ARE THERE ANY DIFFERENCES IN SOUND QUALITY BETWEEN THE THREE HD AUDIO CODECs?
LPCM soundtracks on Blu-Ray Disc and HD-DVD are not compressed. Dolby TrueHD and DTS-HD Master Audio are lossless codecs. They are compressed versions of the PCM track.
The maximum uncompressed bit rates for a movie soundtrack are approximately:
48,000(samples per second) x 16(bits per sample) x 6(channels) = 4.6Mbps
48,000(samples per second) x 20(bits per sample) x 6(channels) = 5.8Mbps
48,000(samples per second) x 24(bits per sample) x 6(channels) = 6.9Mbps
48,000(samples per second) x 16(bits per sample) x 8(channels) = 6.1Mbps
48,000(samples per second) x 20(bits per sample) x 8(channels) = 7.7Mbps
48,000(samples per second) x 24(bits per sample) x 8(channels) = 9.2Mbps
Dolby TrueHD and DTS HD MA can go up to
96,000(samples per second) x 24(bits per sample) x 8(channels) = 18.4Mbps
Please remember that since both CODECs use variable bit rates, we cannot calculate the average bit rate of a typical soundtrack. In addition, Dolby TrueHD and DTS MA use different compression algorithms and on the average use less than the maximum numbers.
Theoretically, LPCM, Dolby TrueHD, and DTS Master Audio should sound the same if they are encoded at the same number of bits and sampling frequency (16 bits, 48 KHz for example). Any difference that you may hear are due to channel volume differences.
Decoded Dolby TrueHD = Decoded DTS HD MA = Uncompressed LPCM
In the future, we will see less LPCM titles (especially at 24-bit, 96KHz, and 7.1-channels) since this will require a lot of disc space. TrueHD and DTS Master Audio are encoded at variable bit rate and compressed, leaving more disc space for better picture quality and more extras.