How come lossless varies in compression?
Dec 28, 2006 at 8:19 PM Thread Starter

trose49

Banned
I noticed that songs can range from lets say 500-over 1,000aac depending on the disk?

What determines the compression rate?

Dec 28, 2006 at 8:22 PM
Because some tracks are easier to compress due to smaller amounts of data in the WAV file to reduce. Its the same thing with .rar or .zip. Both are lossless compression formats, but the size can different.

Compression rate depends on what you're compressing, how much you're compressing it, and how fast your PC is.

Dec 28, 2006 at 8:25 PM
Quote:

 Originally Posted by jmmtn4aj /img/forum/go_quote.gif Because some tracks are easier to compress due to smaller amounts of data in the WAV file to reduce. Its the same thing with .rar or .zip. Both are lossless compression formats, but the size can different. Compression rate depends on what you're compressing, how much you're compressing it, and how fast your PC is.

Does that mean if the file is more compressed than the quality of the original is not as good a another file that does not compress as much?

Dec 28, 2006 at 8:38 PM
Quote:

 Originally Posted by trose49 /img/forum/go_quote.gif Does that mean if the file is more compressed than the quality of the original is not as good a another file that does not compress as much?

No.

The quality is exactly the same, it isn't losing anything, that is why it is labeled as lossless.

How a zip file or a lossless audio file works is that it looks for patterns of 1's and 0's. For instance, it could change 100001000 (CD quality WAV file) to something like 101100 (compressed lossless file) with an algorithm. The CPU's job is turning the 101100 back into 100001000 when the audio file is played. So, once the file is uncompressed for the brief moment it is played, the quality is exactly the same as its original source.

Basically, if the algorithm is complex, it can get the size down to something smaller than other, simpler algorithms. The only difference here is that the smaller lossless files use a more complex algorithm to get them down to that size. Therefore, it's going to take more CPU processing power to uncompress the sound before it can be played. The sound quality is no different between the two.

So, if size isn't an issue on an MP3 player, it's best to have lossless files with less compression, so your MP3 battery life lasts longer. Higher compression lossless files will make your MP3 player use more juice trying to uncompress the songs, and use more CPU power. On a computer, usually people go with the highest compression because a computer can easily uncompress the files.

I hope that explains everything.

Dec 28, 2006 at 8:40 PM
Quote:

 Originally Posted by trose49 /img/forum/go_quote.gif Does that mean if the file is more compressed than the quality of the original is not as good a another file that does not compress as much?

No such correlation exists. For instance one could try to losslessly compress white noise and it won't compress at all

Dec 28, 2006 at 8:47 PM
Quote:

 Originally Posted by danmagicman7 /img/forum/go_quote.gif No. The quality is exactly the same, it isn't losing anything, that is why it is labeled as lossless. How a zip file or a lossless audio file works is that it looks for patterns of 1's and 0's. For instance, it could change 100001000 (CD quality WAV file) to something like 101100 (compressed lossless file) with an algorithm. The CPU's job is turning the 101100 back into 100001000 when the audio file is played. So, once the file is uncompressed for the brief moment it is played, the quality is exactly the same as its original source. Basically, if the algorithm is complex, it can get the size down to something smaller than other, simpler algorithms. The only difference here is that the smaller lossless files use a more complex algorithm to get them down to that size. Therefore, it's going to take more CPU processing power to uncompress the sound before it can be played. The sound quality is no different between the two. So, if size isn't an issue on an MP3 player, it's best to have lossless files with less compression, so your MP3 battery life lasts longer. Higher compression lossless files will make your MP3 player use more juice trying to uncompress the songs, and use more CPU power. On a computer, usually people go with the highest compression because a computer can easily uncompress the files. I hope that explains everything.

Great explanation. I was actually wondering the same thing as the OP, but you clarified everything.

Dec 28, 2006 at 8:53 PM
Quote:

 Originally Posted by M0T0XGUY /img/forum/go_quote.gif Great explanation. I was actually wondering the same thing as the OP, but you clarified everything!

Thanks!

After I read it...I was like, wow, that really makes sense. I didn't expect that outcome.

Dec 28, 2006 at 9:31 PM
Quote:

 Originally Posted by trose49 /img/forum/go_quote.gif Does that mean if the file is more compressed than the quality of the original is not as good a another file that does not compress as much?

No nothing to do with quality of the original. For example classical music and acoustic compresses very well compared to metal. However classical and acoustic often benefit more from lossless since they contain more spacial cues.

Dec 28, 2006 at 10:10 PM
But isn't there also the issue of more battery life being wasted reading a less compressed file?

Dec 28, 2006 at 10:32 PM
Quote:

 So, if size isn't an issue on an MP3 player, it's best to have lossless files with less compression, so your MP3 battery life lasts longer. Higher compression lossless files will make your MP3 player use more juice trying to uncompress the songs, and use more CPU power.

No, small differences in CPU power drain are not the major factor determining battery life on a hard drive-based player (and I assume we're talking about a hard drive player if file size isn't an issue), disk drive access is. In a hard drive player chunks of program material are retrieved from the drive and stored in buffer RAM, and then the drive is turned off for a while to save power. The less compressed the tracks are the more the drive will have to run to keep the buffer filled, and the more battery power will be used. In most players smaller file sizes (more compression) will result in better battery life and lossless files with less compression will do just the opposite.