TSAC: Very Low Bitrate Audio Compression

TSAC is an audio compression utility reaching very low bitrates such as 5.5 kb/s for mono or 7.5 kb/s for stereo at 44.1 kHz with a good perceptual quality. Hence TSAC compresses a 3.5 minute stereo song to a file of 192 KiB.

An Nvidia GPU is necessary for fast operation. CPU only is also supported but slower.

Compression Results

The audio extracts are from here.

Waiting (Pops):

original

stereo 7.26 kb/s

mono 5.61 kb/s

stereo 2.99 kb/s

Greatest_Love_of_All_2min57 (Pops):

original

stereo 6.79 kb/s

mono 5.02 kb/s

stereo 2.84 kb/s

9-Have-big-expensive-car.441 (Pops):

original

stereo 7.81 kb/s

mono 5.91 kb/s

stereo 3.25 kb/s

21-classic.441 (Classic):

original

stereo 6.21 kb/s

mono 4.71 kb/s

stereo 2.57 kb/s

4-Sound-English-male.441 (Voice):

original

mono 6.79 kb/s

mono 3.74 kb/s

mono 2.18 kb/s

Download

Linux version: tsac-2024-04-08.tar.gz. (readme.txt)
Windows version (experimental): tsac-2024-04-08-win64.zip.

Technical information

tsac is based on a modified version of the Descript Audio Codec extended for stereo and a Transformer model to further increase the compression ratio. Both models are quantized to 8 bits per parameter.
The Transformer model is evaluated in a deterministic and reproducible way. Hence the result does not depend on the exact GPU or CPU model nor on the number of configured threads. This key point ensures that a compressed file can be decompressed using a different hardware or software configuration.

Fabrice Bellard - https://bellard.org/