HD fans: Whats DD5.1 format?

[peeruser]

Hi There,
I usually download 720p x264 files and I noticed the DD5.1 format.
Can anyone tell me what it means? I see the files are very large. Does it require a strong machine?
Thanks.

[The Flying Cow]

That just means those releases have Dolby Digital Surround Sound 5.1 Audio support, much like DVDRs.

Hope that helps.

[peeruser]

Than why are the files so large? For example, Lost S04E09 720p HDTV DD5.1 x264-M794 is 2.24 GB while the file without the DD5.1 is only 1.09 GB.

[DKre8ive1]

It most likely has to do with the bit rate that audio has which is probably much higher for 720 which comes from an HD source compared to the one with out that probably has MP3 audio which is far more compressed.

Applications of Dolby Digital
The system is used in many bandwidth-limited applications other than DVD-Video, such as digital TV. The AC-3 standard allows a maximum coded bit rate of 640 kbit/s. 35 mm film prints use a fixed rate of 320 kbit/s. HD-DVD and DVD-Video discs are limited to 448 kbit/s, although many players can successfully play higher-rate bitstreams (which are non-compliant with the DVD specification). ATSC and Digital cable standards limit AC-3 to 448 kbit/s. Blu-ray Disc, the Sony PlayStation 3 and the Microsoft Xbox game console can output an AC-3 signal at a full 640 kbit/s. Some Sony PlayStation 2 console games are also capable to output AC-3 standard audio as well.

Link-> http://en.wikipedia.org/wiki/Dolby_Digital

Codec : MPEG-1 Audio layer 3
Codec profile : Joint stereo
PlayTime : 42mn 13s
Bit rate : 130 Kbps
Bit rate mode : VBR
Channel(s) : 2 channels

hope that helps.

[ElitUser]

Happy to know about DD5.1 format