There's no difference because DTS can be 5.1 too. Difference is between the compression size. DTS is compressed 1:4 ( like a normal sound from CD 1411 kb/s ) Dolby Digital is compressede 1:12 and have less dynamic and details. 5.1 is only a mark which gives us information about a number of channels. 5=five channels ( front left, right, center, left and right surround, number 1 after the dot is a number of sub level channels. DTS and DD can be 5.1, DD also can be 5.1 EX and DD HD 7.1 , DTS can be 6.1 too and DTS HD 7.1. More u can find here DTS:
http://www.dtsonline.com/.
and DOLBY DIGITAL:
http://www.dolbydigital.com/
It's good that the new releases of DVD are finally mixed in true 5.1 channel. Taht gives us a lifelike sound and atmosphere of TD concerts at home.
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