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Old 7th January 2011, 22:05   #1  |  Link
A.Fenderson
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DTS (& 640kbps AC3) encoding software questions, esp. as re. Blu-ray

It seems like some people who likely find DTS 1.5Mbps a sweet-spot for quality vs. bitrate for surround-encoding are reencoding some of their lossless BD audio tracks to core DTS for their backups using BD-RB, or going to MKV, etc. I am considering this route myself (generally to BD25 via BD-RB), but have some questions for those in the know.

As of right now, the SurCode DVD-DTS application is $249 direct from the developer (slightly cheaper elsewhere). It seems to encode 1.5Mbps/756Kbps 48Khz streams, and DTS-CD compatible 44.1Khz streams. I'm fairly certain some people use this encoder app for Blu-ray backup audio reencodes.

DTS's own DTS Surround Audio Suite is also exactly $249 at the moment, and has all the functionality of the SurCode app, plus support for DTS-ES Discrete and DTS 96/24 (both of which are backwards-compatible with standard DTS-capable devices/decoders). It, however, has some caveats listed on the site:

In comparing the regular DTS encoder and their DTS-HD encoder, they state the following on their FAQ page:
DTS-HD Master Audio Suite (MAS) is capable of encoding all DTS-HD™, DTS Express™, and DTS Digital Surround™ audio stream types for Blu-ray Disc™, DVD, and DTS Music Disc. DTS Surround Audio Suite (SAS) is specifically suited for standard definition optical media, such as DVD and DTS Music Disc, but cannot produce Blu-ray Disc compatible stream types
On the surface, this seems in contradiction to the answer to a question a few lines lower on the same FAQ:
Can DTS be the only audio stream on a disc?
Blu-ray Disc: Yes! Any DTS-HD Master Audio, DTS-HD High Resolution Audio™ or DTS Digital Surround stream can be the sole audio stream on the disc.
But again, lower still, we have these two answers:
Which types of DTS-HD or DTS streams are compatible with which type of optical media?
.dtshd = Blu-ray Disc (Created by MAS only)
.cpt = DVD-V, DVD-A (MAS/SAS)
.wav = DTS Music Disc (MAS/SAS)
.dts = DVD-V, DVD-A (Pro Series Encoder — discontinued)
Can I author a Blu-ray Disc with a .cpt file?
No. Blu-ray Disc does not support .the cpt file structure. Blu-ray Disc only supports the .dtshd format, which is created with the DTS-HD Master Audio Suite.
So, is DTS just trying to hard-sell the (far) more expensive suite by outright lying, or is there a grain of truth in this, such as that technically the file/format output by the less expensive software won't work with BD unless somehow tweaked? If tweaking is necessary, are there free apps to handle this? Are the files output by SurCode, on the other hand, fully ready to be loaded into a Blu-ray authoring app?

Next issue:
Does anyone have any objective/subjective comparisons on the quality of the DTS 1.5Mbps encodes of the SurCode app vs. DTS's own DVD-DTS suite, or are the algorithms in the two apps identical (and deterministic) such that any identical inputs and parameters will result in identical outputs from each app?

And finally:
Seeing as how encoding to BD-compatible 640 kbps AC3 is possible for free using Aften (eac3to) etc, can anyone here comment on subjective/objective audio differences in encodes to 1.5Mbps DTS vs 640 Kbps AC3, especially any A/B listening experiences of encodes from an identical lossless source?

Thank you all. :-)
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Old 8th January 2011, 03:32   #2  |  Link
RunningSkittle
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You dont need to re-encode or pay out the butt for this feature!

You can extract the DTS core with eac3to or other free tools. Or you could go the MKV route and choose FLAC and/or keep the DTS-HD/DTS tracks.

regarding dts vs AC3... you will find mixed opinions about which is better, warmer, accurate, more depth etc... but generally they're are about the same with AC3 taking much less bitrate.
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Old 8th January 2011, 03:57   #3  |  Link
A.Fenderson
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Thanks--I fully plan on just pulling off the core DTS track any time one is available, as that does make the most sense when it's possible.

I guess I should have clarified that I was referring to discs with multichannel LPCM or Dolby TrueHD tracks, since in the former case there may or may not be a lossy surround track at all or it may be low bitrate, and in the latter case the AC3 stream tacked onto the DD-THD stream may be encoded at a bitrate lower than the 640 kpbs max allowed for Blu-ray. Also, my target medium is BD25, so unfortunately I can't use the superior FLAC lossless compression.
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Old 8th January 2011, 05:07   #4  |  Link
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Just assembled a disc in Scenarist BD with a .cpt DTS file from a DVD project (1.5mb) which was created back in 2007 with a 'pre-HD disc' encoder.

Scenarist took it without complaint, muxed the disc, and it plays fine (in PowerDVD at least)... I'm pretty sure that DVD-encoded AC3 and DTS are 100% compatible with Blu-ray... Maybe not every authoring software is programmed to accept the .cpt file format... Other than that possibility, I can't imagine why they would say it's not compatible (other than hyping sales of the HD software...)

For AC3, I don't think I've ever seen a Blu-ray disc with less than a 640k legacy stream (not that I've looked in detail)... That would be very lame. Possible, yes, but I believe very rare...
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Old 8th January 2011, 07:39   #5  |  Link
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@rik1138: Thank you! I appreciate your effort in confirming that suspicion.
I haven't looked at my Blu-rays with an eye towards the AC3 bitrates, but I really hope you're right, since I get the impression that 640k AC3 and 1.5M DTS are both generally considered perceptually near-lossless. I'd like to meet that goal without having to purchase additional software.
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Old 8th January 2011, 11:03   #6  |  Link
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Originally Posted by A.Fenderson View Post
It seems like some people who likely find DTS 1.5Mbps a sweet-spot for quality vs. bitrate for surround-encoding are reencoding some of their lossless BD audio tracks to core DTS for their backups using BD-RB, or going to MKV, etc. I am considering this route myself (generally to BD25 via BD-RB), but have some questions for those in the know.
People doing this generally do this because they want to play the rips on mediatanks or mediastreamer or or or (fill in the names yourself). Except for several notable exceptions, and which are by far extremely expensive*, none of them can use lossless HD audio, not even as bitstream, otherwise they would be forced to pay licence fees which would raise the end price (bye bye 60€ mediaplayer-that-plays-everything).

Even those playing it on a PC still have to fight several hurdles in order to get lossless HD audio digitally out (the cheapest audio card with HDMI or video card with HDMI-audio is ~300€, 2-3x the price of an entry level BD player).

5.1 is the easiest way of having high quality audio, without too much trouble.

So they are generally forced to do this, it's not their choice as you thought it were.

* Popcorn Hour, some models, at least 350€ bare
HD Dune, some models, at least 500€
Sony PS3, at least 300€, cinavied

vs

WD TV ~ 80€
China-noname ~ 60-100€ (according to the rebadger)
even some entry level USB-enabled BD players (lots of restrictions though) ~ 100-150€
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Old 8th January 2011, 13:00   #7  |  Link
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Originally Posted by A.Fenderson View Post
@rik1138: Thank you! I appreciate your effort in confirming that suspicion.
I haven't looked at my Blu-rays with an eye towards the AC3 bitrates, but I really hope you're right, since I get the impression that 640k AC3 and 1.5M DTS are both generally considered perceptually near-lossless. I'd like to meet that goal without having to purchase additional software.
I also would agree with what others have said - if there's a 640 AC3 or full rate DTS track available then just use them.

As rik1138 said there are some rare examples where this isn't the case (LPCM / TrueHD with <640 AC3 or DTS-HD with a half rate core) but they're so few and far between that (IMO) it's not worth shelling out money in order to transcode. I'd just live with the lower rate, or if you do transcode then use a free solution such as Aften. No point in worrying about it anyway until you actually find a disk where this is the case
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Old 8th January 2011, 17:17   #8  |  Link
nurbs
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So they are generally forced to do this, it's not their choice as you thought it were.
I think saying that people are generally forced to use lossy tracks is quite a stretch.
A lossless track is much bigger, less compatible and people are often unable to distinguish between that and a high bitrate encode (e.g. AC3 640 kbps).
I have a WD TV and while it would be nice if it supported more formats like DTS-HD I'd never use that functionality.
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Old 8th January 2011, 18:49   #9  |  Link
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I think saying that people are generally forced to use lossy tracks is quite a stretch.
A lossless track is much bigger, less compatible and people are often unable to distinguish between that and a high bitrate encode (e.g. AC3 640 kbps).
I have a WD TV and while it would be nice if it supported more formats like DTS-HD I'd never use that functionality.
See, what use a format that cannot be used in practice

The lossless HD audio both on mediaplayers and PC is extremely cumbersome, even if converted into FLAC. The only feasable way of using lossless HD audio is to burn it on a BD video (along with the video track to whom it belongs) and play it on standalones (hopefully not "cinavied").

So, people are forced to use 5.1 lossy because of:
1. the available space
2. multiple issues with HD lossless on PC
3. unsupported format on most mediaplayers

Both this post and the other one should be understood as "no, people do not reencode to lossy", but as "people keep the lossy", not only because the access to 6 true channels is beyond the monetary reach of a consumer, but also because 6 chn. encoding software play in the same league.
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Old 8th January 2011, 19:04   #10  |  Link
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Originally Posted by rik1138 View Post
For AC3, I don't think I've ever seen a Blu-ray disc with less than a 640k legacy stream (not that I've looked in detail)... That would be very lame. Possible, yes, but I believe very rare...
There are more of them than you know. The two worst studio offenders are Sony (Casino Royale [all versions] is one example) and Warner (most of the Kubrick collection and many others).
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Old 9th January 2011, 13:26   #11  |  Link
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Not sure if you have stumbled across this link or not, but it's an interesting study done by European broadcasters (the pretty graphs start on page 21!):
http://tech.ebu.ch/webdav/site/tech/...h/tech3324.pdf

For those too lazy to click the link, basically the "Original ANC", "DTS 1500" and "DD+ 448" (AC3 640kbps) tracks all score 92-95% on the perceived quality score (so the lossless formats should score the same as "ANC_Original"!) ...

7ek
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Old 10th January 2011, 21:58   #12  |  Link
rik1138
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There are more of them than you know. The two worst studio offenders are Sony (Casino Royale [all versions] is one example) and Warner (most of the Kubrick collection and many others).
I can also imagine some studios might try to use the already-created AC3 for DVD as the legacy stream just to save the minutes of time required to re-encode it... Even though the Dolby encoder will do both THD and the legacy at the same time (or at least in the same queue).

They wouldn't go above 448 for DVD, so I guess that can be a problem with older titles. Hopefully even that practice (if it existed) is being phased out...
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Old 10th January 2011, 22:53   #13  |  Link
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Even those playing it on a PC still have to fight several hurdles in order to get lossless HD audio digitally out (the cheapest audio card with HDMI or video card with HDMI-audio is ~300€, 2-3x the price of an entry level BD player).
Every AMD HD 5XXX/6XXX video card can output HD audio formats including bitstreaming DTS Master Audio and Dolby TrueHD. The cheapest ones goes for $40 CAD here.

http://www.newegg.ca/Product/Product...-358-_-Product
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Old 11th January 2011, 00:32   #14  |  Link
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I also would agree with what others have said - if there's a 640 AC3 or full rate DTS track available then just use them.

As rik1138 said there are some rare examples where this isn't the case (LPCM / TrueHD with <640 AC3 or DTS-HD with a half rate core) but they're so few and far between that (IMO) it's not worth shelling out money in order to transcode. I'd just live with the lower rate, or if you do transcode then use a free solution such as Aften. No point in worrying about it anyway until you actually find a disk where this is the case
I had incorrectly assumed that the DTS core+extension model wouldn't bother to accomodate anything other than a full-rate core, but according to this DTS document (.pdf), they can be half-rate, or, under certain circumstances, several other rates between half and full. Kinda counter-intuitive, IMO, since you're presumably just shifting the quality you're trying to achieve/surpass from the core to the extension, but then again maybe the extension codecs are that much more efficient than the core that it saves overall space at the same perceptual quality level when decoding the HD stream--I just wish it weren't done at the expense of the quality of the more compatible core stream.

Quote:
Originally Posted by 7ekno View Post
Not sure if you have stumbled across this link or not, but it's an interesting study done by European broadcasters (the pretty graphs start on page 21!):
http://tech.ebu.ch/webdav/site/tech/...h/tech3324.pdf

For those too lazy to click the link, basically the "Original ANC", "DTS 1500" and "DD+ 448" (AC3 640kbps) tracks all score 92-95% on the perceived quality score (so the lossless formats should score the same as "ANC_Original"!) ...

7ek
Thanks for the link, that's good info. Unfortunately, they didn't seem to use actual standard AC3 @ 640kbps, and I'm not sure you can equate DD+ @ 448 with AC3 @ 640. It would have been cool if they'd tested 768 kbps DTS in the mix as well.

A few more questions come to mind:

* Has anyone here bothered using Aften/eac3to to reencode to AC3@640 for similar reasons, and if so did the resulting file sound more transparent to the high-def/lossless source than did the (presumably) low-bitrate compatibility track that had been used alongside/within the HD/lossless?

* Has anyone ever had any compatibility problem with Aften-encoded AC3 tracks (via BD-RB/eac3to etc) on hardware decoders (BD player, HT receiver)?

* Are BD players set to bitstream via SPDIF actually streaming 640kbps AC3 tracks at full bitrate, or stripping it down to 448 somehow for compatibility with older receivers, seeing as how until BD/HD-DVD, no consumer devices I'm aware of really output 640 kbps AC3? Has anyone ever happened across an older DD/AC3 receiver that didn't support/function with bitstreamed 640 kbps AC3?
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Old 11th January 2011, 03:01   #15  |  Link
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* Are BD players set to bitstream via SPDIF actually streaming 640kbps AC3 tracks at full bitrate, or stripping it down to 448 somehow for compatibility with older receivers, seeing as how until BD/HD-DVD, no consumer devices I'm aware of really output 640 kbps AC3? Has anyone ever happened across an older DD/AC3 receiver that didn't support/function with bitstreamed 640 kbps AC3?
They'll output at 640kbps. Prior to BD / HD DVD other equipment did this, such as the original Xbox (coming up to its 10th birthday this year).
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Old 11th January 2011, 03:18   #16  |  Link
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They'll output at 640kbps. Prior to BD / HD DVD other equipment did this, such as the original Xbox (coming up to its 10th birthday this year).
Interesting. So presumably decoding ability for 640 Kbps has been mandated for DD logo-displaying receivers from the beginning?
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Old 11th January 2011, 06:44   #17  |  Link
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People doing this generally do this because
Even those playing it on a PC still have to fight several hurdles in order to get lossless HD audio digitally out (the cheapest audio card with HDMI or video card with HDMI-audio is ~300€, 2-3x the price of an entry level BD player).
woah, hold up. the cheapest video card is the radeon 5450, and that goes for like $30-$40, the cheapest video card that can do lossless hdmi audio and 3d video is the nvidia gt 430, and that is like $70-$80.
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Old 11th January 2011, 07:47   #18  |  Link
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Originally Posted by A.Fenderson View Post
Interesting. So presumably decoding ability for 640 Kbps has been mandated for DD logo-displaying receivers from the beginning?
Yes. 640 kbps has always been part of the AC-3 spec for receivers, even back when all there was were 384 kbps tracks on laserdiscs.
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Old 11th January 2011, 08:31   #19  |  Link
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woah, hold up. the cheapest video card is the radeon 5450, and that goes for like $30-$40, the cheapest video card that can do lossless hdmi audio and 3d video is the nvidia gt 430, and that is like $70-$80.
In the US maybe
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Old 11th January 2011, 09:35   #20  |  Link
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In the US maybe
This Dutch site sells the HD5450 for 32 Euros.

http://www.komplett.nl/Komplett/prod...Z/default.aspx
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