Axiom Home Page Forums General Discussion Home Theater Dolby TrueHD and DTS Master HD question

I tend to refer to lossless compressed sound like a Zip file.

We are all pretty familiar with Zip files. It is a way to take some files and compress them into a smaller space by removing unnecessary bits. You can often take a file and make it half as big as it was before.

When you unzip the file, it appears exactly the same as it was before. Your email, your word document, your family pictures, come out exactly the same as they were before you zipped them. If it was a lossy compression, you would lose parts of your emails and your kid's pictures would be without their face.

Lossless compression works the same way as zipping a file. PCM audio has a lot of unnecessary information that just takes up space but doesn't do anything. It is a pretty bad way to pack in your information. It is like letting your wife pack the van before a trip. She is probably terrible at it and fits it all in the van improperly and wastes space. When you go back in and pack the van yourself, you find all sorts of ways to pack the van with more efficiency to get more stuff in a smaller space. When you get to your destination, you didn't have to leave the dog behind because you couldn't fit it in the van.

So, there is no technical way that a lossless PCM track can sound any different than a lossless TrueHD or DTS Master soundtrack. The dog still has his nose and your email still says the same dumb gossip that it started with.

That said, even lossy compression sounds great to me. In a blind test with friends, not one of us could determine reliably what was lossy vs lossless. Could we determine a difference? Sure we could. Each had a slightly different sound. Most apparent was that each had a different volume level. But we couldn't determine which one was the lossless vs which one was the lossy. I don't bother myself with it. I will listen to whatever is the default track. I will even rip some disks to a player that can't pass HD audio and it makes no difference to me whether it is lossless or lossy.

On a side note, some of you also talk about video. I think it should be made clear that video is always compressed. A non-compressed hour of video takes something like 2TB. That is Terra Bytes. That is one of the largest harddrives available for each hour of video. A BD is most often compressed using the h.264 compression scheme which as you can see, results in a fantastic picture. it is pretty hard to find compression artifacts in many of the compressed h.264 video streams available today.