[Flac-dev] Why so many lossless formats?

[Jon Colverson]

First off, I'm not an expert in this field, but I thought I could
probably answer a few of your questions. If anyone else wants to give a
more complete explanation, please do.

Brian Willoughby wrote:
> Hi folks,
> 
> I'm trying to get a handle on the many lossless audio formats from 
> the perspective of a software developer. I love the FLAC format 
> because it is open source and it performs very well. But there is 
> also the MLP (Meridian Lossless Packing), AAC (Apple Lossless), and 
> probably some Microsoft format(s) that compete in the same feature 
> set. These formats all achieve approximately 2:1 compression without 
> loss of detail.

AAC is not the same thing as Apple Lossless. AAC is a lossy format and
one of the audio formats in the MPEG-4 specification. It is used by
iTunes and the iTunes Music Service. Apple Lossless is another format
that is also supported by iTunes.

> What I would like to know is where to go to find out the details on 
> these formats.  Is MLP documented anywhere?  It has been accepted as
>  an audio format for DVD-HD, so does that mean it must be openly 
> documented?

I don't know about DVD-HD, but MLP can also be used on DVD-Audio discs,
so presumably it's part of (or referenced by) that specification.

> Dolby Digital AC-3 is documented as part of the HDTV specification, 
> but it cannot be implemented without paying licensing.  Well, a 
> programmer could implement it based on the specification, but could 
> not make a product without licensing.

Dolby Digital, aka AC-3, aka A/52, is not a lossless format. It is used 
on DVD-Video discs. There is at least one open source implementation of it:

http://liba52.sourceforge.net/

You are correct about the licensing. Many other audio formats are also
encumbered by patents (MP3 and AAC, for example).

> Also, what about Apple's Lossless format?  Is this part of a larger 
> specification, like MPEG-4, or is it completely independent?  Is it
> documented anywhere?

I believe it's a proprietary Apple thing, and I don't think it's 
documented. I believe that iTunes stores Apple Lossless tracks in an 
MPEG-4 container, however.

-- 
Jon