Bit Sliced Arithmetic Coding (BSAC)

Bit-Sliced Arithmetic Coding (BSAC) is an audio coding algorithm developed by Samsung [1] to offer fine-grain bitrate scalability. It is part of the MPEG-4 standard [2] and demonstration software can be compiled from the publicly-available MPEG-4 Reference Software (2001 Edition).

The following single-channel sound files compare coding efficiencies of BSAC and Scala codecs at two different bitrates. All files are approximately 6 seconds in length with 44.1 kHz sample rate; samples are presented both as compressed bitstreams and uncompressed (decoded) .wav files. For verification, the BSAC bitstreams can be decoded using an MPEG-4 reference software decoder, while Scala bitstreams can be decoded using the demonstration decoder software available from this site.


Signal Original file
  Mono Bitrate
32 kbit/s 64 kbit/s
harpsichord harp.wav bitstream harp32.mp4 harp32.sab harp64.mp4 harp64.sab
decoded wav harp32_bsac.wav harp32_sac.wav harp64_bsac.wav harp64_sac.wav
female voice voice.wav bitstream voice32.mp4 voice32.sab voice64.mp4 voice64.sab
decoded wav voice32_bsac.wav voice32_sac.wav voice64_bsac.wav voice64_sac.wav
castanets cast.wav bitstream cast32.mp4 cast32.sab cast64.mp4 cast64.sab
decoded wav cast32_bsac.wav cast32_sac.wav cast64_bsac.wav cast64_sac.wav


For some signals such as harpsichord, BSAC performance at 64 kbit/s is similar to the Scala codec. However BSAC suffers from poor coding efficiency at lower bitrates, indicated by the 32 kbit/s samples where the Scala codec achieves significantly better coding quality for all three test signals. Error-resilient coding is a further advantage of the Scala codec.


[1] S. H. Park et al., "Multi-Layer Bit-Sliced Bit Rate Scalable Audio Coding," presented at the 103rd Convention of the Audio Engineering Society, New York, paper 4520 (1997 Sep.).

[2] ISO/IEC JTC1/SC29/WG11 N2803, "MPEG-4 Audio Version 2 (Final Committee Draft 14496-3 AMD1)", Vancouver, Canada (1999 July).