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AC3/DTS Talk, thread split
David Nordin
post Nov 24 2003, 22:02
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AC-3 is most common at 448kbps, in some countries 384kbps. At cinemas it's 640kbps.
DTS is most common at 141xbkps and is VBR capable, altho uncommon. It's clearly not useful in this context - AC3 is far more likely to candidate.
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2Bdecided
post Nov 25 2003, 11:20
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QUOTE (MTRH @ Nov 24 2003, 09:02 PM)
AC-3 is most common at 448kbps, in some countries 384kbps. At cinemas it's 640kbps.

IIRC it's only 384kbps in cinemas because that's as much information as they could fit between the film sproket holes.

Cheers,
David.
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David Nordin
post Nov 25 2003, 12:12
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yes, my mistake - I must have mixed it it with something else, altho I'm pretty sure the format is 640 capable, blah.


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rjamorim
post Nov 25 2003, 12:12
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QUOTE (2Bdecided @ Nov 25 2003, 08:20 AM)
IIRC it's only 384kbps in cinemas because that's as much information as they could fit between the film sproket holes.

On cinemas: 640kbps
On laser discs: 384kbps
On DVDs: Usually 224, 384 and 448kbps
http://www.mp3-tech.org/ac3.html

IIRC, AC3 isn't recorded inbetween sproket holes. SDDA is.


One thing worth mentioning here is that AC3 doesn't cope well with VBR. Although the standard allows it, several decoders choke on VBR streams.

I did a test at doom9 once: Using a patched ac3enc.dll (thanks to S_O) that outputs VBR streams (it just randomizes the bitrates), I encoded a multichannel stream and tested it with several decoders.

ac3dec worked
liba52 (valex's filter) worked
azid didn't work (error message, IIRC)
Dolby decoders (CyberLink, Intervideo) didn't work (crash)

I couldn't get anyone to test it on a receiver.

Regards;

Roberto.

This post has been edited by rjamorim: Nov 25 2003, 12:17


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seanyseansean
post Nov 25 2003, 12:44
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QUOTE (2Bdecided @ Nov 25 2003, 10:20 AM)
QUOTE (MTRH @ Nov 24 2003, 09:02 PM)
AC-3 is most common at 448kbps, in some countries 384kbps. At cinemas it's 640kbps.

IIRC it's only 384kbps in cinemas because that's as much information as they could fit between the film sproket holes.

Cheers,
David.

I think you're right, DTS doesn't have this limitation being delivered on CDs along with the film.
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Lefungus
post Nov 25 2003, 13:37
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But dts store synchronisation informations between the film sprocket holes


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seanyseansean
post Nov 25 2003, 14:03
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QUOTE (Lefungus @ Nov 25 2003, 12:37 PM)
But dts store synchronisation informations between the film sprocket holes

Yes, it stored timecode there.
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2Bdecided
post Nov 25 2003, 14:26
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Well, Dolby seem to think they store AC-3 data between the sprocket holes...
http://www.dolby.com/tech/m.ot.0006.Filmgo...goerFAQ.html#q3


Can anyone provide another reference for the bitrate of AC-3 on film prints? i.e. a reference that says "Dolby" at the bottom, rather than "Gabriel" wink.gif (no offence Gabriel - maybe you can just let us know where you took your information from).

Cheers,
David.
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niktheblak
post Nov 25 2003, 15:46
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SDDS is stored in the outer edge of the film, outside the sprocket holes. AC3 is stored between sprocket holes.

www.brooklyncenter.com/cinema/wdts.htm
www.sdds.com / What is SDDS?
www.mkpe.com/articles/1999/Multichannel/multichannel.htm
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AgentMil
post Nov 25 2003, 15:49
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DTS, Dolby Digital and DVD

What is Dolby Digital (AC-3)

(Qoutes from the second link)
"In order to retain an analog track so that these prints could play in any cinema, it was decided to place the new digital optical track between the sprocket holes, a key factor in defining its maximum practical bit-rate."

"Data rates range from as low as 32 kb/s for a single mono channel to as high as 640 kb/s..."

This allows us to determine that 640kbps is the maximum allowed bitrate for Dolby Digital on film prints, as Dolby Digital was designed for cinema first then the home market second. Also tells us that the optical track was placed between the socket holes.

Another note to mention the standard viable bitrate for Dolby Digital on film prints is 320kbps.

(Quote from first link)
"The more aggressive compression system utilised by Dolby's system allows a 5.1-channel soundtrack to function with a recommended minimum bitrate of only 320kbps. That's a compression factor of 15:1 (at 20-bit/48kHz), an extremely impressive technical feat."

The first link will tell you that DTS soundtrack is located on an optical medium and the timestamps held between the optical soundtrack and picture area for synching.

(Quote from first link)
"DTS, unlike AC-3, is not recorded on the film itself. Instead, DTS is stored on CD-ROM and synchronised with the film using standard SMPTE time codes, located between the film's optical soundtrack and picture area."

All of this is 99% accurate based on the data that I have located and interpreted.

BTW There is a film manual in PDF format that was located on Dolby's website that seems to have ALOT of information in it based on a few websites that I have found directly quoting from it. The file name is "encodvw.pdf" and the title "The Dolby Professional Encoding Manual", please post any information if you managed to find or have a copy of it.

**EDIT**
Looks like Dolby just rearranged their site so here is the Encoding Manual direct link.

The Dolby Professional Encoding Manual PDF Format Optimised for Screen Viewing.

Regards

AgentMil

This post has been edited by AgentMil: Nov 25 2003, 16:07


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rjamorim
post Nov 25 2003, 16:07
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QUOTE (rjamorim @ Nov 25 2003, 09:12 AM)
I did a test at doom9 once: Using a patched ac3enc.dll (thanks to S_O) that outputs VBR streams (it just randomizes the bitrates), I encoded a multichannel stream and tested it with several decoders.

In case someone is wondering, here is the thread:
http://forum.doom9.org/showthread.php?s=&t...&threadid=33966

I can upload the patched AC3enc DLL is someone is interested.

Also, I would like to invite anyone with a receiver to test VBR decoding

This is the VBR stream, from "The Wall" DVD:
http://pessoal.onda.com.br/rjamorim/Test.ac3

You'll notice some times the quality drops badly. You'll understand why if you read the thread at doom9 :B

If you test it, please report:
-Brand and model of receiver
-What you used to send the stream over S/PDIF. I know Moonlight Odio Dekoda can decode VBR, but I don't know if it can send it over S/PDIF.

Thanks.

Regards;

Roberto.


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Gabriel
post Nov 25 2003, 17:05
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QUOTE
(no offence Gabriel - maybe you can just let us know where you took your information from)

It was from Dolby. But it was something like a "white paper", not a technical paper. As you know, white papers sometimes have a marketing taste.
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2Bdecided
post Nov 25 2003, 17:58
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The reason I asked is because I thought I'd heard Dolby people say 384kbps.

Now I've looked it up, the 1994 Amsterdam AES paper "AC-3: Flexible Perceptual Coding for Audio Transmission and Storage" by C C Todd et al (I have a pre-preprint, so don't have the actual preprint number) says 320kbps...

"It was determined that 320 kb/s of error corrected audio data could be reliably placed and extracted from the film are between the sprocket hole perforations on one side of the 35mm film."

later, discussing (promoting?) the expected widespread use of AC-3 outside the cinema, it start...
"The requirement which AC-3 had to meet to satisfy the cinema application are straightforward. AC-3 only has to support one bit-rate (320 kb/s) and audio coding move (5.1 channels)."

So unless the six authors of this paper let this through by accident, or the specification was later ammended, it seems to be 320kbps.

I find that strange. I always thought the reason so many DVDs ended up with 384kbps tracks was because they were copied from the original film, but that could be totally wrong.

I think I might just ask them...

Cheers,
David.
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sthayashi
post Nov 25 2003, 20:01
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[Note to admins: this message should be split as well as the one from Roberto]

I tested Roberto's VBR-AC3 file with my receiver, a Yamaha HTR-5590. I tested with both PowerDVD 5 and Foobar 2000. Fb2k had a problem displaying time, and doesn't properly do S/PDIF out (at least not with directSound wink.gif ), but the actual playback great (it just sounds like it's been downmixed to stereo).

I used PowerDVD 5 to output the AC3 via S/PDIF optical to my receiver. It appeared to be perfectly capable of handling the S/PDIF without a problem. The receiver certainly played it back without causing a problem.

I would encourage anyone who can to test out their system and report the results. Thanks.
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Krobar
post Dec 12 2003, 22:08
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Id be happy to test the files on my Pioneer multi channel amp, just point me to where they are (The link appears broken).

The 640KB/sec is the max for dolby, D-Theater tapes run Dolby at this rate, on decent systems there is an improvement over the standard 448 DVD rate.

Edit:
Fixed the DTS prob.

This post has been edited by Krobar: Dec 12 2003, 23:44
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plonk420
post Mar 29 2004, 15:38
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QUOTE (seanyseansean @ Nov 25 2003, 06:03 AM)
QUOTE (Lefungus @ Nov 25 2003, 12:37 PM)
But dts store synchronisation informations between the film sprocket holes

Yes, it stored timecode there.

incorrect, DTS timecode is between the picture frame and the Dolby SR (analog) tracks.

edit: shit .. bumped an old post

anywho, as i work at a theater, DD is stored between a sprockets and supposedly is "highly" encrypted (according to a tech i asked). DTS, i mentioned, and SDDS is on the very edges of the film and (now i'm digging really deep into long term memory) runs at 3mbits/sec, but most of it is redundant(/parity?) information as this part of the film gets the most abuse (there are all sorts of straps and rollers this part of the film travels over as it goes thru a projector). so even 3mbits of data can't survive even as little as several weeks at theaters.

and 320kbits or 384kbits (320 sounds familiar to me), whatever it is, it sounds like shit (anyone see Kings of Comedy in a DD house? it was like the applause codec killer sample) .. even theater-DTS isn't as good as i thought .. i've heard artifacts once or twice in passages where stringed instruments were being played... (however, that's like once or twice out of hundreds of DTS movies i've screened)

edit2: also, i hear film duping houses are going to make/rent prints with SDDS only on demand as they're becoming less and less in demand... (that from a tech's mouth, this year)

This post has been edited by plonk420: Mar 29 2004, 15:50
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plonk420
post Mar 29 2004, 16:24
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http://www.plonkmedia.com/frame_of_film.jpg

http://www.plonkmedia.com/frame_of_film.png
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rjamorim
post Mar 29 2004, 16:49
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QUOTE (Krobar @ Dec 12 2003, 06:08 PM)
Id be happy to test the files on my Pioneer multi channel amp, just point me to where they are (The link appears broken).

In case anyone is still interested in testing it with receivers, I uploaded the VBR AC3 test stream to the same location again.

This post has been edited by rjamorim: Mar 29 2004, 16:50


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joopv
post Apr 5 2004, 23:37
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I'd love to test this (already downloaded) with my Pioneer vsx908. Now if i only had a way to send this ac3 data over the spdif port of my sound card to my receiver.
I can play dts-encoded wav files very nicely using winamp and sound output redirected to the spdif port.
Now how do i do this with ac3 files ?

This post has been edited by joopv: Apr 5 2004, 23:38
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rjamorim
post Apr 6 2004, 02:27
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QUOTE (joopv @ Apr 5 2004, 07:37 PM)
Now how do i do this with ac3 files ?

I guess you can load the AC3 on a DVD software player (WinDVD, PowerDVD). Then, configure the player to send audio through S/PDIF. Should work.


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joopv
post Apr 6 2004, 07:37
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Powerdvd 5 does not recognise my s/pdif port as such - i have no idea why it doesn't.
However - when i choose in 'sound and multimedia properties' control panel the s/pdif card as preferred output device it works, but then i'm using the ac3 decoder from Powerdvd and a normal stereo stream is sent to the Pioneer receiver.
I think my old ISA s/pdif soundcard is not compliant with newer standards.

Is there a way to convert the ac3 file to a (48kHz) wav file so i can try this anyway? I know this works - i have some 48kHz formatted wav files with ac3 content. Rather inefficient but playable on my system.

http://www.modernrecording.com/articles/20...pr/cd-ac3.shtml
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Norman
post Apr 6 2004, 09:28
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Roberto, my Marantz SR7000 decoded the ac3 file just fine. This doesn't surprise me, however biggrin.gif

Edit: forgot to add the software I used: Media Player Classic + ac3filter.

Norman

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Pontoppidan
post Apr 6 2004, 11:39
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hello!
I have testet the file with my Marantz SR 6300..! I can play it via my S/PDIF, but there are a problem in the middel of the track there are some crappy noises.. crying.gif I have played the file with Powerdvd 5..

Phil

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rjamorim
post Apr 6 2004, 15:21
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QUOTE (Pontoppidan @ Apr 6 2004, 07:39 AM)
I can play it via my S/PDIF, but  there are a problem in the middel of the track there are some crappy noises.. crying.gif

That's expected. The VBR routine being employed by the test encoder I used just randomizes bitrates. So, some parts of that stream are being encoded at 32kbps.

QUOTE
Is there a way to convert the ac3 file to a (48kHz) wav file so i can try this anyway? I know this works - i have some 48kHz formatted wav files with ac3 content. Rather inefficient but playable on my system.


That's strange.

One solution would be getting the in_ac3 Winamp plugin:
http://winampac3.sourceforge.net/

Then use the Winamp diskwriter to decode the AC3 stream to Wav.


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Thor
post Apr 11 2004, 15:49
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QUOTE (plonk420 @ Mar 29 2004, 03:38 PM)
QUOTE (seanyseansean @ Nov 25 2003, 06:03 AM)
QUOTE (Lefungus @ Nov 25 2003, 12:37 PM)
But dts store synchronisation informations between the film sprocket holes

Yes, it stored timecode there.

incorrect, DTS timecode is between the picture frame and the Dolby SR (analog) tracks.

edit: shit .. bumped an old post

anywho, as i work at a theater, DD is stored between a sprockets and supposedly is "highly" encrypted (according to a tech i asked). DTS, i mentioned, and SDDS is on the very edges of the film and (now i'm digging really deep into long term memory) runs at 3mbits/sec, but most of it is redundant(/parity?) information as this part of the film gets the most abuse (there are all sorts of straps and rollers this part of the film travels over as it goes thru a projector). so even 3mbits of data can't survive even as little as several weeks at theaters.

and 320kbits or 384kbits (320 sounds familiar to me), whatever it is, it sounds like shit (anyone see Kings of Comedy in a DD house? it was like the applause codec killer sample) .. even theater-DTS isn't as good as i thought .. i've heard artifacts once or twice in passages where stringed instruments were being played... (however, that's like once or twice out of hundreds of DTS movies i've screened)

edit2: also, i hear film duping houses are going to make/rent prints with SDDS only on demand as they're becoming less and less in demand... (that from a tech's mouth, this year)

I've found a site that gives very detailed information on cinema systems.
Unfortunately it's in German, which I don't really speak or understand myself but for those who do, I wanted to share this anyway.
The site shows detailed photo's of movie frames and the different audio tracks on them.
Link: http://www.kinoteam.de/kt/
The audio systems page is here: http://www.kinoteam.de/kt/kt_tonsysteme.html
Oh by the way, of course BabelFish can help to understand it if you don't know German.
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