What's wrong with TrueHD?!?

[werewuf]

Originally Posted by quetzalcoatl

On this board you might just need to have a flame retardant computer with a statement like this.

Than do as I have: Do the research. Call DTS and ask to speak to a tech and ask him. Make friends with your local Pioneer rep and over five months ask a zillion questions about your new equipment and upgrade from one player to the next and one receiver to the next. Call Dolby and speak to a tech and ask.(this I haven't done) However, there would be no point to THD or HDMA if it was all just PCM.

[HDJK]

Originally Posted by werewuf

However, there would be no point to THD or HDMA if it was all just PCM.

O.k., I fold. At this point I don't see a reason to continue this little chat. I'm just glad that you're happy with your new player. I guess that's all that matters...

[HDBlu]

Hmmm. The original soundtrack master for Spiderman 3 is 24-bit/48 khz.

The PCM track on the Blu-ray is down ressed to 16-bit.

The TrueHD track is a losslessly compressed encode of the original, also at 24-bit resolution.

Mr. Boulet claims the 16-bit version sounds better.

But he is listening to a 2-channel down mix.

Someone please que the caveman...

[Frode]

Originally Posted by DaViD Boulet

But are you sure that this is how the PS3 is doing it?

No, I'm not sure for the PS3, since it's all software. I can easily see it being different on a standalone deck since the downmixing can then be done with a decoder that's separate from the main mixer. Maybe kjack can chime in on how they do it for their solutions.

It's possible that they used a "cheaper" downmixing algorithm for THD on the PS3 compared to PCM, in order save CPU cycles. Mixing methods can affect volume levels depending on how the audio streams are matrixed back together.

[Tok]

Originally Posted by Frode

No, I'm not sure for the PS3, since it's all software. I can easily see it being different on a standalone deck since the downmixing can then be done with a decoder that's separate from the main mixer. Maybe kjack can chime in on how they do it for their solutions.

It's possible that they used a "cheaper" downmixing algorithm for THD on the PS3 compared to PCM, in order save CPU cycles. Mixing methods can affect volume levels depending on how the audio streams are matrixed back together.

Don't all TrueHD title have a secret lossy DD track along with them for people without HDMI capable receivers. Maybe the PS3 is decoding the lossy track when it is set to downmix? I have a feeling when a PS3 user is connected with the old optical connection it only sends the lossy track when TrueHD is selected since it assumes the end user only has equipment capable of lossy multi-channel or 2.0 PCM.

[Frode]

Player (to PCM, not the backup DD track) vs receiver decoding of THD:

The difference is that if you bitstream the THD track to the receiver you can "take advantage" of features such as midnight mode/dynamic range compression. That kind of metadata isn't transmitted with PCM.

[LembasBread]

Originally Posted by werewuf

However, there would be no point to THD or HDMA if it was all just PCM.

There is: to have the same quality of a LPCM track in a smaller space. They are lossless compressions of LPCM mixes. D to A converters convert LPCM to electrical waveforms, not TrueHD/DTS-HD MA to electrical waveforms.

The "proprietary decoding" means that to decode TrueHD, only a TrueHD decoder can extract the encoded info. There isn't a special mixing technique that takes place when compressing for TrueHD and DTS-HD MA. It's simply the LPCM video master being compressed. So on The Fifth Element, audible differences w/ the TrueHD being superior are a little suspect. Paidgeek has stated that the TrueHD and LPCM tracks for that title are compressed from the same 16-bit master; they're exact same audio, one is just zip compressed in a TrueHD track. The TrueHD on 5th Element should be exactly identical to the LPCM and not superior barring any extra processing being done.

[Frode]

Good point Craig. You might be on to something there.

[LembasBread]

Originally Posted by dobyblue

Another compelling reason for more DTS-HD Master Audio mixes as all reports of users now able to listen to the DTS-MA mixes are nothing short of absolutely bloody stunning.

Unfortunately, there aren't any titles that have both a DTS-HD MA and an LPCM track to compare it to.

[DaViD Boulet]

Paidgeek,

I certainly will try to track down an HDMI receiver... but no one I know has one (my "high end" friend's lexicon only handles SPDIF). Maybe I can bring my PS3 to a dealer and hear a direct-HDMI 5.1 PCM audition there.

Yes, please help with the PS3 research. If it turns out that there *is* a difference in the down-mixing in the player, then naturally I'll make every effort to correct my review and get the appropriate gear ASAP. However, I'd be baffled if the "downmixing", even by a Dolby chip, would reduce amplitude in the process. If so, then Dolby *still* deserves to be raked over the coals for such a bad downmixing algorithm (though that would leave the soundtrack on the disc blame-free).

NOTE to everyone interested in this topic: the Dolby chip has, and has *always* had, a 5.1-2.0 dowmixing feature. This is nothing new (it's how you can have a stereo output on the back of your DVD player). However, I would be very surprised if the PS3 is using that particular algorithm of the chip for downmixing for SPDIF after extraction of TrueHD to PCM given that it already downmixes PCM to 2.0 on its own, but anthing is possible!

[DaViD Boulet]

Don't all TrueHD title have a secret lossy DD track along with them for people without HDMI capable receivers. Maybe the PS3 is decoding the lossy track when it is set to downmix? I have a feeling when a PS3 user is connected with the old optical connection it only sends the lossy track when TrueHD is selected since it assumes the end user only has equipment capable of lossy multi-channel or 2.0 PCM.

Under normal circumstances the PS3 does what you describe.

In order to get the extracted lossless audio from the TrueHD out the SPDIF output (and not the lossy "core" stream), you have to tell your PS3 to disable DD output and only output PCM. It then decodes the TrueHD to 5.1 PCM internally, downmixes to 2.0, and outputs via SPDIF... at least according to what's been reported at AVS in the PS3 threads!

Hmmm. The original soundtrack master for Spiderman 3 is 24-bit/48 khz.

The PCM track on the Blu-ray is down ressed to 16-bit.

The TrueHD track is a losslessly compressed encode of the original, also at 24-bit resolution.

Mr. Boulet claims the 16-bit version sounds better.

But he is listening to a 2-channel down mix.

Someone please que the caveman...

Listening to a 2.0 downmix of *both* signals (the LPCM and the extracted TrueHD). *should* still be an apples-apples comparison, unless it does turn out a different algorithm is downmixing each signal. Note that Greg at thebits heard the same thing that I'm hearing (pcm sounding better).

[DaViD Boulet]

Than do as I have: Do the research. Call DTS and ask to speak to a tech and ask him. Make friends with your local Pioneer rep and over five months ask a zillion questions about your new equipment and upgrade from one player to the next and one receiver to the next. Call Dolby and speak to a tech and ask.(this I haven't done) However, there would be no point to THD or HDMA if it was all just PCM.

Your contact is slightly misinformed. Sure, the encoding/decoding algorithms are "proprietary". But that's like saying that the algirithm used by win-Zip is "propreitary". They own it. But all it does is take a file, "zip it" with propretary software, and then unzip it later with propriety software back to its original bit-for-bit file.

That's what Dolby TrueHD and DTS-HD MA are supposed to do too... compress a PCM signal "losslessly" and the unzip it back to the original bit-for-bit PCM original.

The only reason DTS-HD MA and TrueHD are being used is that they offer an advantage in storage space on the BD and HD DVD discs... the "zipped" PCM files take about 1/2 the space than the "flat" or linear PCM.

[Tok]

Originally Posted by DaViD Boulet

Under normal circumstances the PS3 does what you describe.

In order to get the extracted lossless audio from the TrueHD out the SPDIF output (and not the lossy "core" stream), you have to tell your PS3 to disable DD output and only output PCM. It then decodes the TrueHD to 5.1 PCM internally, downmixes to 2.0, and outputs via SPDIF... at least according to what's been reported at AVS in the PS3 threads!

I would not put to much faith into what anyone claims on the forums. The only way to know for sure is to have a PS3 engineer detail the audio codecs and their possible signal paths.

I still think if you are hearing a very significant difference it may be related to the lossy vs. lossless tracks. I completely agree with you that DN should not even be an option on encoders that are intended for prerecorded media. Dolby should not have it on by default.

I have a HDMI system with an Onkyo 805 and PS3. I have a pretty nice DefTech speaker system (BP10Bs, CLR2000, BP2xS, PM100MKIIs and a Velodyne CT100) I will be sure to do some comparisons tomorrow after I pick it up. Any timeframes I should look for where the differences are readily apparent?

[dobyblue]

Originally Posted by LembasBread

Unfortunately, there aren't any titles that have both a DTS-HD MA and an LPCM track to compare it to.

Bruce Almighty from the UK has DTS-MA and PCM, but one is Spanish and one is English.

[werewuf]

Originally Posted by DaViD Boulet

Your contact is slightly misinformed. Sure, the encoding/decoding algorithms are "proprietary". But that's like saying that the algirithm used by win-Zip is "propreitary". They own it. But all it does is take a file, "zip it" with propretary software, and then unzip it later with propriety software back to its original bit-for-bit file.

That's what Dolby TrueHD and DTS-HD MA are supposed to do too... compress a PCM signal "losslessly" and the unzip it back to the original bit-for-bit PCM original.

The only reason DTS-HD MA and TrueHD are being used is that they offer an advantage in storage space on the BD and HD DVD discs... the "zipped" PCM files take about 1/2 the space than the "flat" or linear PCM.

That's what you want it to be. It is not. If that was the case no one would bother with the new players or receivers, there would be no product to sell.

[DaViD Boulet]

werewuf,

stop before you hurt yourself buddy. you're talking tech-talk without a grasp on what's really going on. Sure, there are bells and whistles to new products. However, the decoding priciples behind a lossless algorithm are what they are... you're extracting a datafile. Dolby and DTS both agree with this. There are plenty of reasons to buy new products without having to change the principles behind unzipping a lossless datafile.

In fact, it's this abiltiy to zip lossless and get back bit-for-bit accuracy with these two new codecs that is the reason they were included on HD media and are now appearing in decoding hardware.

[DaViD Boulet]

I would not put to much faith into what anyone claims on the forums. The only way to know for sure is to have a PS3 engineer detail the audio codecs and their possible signal paths.

I believe that confirmation from a reliable source was obtained. Hopefully Paidgeek can get back with some clarification once he hears from the techs at Sony.

I have a HDMI system with an Onkyo 805 and PS3. I have a pretty nice DefTech speaker system (BP10Bs, CLR2000, BP2xS, PM100MKIIs and a Velodyne CT100) I will be sure to do some comparisons tomorrow after I pick it up. Any timeframes I should look for where the differences are readily apparent?

I noticed differences throughout the entire film. However, scenes with music, like when Mary Jane is singing on stage, were particularly clear. Music sounded "dumbed down" on the TrueHD in comparison to the PCM.

[Frode]

Originally Posted by werewuf

That's what you want it to be. It is not. If that was the case no one would bother with the new players or receivers, there would be no product to sell.

Can you point out in the THD or DTS-MA specs where it says that the output is different from the original PCM? Heck, even the whitepapers should be enough .

[gandley]

Originally Posted by werewuf

That's what you want it to be. It is not. If that was the case no one would bother with the new players or receivers, there would be no product to sell.

Im not getting that at all.

PCM is not very effiecent, so Dolby and DTS have come up with a way to store PCM with more compression to save space. i guess you have heard of MLP lossless audio which we now know as true HD

Meridian Lossless packaging is a lossless coding system for high quality linear PCM, thats right its just a repackaging system for linear PCM

[gandley]

Unlike perceptual or lossy data reduction, lossless coding does not alter the final decoded signal in any way, but merely ‘packs’ the audio data more efficiently into a smaller data rate for transmission.

MLP is a simple-to-decode method optimised for the new requirements brought about by applications like DVD Audio, and in particular has been optimized to enable more opportunities for multichannel and for audio at high sample rates with high precision

MLP is an audio coding scheme that discovers the redundancy and packs the audio into a smaller space – but in such a way that a simple decoder can recover the original signal exactly bit-for- bit.

more info

http://www.meridian-audio.com/w_paper/mlp_jap_new.PDF