New Ultra Fast Lossless Audio Codec (HALAC)

Post by crtasm » Thu, Jan 04, 2024, 2:36 AM UTC

adastra22 wrote: post #170

CharlesW wrote: post #137

Earlier quoted context omitted.

> There just isn’t something better (and free) to replace it yet. Apple's ALAC (Apple Lossless Audio Codec) format is an open-source and patent-free alternative. I believe both ALAC and FLAC support up to 8 channels of audio, which allows them to support 5.1 and 7.1 surround. https://en.wikipedia.org/wiki/Apple_Lossless_Audio_Codec#His... These are distribution formats, so I'd be surprised if there were demand for fl…

When FLAC compresses stereo audio, it does a diff of the left and right channels and compresses that. This often results in a 2x additional compression ratio because the left and right channels are tightly correlated. Unless things have changed substantially and I missed it, FLAC does not do similar tricks for other multichannel audio modes. Meaning that for surround sound, each channel is independently compressed an…

Post by crtasm » Thu, Jan 04, 2024, 6:00 PM UTC

adastra22 wrote: post #192

crtasm wrote: post #191

Earlier quoted context omitted.

In what ways does flac suck for distribution? All the music I download from Bandcamp is in that format, it works great for me.

It could be much smaller, maybe 2-3x better compression. Better support for surround sound / multichannel audio. If an AAC stream were used for the lossy predictive stage, then existing hardware acceleration could be used for energy efficient playback.

Post by adastra22 » Fri, Jan 05, 2024, 11:57 AM UTC

crtasm wrote: post #193

adastra22 wrote: post #192

Earlier quoted context omitted.

It could be much smaller, maybe 2-3x better compression. Better support for surround sound / multichannel audio. If an AAC stream were used for the lossy predictive stage, then existing hardware acceleration could be used for energy efficient playback.

How would 2-3x better compression be achievable? I don't use or desire multichannel audio but that and the hardware acceleration are interesting points.

Post by crtasm » Fri, Jan 05, 2024, 7:53 PM UTC

adastra22 wrote: post #195

crtasm wrote: post #193

Earlier quoted context omitted.

How would 2-3x better compression be achievable? I don't use or desire multichannel audio but that and the hardware acceleration are interesting points.

FLAC uses 1970’s era compression technology for both compression stages (lossy and residual) in order to conservatively avoid patents in the implementation. Just replace the lossy component with AAC, which is now out of patent protection, and replace Rice coding for the residual with the much better (but was still patented in the 90’s) arithmetic coding. Those two changes should get 2-4x performance improvement, as w…

Post by shdh » Mon, Jan 08, 2024, 10:24 AM UTC

adastra22 wrote: post #189

shdh wrote: post #183

Earlier quoted context omitted.

> FLAC works by running a lossy compression pass, and then LZ encoding the residual. Since when does FLAC run a lossy pass? You can recover the original soundwave from a FLAC file, you can't do the same with an MP3. I'm pretty sure FLAC does not run a lossy compression pass. Flickering textures in game engines are likely due to z-fighting, unless you're referring to some other type of flickering. If you're looking to…

> The FLAC encoding algorithm consists of multiple stages. In the first stage, the input audio is split into blocks. If the audio contains multiple channels, each channel is encoded separately as a subblock. The encoder then tries to find a good mathematical approximation of the block, either by fitting a simple polynomial, or through general linear predictive coding. A description of the approximation, which is only…