I often see reviews of DVDs that list the "bit rate".
For example, Gladiator 2000's DTS Bit Rate is 768. It's Dolby Digital Bit Rate is 448....
What does these number mean?

Thanks in advance!

The bit rate is the amount of data being put out by the DVD in audio and video. My Sony displays the audio and video separately. Your numbers must be for the audio as they're too low for video.

DTS is much less compressed than DD so you will get higher bit rates when playing it. That's one reason people prefer DTS.

...A rather silly reason to prefer one format over the other and not a factor in the possibility of DTS being sonically superior (read more accurate) than Dolby Digital. Everything depends on the quality and accuracy of the coding process (codec)...

The DVD spec allows for 10.08 Mbps, or 10.08 megabits per second (note: a bit is different than a byte, eight bits in a byte) of total data rate. Of this amount the following have to factor in:

Video
Subtitles - 8kbps per language
Dolby Digital 5.1 - 384 or 448kbps (Dolby Digital 5.1 is capable at 256kbps but is extremely rare)
Dolby Prologic or Stereo - 192kbps
Commentary (mono) - 32kbps
DTS (full rate) - 1536kbps
DTS (half rate) - 768kbps

Dolby Digital and DTS allocate data from their “bit pool” to different channels in very different manners and to explain data allocation fully would take several pages. I suggest that if you are technically minded and interested you read the white paper on Coherent Acoustics on DTS’ website. Topics such as sub bands, bit pool, and data allocation are addressed.


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