Digital Audio for Films

caveman · 26-01-2004, 20:15

Will digital audio ever be available for NTL SKY films. To my knowledge the only audio output is the RCA audio from the STB which is stereo.

26-01-2004, 20:20

It will not be possible from current boxes, but at some point I would imagine it will be available in the distant future.

caveman · 26-01-2004, 20:29

I don't like that word distant. If my info is correct, in the States they receive 5.1 digital from their cable networks. Why are we always so far behind?

26-01-2004, 20:38

A distinct lack of money available for investment at the moment?

andygrif · 27-01-2004, 11:52

Quote:

Originally Posted by caveman

I don't like that word distant. If my info is correct, in the States they receive 5.1 digital from their cable networks. Why are we always so far behind?

And Sky+ boxes support 5.1 on films they broadcast with it anyway. It would take up a fair amount of extra bandwidth of course.

agentsmith · 27-01-2004, 11:58

Quote:

Originally Posted by andygrif

And Sky+ boxes support 5.1 on films they broadcast with it anyway. It would take up a fair amount of extra bandwidth of course.

not sure it would take up much extra bandwidth tbh

I don't know in what format the current sound is transmitted, but if you look at a dvd, the video content is several gigabytes, but the audio stream in AC3 format is only a few hundred kilobytes.

Bifta · 27-01-2004, 12:41

Quote:

Originally Posted by agentsmith

not sure it would take up much extra bandwidth tbh

I don't know in what format the current sound is transmitted, but if you look at a dvd, the video content is several gigabytes, but the audio stream in AC3 format is only a few hundred kilobytes.

Surely the entire audio content for a film is going to be a little more than a few hundred K?

27-01-2004, 15:09

Quote:

Originally Posted by Bifta

Surely the entire audio content for a film is going to be a little more than a few hundred K?

He means a few kb/s (kilobits per second).

SMHarman · 27-01-2004, 16:20

Quote:

Originally Posted by andygrif

And Sky+ boxes support 5.1 on films they broadcast with it anyway. It would take up a fair amount of extra bandwidth of course.

Not really, if you look at a DVDs composition the audio is about 10% of the total bandwidth.

IMHO digital audion will com with NTL+ and thats "coming soon..."

Stuart · 27-01-2004, 17:08

Quote:

Originally Posted by Bifta

Surely the entire audio content for a film is going to be a little more than a few hundred K?

Yeah, but that's still enough for an extra shopping channel! J/K.

Seriously, I don't think bandwidth would be a problem (I think DD5.1 on most DVDs is encoded at anywhere between 300KBps and 700KBps, DTS goes up to 1.5MBps but NTL would be unlikely to support DTS).

What, I think, might be a problem is the licencing fees Dolby would charge. IIRC, licences to use Dolby aren't cheap.

SMHarman · 27-01-2004, 17:20

Quote:

Originally Posted by scastle

Yeah, but that's still enough for an extra shopping channel! J/K.

Seriously, I don't think bandwidth would be a problem (I think DD5.1 on most DVDs is encoded at anywhere between 300KBps and 700KBps, DTS goes up to 1.5MBps but NTL would be unlikely to support DTS).

What, I think, might be a problem is the licencing fees Dolby would charge. IIRC, licences to use Dolby aren't cheap.

DVD can use up to 8000Kbps for video and 1500Kbps for Audio. Or any other ratio maxing out at 9500 (maybe 10000Kbps). You also need some overhead for subtitles etc.

27-01-2004, 17:27

Quote:

Originally Posted by SMHarman

DVD can use up to 8000Kbps for video and 1500Kbps for Audio. Or any other ratio maxing out at 9500 (maybe 10000Kbps). You also need some overhead for subtitles etc.

MPEG limit is 15Mb/s for video bitrate, is that different for DVD? Probably is limited by the speed its possible to read from the disc.

SMHarman · 27-01-2004, 17:32

Quote:

Originally Posted by Proppinupthebar

MPEG limit is 15Mb/s for video bitrate, is that different for DVD?

I believe the DVD spec allows burst reading of 20Mb/s but optimal disc design works on 10Mb/s At 20M/s you get a heck of a lot less on the disk and the disc / player struggle with error correction / fingerprints etc, as there is no spare overhead to keep the players buffers fed.

This is what I have read from the dvdrhelp site a good few weeks ago and is from memory.

Stuart · 27-01-2004, 18:07

Quote:

Originally Posted by SMHarman

DVD can use up to 8000Kbps for video and 1500Kbps for Audio. Or any other ratio maxing out at 9500 (maybe 10000Kbps). You also need some overhead for subtitles etc.

Yep, I know..

Stuart · 27-01-2004, 18:13

Quote:

Originally Posted by SMHarman

I believe the DVD spec allows burst reading of 20Mb/s but optimal disc design works on 10Mb/s At 20M/s you get a heck of a lot less on the disk and the disc / player struggle with error correction / fingerprints etc, as there is no spare overhead to keep the players buffers fed.

This is what I have read from the dvdrhelp site a good few weeks ago and is from memory.

This is also from Memory. I have a book called DVD demystified, which was written by one of the first DVD authors. He said that the limit as specified by the DVD Forum is 10MBps. The DVD authoring systems we have at work (one of the courses I support is in DVD authoring) will not allow you to encode above 9.99MBps.

As I understand it, the forum specified that limit because the drives available to them at the time (1994-1995) couldn't handle any higher data rates.