basmac;237999 Wrote: > The test file was > Dark Side Of The Moon/Speak To Me.aiff size 12058648 bytes > either on both CD readers or copied to disk. > So both files are the same length (in minutes & seconds). Looking at the size of an uncompressed aiff file tells you precisely nothing about the actual audio, it only tells you how long it is. One of those files could be complete garbage. It's like getting two boxes in the mail and assuming that because they're the same size they must have the same things inside.
> > I encoded to ALAC using iTunes and the sizes from doing "ls -l" are > given in previous posts, using the same Mac and settings each time. > And that strongly suggests to me that the content of the original files were _not_ the same, because the ALAC compression ratio will vary depending on the actual content. Different content results in a different size compressed file. On the flip side, if the compressed sizes were identical that would suggest pretty strongly that the original data was also identical. > > Given that the encoding back to aif gives the same size for both CD > readers is encouraging to me, even though its not the original size. > Why? As I explained before, that only tells us both drives agree how long the track is. > > Coming from a computer background I would bet encoding a file should > return the same filesize 100% of the time : n bytes encoded equals m > bytes. > Let's say file A is exactly 10mb and we zip it, resulting in A.zip which is 5mb. Now we take file B (also 10mb) and zip it, resulting in B.zip. It's very unlikely that B.zip will also be exactly 5mb unless the data in A and B were the same to begin with. So if you're saying that encoding a specific aiff file will always produce the same size output, I'd agree. If you're saying that encoding any aiff file of a particular size will result in the same size output, that's wrong. > > If encoding is adding headers or whatever, that should be the same size > as well. > Yes, which is again why the difference in compressed file sizes indicates a problem. > > Why encoding different filesizes back to the same is more of a mystery > to me eg. if one zips a file then unzips it it is the same filesizes. > Do you mean you don't understand why the initial aiff file you ripped isn't the same size as the file you got from uncompressing the alac one? That's likely because the decompressor added different headers to the aiff file than the original ripper. -- radish ------------------------------------------------------------------------ radish's Profile: http://forums.slimdevices.com/member.php?userid=77 View this thread: http://forums.slimdevices.com/showthread.php?t=39564 _______________________________________________ ripping mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/ripping
