[thomaspf]

Here is a entry level overview of the encoding of multichannel material into S/PDIF.

The resulting payload is equivalent to a 16bit/48Khz uncompressed PCM stream with a few flags in the headers set to identify the stream type.

Most sourround receivers analyze the stream in real time and will automatically switch to surround mode independent of the header flags if they detect the samples to contain encoded sourround material. That is how the popular test for bit perfect playback works. These tracks just look like standard 2 channel PCM files to the system but the receiver switches to surround mode anyhow.

So from a USB sound card perspective all it needs to supports is 16bit/48Khz to pass through encoded sourround streams to an S/PDIF interface.

Cheers

Thomas

 

[gregorio]

Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif yeah, that is 24-bit, thats what I'm asking gregorio about, as USB devices aren't going to decode DTS or DD (very few will), and they aren't going to handle 24-bit audio (again, very few will)

OK, I should start out by saying that I've never actually used the new high definition DTS or Dolby encoding systems so my knowledge is rather limited. AFAIK, professionally the new HD systems are only being used on some Blu-Ray disks. For film, DD is actually printed onto the film itself and 448kbps is about the limit. DTS isn't printed onto the film but has a synchronized disk which is supplied to cinemas along with the distribution print, which is why it manages higher data rates. Again, AFAIK, standard DVDs only support DD and DTS, not the new HD formats.

DD and DTS are both highly compressed formats which are initially fed a 16bit 48kFs/s signal. However, what comes out the end is not a fixed bit depth (like with MP3s). AFAIK, the HD versions also employ some data compression but they can accept 24bit 96kFs/s. Again though, I'm reasonably sure that it's limited to Blu-Ray, rather than standard DVD as the amount of data generated would be too high for DVD unless it was very heavily data compressed.

G

 

[obobskivich]

Quote:

Originally Posted by gregorio /img/forum/go_quote.gif OK, I should start out by saying that I've never actually used the new high definition DTS or Dolby encoding systems so my knowledge is rather limited. AFAIK, professionally the new HD systems are only being used on some Blu-Ray disks. For film, DD is actually printed onto the film itself and 448kbps is about the limit. DTS isn't printed onto the film but has a synchronized disk which is supplied to cinemas along with the distribution print, which is why it manages higher data rates. Again, AFAIK, standard DVDs only support DD and DTS, not the new HD formats. DD and DTS are both highly compressed formats which are initially fed a 16bit 48kFs/s signal. However, what comes out the end is not a fixed bit depth (like with MP3s). AFAIK, the HD versions also employ some data compression but they can accept 24bit 96kFs/s. Again though, I'm reasonably sure that it's limited to Blu-Ray, rather than standard DVD as the amount of data generated would be too high for DVD unless it was very heavily data compressed. G

DTS 24-bit is found on some DVDs (DTS 96/24 is not one of the new HD formats, that'd be Master Audio), so thats where my concern would lay

and HD-DVD gets HD audio as well

 

[gregorio]

Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif DTS 24-bit is found on some DVDs (DTS 96/24 is not one of the new HD formats, that'd be Master Audio)

Standard DTS on DVD is not 24bit. The data rate for DTS on a DVD is 754kbps (very rarely 1.5mbps). 16bit 44.1kFs/s on a CD is roughly 1.4mbps and is only encoding 2 channels. Generally DTS uses half that data rate of CD to encode 6 channels (5.1) as opposed to 2, so it is a very lossy compressed format and not far off what you might expect from say a 192kbps VBR MP3.

You can feed a 24/96 mix into a DTS encoder but what comes out is definitely not 24/96! Think about it for a moment, 6 channels of 24/96 uncompressed would in theory need about 13mbps but it is reduced to just 754kbps, that's some pretty serious lossy compression!! Don't forget that the maximum data rate for a DVD is about 9.8mbps and that includes the visuals as well as the audio!!

G

 

[obobskivich]

Quote:

Originally Posted by gregorio /img/forum/go_quote.gif Standard DTS on DVD is not 24bit. The data rate for DTS on a DVD is 754kbps (very rarely 1.5mbps). 16bit 44.1kFs/s on a CD is roughly 1.4mbps and is only encoding 2 channels. Generally DTS uses half that data rate of CD to encode 6 channels (5.1) as opposed to 2, so it is a very lossy compressed format and not far off what you might expect from say a 192kbps VBR MP3. You can feed a 24/96 mix into a DTS encoder but what comes out is definitely not 24/96! Think about it for a moment, 6 channels of 24/96 uncompressed would in theory need about 13mbps but it is reduced to just 754kbps, that's some pretty serious lossy compression!! Don't forget that the maximum data rate for a DVD is about 9.8mbps and that includes the visuals as well as the audio!! G

greg, I get all of that

simple statement: who gives a damn, its still encoded as 24-bit, and its still 24-bit data

 

[thomaspf]

I believe it is actually encoded into a 16 bit stream. You only get 24 bits after the decoding in the receiver.

Cheers

Thomas

 

[obobskivich]

Quote:

Originally Posted by thomaspf /img/forum/go_quote.gif I believe it is actually encoded into a 16 bit stream. You only get 24 bits after the decoding in the receiver. Cheers Thomas

uh? what?

you can't turn 16 into 24 (and it doesn't do a thing for accuracy/quality either), without upsampling/resampling it (and thats about the same thing as transcoding), so you're basically saying its "a scam"?

the wiki on it isn't very specific on implementation details:
DTS 96/24 allows the delivery of 5.1 channels of 24-bit, 96 kHz audio and high quality video on the DVD-Video format. Prior to the invention of DTS 96/24, it was only possible to deliver two channels of 24-bit, 96 kHz audio on DVD-Video. DTS 96/24 can also be placed in the video zone on DVD-Audio discs, making these discs playable on all DTS compatible DVD players.

but that seems to denote that it isn't resampled or "decoded to 24-bit" (thats not even logical)

from DTS themselves:
The disc is encoded with DTS 96/24 and is playable in 96/24 with any DTS 96/24-equipped hardware. Fully compatible with DTS-capable 5.1 hardware, and backward-compatible (at 48/24) to all DTS-equipped hardware.

in other words, it sounds like 24-bit is actually being used and sent along as the bitstream

link to DTS website page:
DTS | Technology | DTS 96/24

 

[thomaspf]

Well, a full rate DTS96/24 stream is 1.536Mbit/s. That data contains all surround channels in an extremely compressed format. As it turns out that is the maximum data rate a 2 channel x 16 bits x 48000 Khz stream can carry.

All surround streams from a Video DVD travel encoded as 16bit 48Khz over S/PDIF. Lower rate formats are padded with lots of zeros. No upsampling or resampling just extremely high compression. The DTS site has marketing but no technical information.

Cheers

Thomas

 

[gregorio]

Quote:

Originally Posted by obobskivich /img/forum/go_quote.gif greg, I get all of that simple statement: who gives a damn, its still encoded as 24-bit, and its still 24-bit data

Sorry Bob, that's my point, it is not still 24bit. It's quite simple, look at the maths:

24bit x 96,000 = 2,304,000 (bits per second) x 6 (channels) = 13,824,000

13,824,000 is just under 13.2mbps. Now the actual data rate of DTS 96/24 is 1.5mbps. What has happened to the other 11.7 mega bits of data per second? Some of the missing 11.7mbps can be accounted for by lossless compression but most is lost. DTS and DD are lossy data compression formats and therefore quite a bit of this 11.7meg is discarded. It is impossible for the decoded DTS datastream to still be 24/96 just as it is impossible for a 192kbps MP3 to still have 16bit 44.1k of the original CD.

The wording on the link to DTS' website is very misleading and cleverly done. Most of the wording explains the difference between 16bit and 24bit, it does not actually say that DTS 96/24 is 24bit or 96kFs/s it just says at the end: "When played back on a DTS 96/24 capable receiver, DTS 96/24 content delivers better frequency response, tonal accuracy, and dynamic range."

I agree that it's likely to sound better as it is using double the data rate of standard DTS; 754kbps vs 1.5mbps. But this is not the 13.2mbps required for 24bit 96kFs/s!!

So they are using the fact that the signal before encoding is 24bit-96kFs/s to imply that what comes out after decoding is also 24bit 96kFs/s but of course it can't be otherwise it would be a lossless encoding algorithm. But no lossless compression algorithm exists which can reduce 13.2mbps to 1.5 mbps and besides, DTS in it's own technical papers states that the compression algorithm is lossy. The exact process of how and what is discarded is a trade secret, so I don't know the details. Clever marketing and IMO, very misleading but probably not quite against the law.

G

 

[obobskivich]

I understand that its not 13.2 mbps, but what I'm saying is that 24/96 DTS content won't play on 16/48 DTS decoders (I know, I own one), so who knows what they're really doing, but suffice to say "its different"

idk, its misleading for sure, and I have no details on implementation, but it was just something that came to mind

 

[thomaspf]

Actually..

DTS96/24 tracks should play just fine on decoders that only support the 24/48 DTS format.

DTS96/24 is a layered codes with a standard 24/48 core layer that should be compatible with all DTS decoders. Instead of padding the remaining 16bit/48Khz bandwidth with zeroes, the DTS96/24 format adds a secondary data stream that encodes frequency information over 24Khz.

A DTS96/24 capable decoder will put these two streams together to produce a full 24/96 signal but a plain DTS capable decoder should at least pick up the core stream and give you a 24/48 signal.

Cheers

Thomas

 

[obobskivich]

Quote:

Originally Posted by thomaspf /img/forum/go_quote.gif Actually.. DTS96/24 should play just fine on decoders that on support the 24/48 DTS format.

reading is fun, I said "16/48", so I'm not even gonna respond or read the rest of your post, because actually, you're wrong

and even if it plays on 24/48 decoders, whats USB limited to? 16-bit what? oh, sorry, forgot about that being my original point, sort of can't hear a damn thing over the "big willy" contest we've got going on

 

[thomaspf]

@obobskivich

Is there such a thing as a 16/48 DTS decoder? What actual surround sound device are you using? If it has a DTS logo on it should play DTS96/24 streams.

Surround tracks on video DVDs are encoded in a 16bit/48Khz stream and that is how they travel over S/PDIF in pass through. Any other resolution or sample rate is being derived at the surround receiver after decompressing the data. This works just fine over a suitable USB->S/PDIF adapter.

I am unaware of anything going on and I have been wrong before..

I thought I am explaining how this actually works and I think the rest of the forum would appreciate if you could point out if there are any problems with my statements. Can you point to any technical documentation that would support your critique? There a very many users out there that have their surround sound receivers connected via USB->S/PDIF devices. The turtle beach Audio Advantage is one pretty cheap example.

Cheers

Thomas

 

[obobskivich]

Quote:

Originally Posted by thomaspf /img/forum/go_quote.gif @obobskivich Is there such a thing as a 16/48 DTS decoder? What actual surround sound device are you using? If it has a DTS logo on it should play DTS96/24 streams. Surround tracks on video DVDs are encoded in a 16bit/48Khz stream and that is how they travel over S/PDIF in pass through. Any other resolution or sample rate is being derived at the surround receiver after decompressing the data. This works just fine over a suitable USB->S/PDIF adapter. I am unaware of anything going on and I have been wrong before.. I thought I am explaining how this actually works and I think the rest of the forum would appreciate if you could point out if there are any problems with my statements. Can you point to any technical documentation that would support your critique? There a very many users out there that have their surround sound receivers connected via USB->S/PDIF devices. The turtle beach Audio Advantage is one pretty cheap example. Cheers Thomas

I'm using a Technics SH-AC500D, which is 16/48, DTS licenced, and will not decode 24/96 content (as my token one DVD (out of ~100) with 24/96 will not playback in DTS (this is how minimal DTS 24/96 is...

))

honestly, I don't have any technical information either way for 24/96 being "real 24-bit" or some marketing voodoo (for example, is it just resampling to 24-bit in the reciever, and thats the licenced technology? or is it some very very lossy compression from 24-bit? or is it mastered in 24-bit? or what), and I know many users do have things working "just fine", so I'm not debating that, I was just bringing 24/96 up, not that its a "massive" problem (although I have seen grown men break down and cry over DTS not being supported on a given system

, sadly I'm not kidding) , honestly I don't have an answer, all of your information is "good" or "sound" (I'm not at all trying to attack your credibility, I just wanna know the complete answer

), from what I've read, DTS (the company) doesn't really want to give up their secrets, nor do they want to agree with the actual #'s (i.e: greg's calculations, or the #'s that Dolby/DVD Forum show as maximum bitrate for a DVD)

so I guess sum it up to: I have no bloody idea.

 

[thomaspf]

Sounds cool, thanks for sticking with this.

A couple of years back I conducted this experiment. Instead of plugging the optical output of my sound card into my receiver I recorded the stream with a different sound card set to 16 bit/48Khz as the recording format and clocked to the incoming signal.

The recording application took any AC3 or DTS track as a 16/48 2 channel stream. Then I saved this into a 16/48 WAV stereo file and played this file with a bit perfect player. On my system that worked just fine and the surround track was fully intact.

It took a bit of fiddling to make sure this was a bit perfect recording. When the recording format was set to 24/48 the lower 8 bits of each sample were zeros.

I have not done this in a while but maybe I try it again on the weekend just to make sure.

Cheers

Thomas