a very interesting test today. BigBurner's comment about the Apple Lossless format made me wonder. If you convert something to lossless and then convert it back will it be the same? So I converted a WAV file to Apple Lossless and then converted the Apple Lossless file back to a WAV. I ran a diff on the 2 WAV files and they are NOT identical!!! 8O The files are 99% the same but the conversion introduced differences.

WTF? If Apple Lossless is just that, "Lossless" shouldn't the conversion create an identical file?

Are you comparing files, or audio bitstreams? There's a difference.

[stuofsci02]

Are you comparing files, or audio bitstreams? There's a difference.

I think he is converting one format to the other and then back again. Then comparing the original to the twice converted file. I think by definition you should end up with two identical files..

[littlesaint]

I think he is converting one format to the other and then back again. Then comparing the original to the twice converted file. I think by definition you should end up with two identical files..

No you don't. Lossless codecs like ALAC and FLAC compress the original audio bitstream, not the original file. So doing a file diff is not a valid comparison. You have to compare the audio bitstreams in the container files. Best way is to use the Bit Compare component of foobar2000. In my own tests both FLAC and ALAC produce the same results with identical bitstreams, and maybe a few (<1000) empty samples added to the beginning or end of the track.

[stuofsci02]

No you don't. Lossless codecs like ALAC and FLAC compress the original audio bitstream, not the original file. So doing a file diff is not a valid comparison. You have to compare the audio bitstreams in the container files. Best way is to use the Bit Compare component of foobar2000. In my own tests both FLAC and ALAC produce the same results with identical bitstreams, and maybe a few (<1000) empty samples added to the beginning or end of the track.

Ahh... So you are saying the container file may differ each time even if you run the same encoder on the same original?

[littlesaint]

Ahh... So you are saying the container file may differ each time even if you run the same encoder on the same original?

It depends on the codecs and the software, but yes, the files may be different, but the audio data should always stay the same as you convert from codec to codec, as long as you stay in the lossless domain.