FLAC Joins The Xiph Family

Ancipital writes "Xiph.org (of Ogg Vorbis fame) have today announced that the FLAC (Free Lossless Audio Codec) project has joined the Xiph rebel alliance. The full story and press release can be found at the Xiph site. (FLAC is nice, because it gives you pristine lossless audio at roughtly 50% size reduction over uncompressed WAVs- you can store them on your hard drive/wherever and then transcode down to a lossy format when you need portability, yum!)"

Comments

Missing the Point

[dewboy]

I think many posters are missing the point of the article. My first reaction was also "hey, this is nothing new -- SHN (Shorten) has been around for a long time and does lossless encoding at 50% the size of WAV"... but then I actually went to the Xiph site and read their mission:

"Xiph.Org Foundation is a non-profit corporation dedicated to protecting the foundations of Internet multimedia from control by private interests. Our purpose is to support and develop free, open protocols and software to serve the public, developer and business markets."

So the point isn't that FLAC is new... the point is that FLAC is OSS, and has joined forces with an organization backing such efforts. The SHN codec is not OSS.

Very very cool

[Phexro]

I just started archiving my CD collection (350+ discs) using FLAC. I tested a number of codecs, including LAME, Ogg Vorbis, and FLAC.

In the end, I settled on FLAC for four reasons:

* It's completely lossless.
* Gapless playback
* If you save the TOC from the source CD, you can burn an exact copy, pregaps and all, from your FLACs.
* I can reencode to Ogg, MP3 or whatever lossy format I want at any time. Nice for when I want to make a MP3 disc to play on my MP3 walkman, and I don't lose quality like I would if my source material was in Ogg.

Hopefully, we'll see wider support for FLAC come from this partnership. Not too many players support FLAC, though the FLAC developers have made plugins for XMMS and WinAmp.

Oh, and some people have been tossing the '50% compression' thing around already. It really depends on the music. I have managed up to 70% compression on some sparse music, (mainly ambient and classical) while my death metal and noise encoded around 30%. It seems that the more dense the source is, the less it compresses.

Re:New?

[tuffy]

I don't see why FLAC is so cool, there has been lossless Audio Compression for some time now, in the form of Monkeys Audio Codec or MAC, it's been around for at least 2 years now

Near as I can tell, Monkey's Audio still doesn't work anywhere but on Windows (though support for other platforms is promised). FLAC works on Windows, MacOS9/X, Linux, BSD and even has hardware support. That single platform limitation makes Monkey's Audio difficult to justify for any serious audio preservation.

Re:huh?

[Inf0phreak]

The FLAC format has metadata support, and since you now can put FLAC in Ogg containers, it can also use Ogg tag support which is truly great.

In short: id3 (especially id3v2) sucks and should just DIE as soon as possible. Foobar 2000 even goes as far as to completely forgo id3v2 support on ideological reasons. Honestly, I think they are on to something.

Re:Algorithms?

[pclminion]

So what sort of compression algorithm does FLAC use?

For the most part, linear prediction. This uses a linear combination of past sample values to predict the next sample value. The difference between the prediction and the actual is Golomb-Rice encoded. Golomb-Rice codes are used when the probability of an integer occurring is geometric (i.e., the value N+1 is 1/R times as likely as the value N, for some R > 1). This is a pretty good assumption for audio, since the predicted values tend to be quite close to the real ones. Some other lossy compression algorithms also use linear prediction, but they quantize the predicted values to reduce the bitrate even further. The quantization is the lossy step.

MP3 and OGG, on the other hand, work differently. They first transform a block of audio using the MDCT, and apply a psychoacoustic model to the resulting spectral envelope. This eliminates a lot of subbands that are "inaudible." At that point the remaining subband energies are quantized and entropy-coded. To decode, the encoded energies are decoded and the spectral envelope is reconstructed, then transformed back into the time domain to become "audio" again.

It would be a serious feat to integrate FLAC and OGG. They are totally different systems.

Re:Is this REALLY a solution?

[kekoap]

Visit etree.org. The big benefit of lossless compression is it makes for better distribution of live recordings. The short of it is that demanding recordings in a losslessly compressed audio format, along with verification using checksum files, guarantees no loss in fidelity.

There are many alternate live-music trading scenarios which cause a loss in fidelity. Two of the most common: 1) CD Audio->CD Audio copies are not perfect (unless you use a specialized tool like EAC - Exact Audio Copy); 2) trading lossily-compressed audio tends to lead to loss of fidelity through inevitable decompression, writing to CD, reripping, and reencoding.

Re:Algorithms?

[Josh Coalson]

So what sort of compression algorithm does FLAC use?

• interchannel decorrelation: mid-side coding
• intrachannel decorrelation: FIR linear prediction
• entropy coding: Rice codes with a simple context mechanism

For more info see here

One idea that would be really cool is if they could get acheive lossless compression by noting the differences between the original and the .OGG, and appending that to the .OGG. Then if you can just strip off the added info when you make copies to restricted-space devices. The only question is whether this can be done with a competitive compression ratio.

This has been suggested before, but would require all Vorbis decoders to decode to the exact same result, which is not practical (Vorbis decodes to float samples).