De-Facto/Industry Audio Compression Standards

Dolby Digital ("formerly" AC3)

CD quality requires 128-192 kb/s

psychoacoustic transform coder
    fixed time-division aliasing cancellation filter bank
    512/256 (10 msec) overlapping window
hybrid backward/forward adaptive bit allocation
    psychoacoustic assumptions in the decoder
switchable spectral envelope delta (coef-changes) coding D15/D25/D45

Selection of Audio Coding Technologies for Digital Delivery Systems (Dolby spin)

Real Audio 3.0 (Real Networks)

DVD-Video Standard

2.6/5.2 GB

DVD-Video Audio tracks, each of eight tracks can be:
    Dolby Digital (formerly AC-3): 1 to 5.1 channels (many discs)
        48 kHz, 24 bits/sample, 64-448 kb/s (384 kb/s for 5.1 channels, 192 kb/s for stereo)
    MPEG-2 audio: 1 to 5.1 or 7.1 channels (few discs)
        MPEG-1 Layer III and MPEG-2 AAC not supported
    PCM: 1 to 8 channels (some discs)
        48 or 96 kHz, 16/20/24 bits/sample


DMX - Digital Music Express
95 music programs over TCI cable service


CD quality requires more than 256 kb/s (5:1 compression)

512-sample frame
3 subband QMF filters with MDCT 128 (0-5.5kHz) + 128 (5.5-11kHz) +  256 (11-22kHz)
block switching: 11.6 ms long block (LMH) vs. 2.9ms(L) + 2.9ms(M) + 1.45ms(H) short blocks
coefs quantized by word length and scale factor

ATRAC: Adaptive Transform Acoustic Coding for MiniDisc

MiniDisc - MD

140 MB, 74 minutes

While the U.S. market is gloomy, MiniDisc is doing better worldwide, especially in Japan.

The Rewriteable MiniDisc System
The MiniDisc Community Page
Yahoo! : Entertainment : Audio : MiniDisc - with links to Australia, Czech Republic, Finland, Japan, and USA
    mirror sites.

NoBell Home - gjm - last update 02/08/1999