What's wrong with TrueHD?!?

[DaViD Boulet]

What's wrong with the Dolby TrueHD on SpiderMan 3 Blu-ray???

In my review at dvdfile.com, I notice a definite compromise with the sound of the TrueHD compared to the PCM on Spiderman 3.

http://www.dvdfile.com/index.php?opt...=6337&Itemid=3

But I did discover something that concerns me greatly that the studios need to address and correct NOW early in life of TrueHD software: when I compared the PCM uncompressed 5.1 track to the Dolby TrueHD track on the third disc (which contains both types of lossless audio), despite the theory that the two audio tracks should sound identical, the PCM track was audibly superior to the TrueHD and I didn’t have to struggle to hear the difference… it was obvious. The PCM track was more robust, textured, realistic, and also seemed louder (I level-compensated when comparing to make sure I wasn’t being biased by mere level differences). As good as it was, by comparison the Dolby TrueHD track sounded slightly restrained, and “smoothed over”. My suspicion (even though Sony as stated they do not set the dialog normalization flag to engage processing) is that this slightly compromised fidelity of the Dolby TrueHD track is a result of dialogue normalization processing which is applied after the lossless sound file is extracted in the playback hardware’s decoding engine, and effectively re-writes every bit word with a new value as the amplitude of the entire digital waveform is digitally recalculated/reduced. I should point out that my audio gear, while better than the average Circuit-City rack-system, isn’t comprised of out-of-reach esoteric gear; I’m confident that most critical listeners with “good” sound systems will be able to hear the difference between the Dolby TrueHD and PCM soundtrack on the third film without difficulty. Sony and other studios: PLEASE learn how to properly optimize Dolby TrueHD so that it sounds 100% identical to the PCM original.

Greg from thedigitalbits notices the same thing:
http://www.thedigitalbits.com/review...eviews009.html

The audio is no less disappointing. Encoded with both Dolby TrueHD and linear PCM tracks, Spider-Man 3 on Blu-ray is a breathtaking aural experience. The entire soundstage is used to full effect with clear dialog, pounding low frequencies and split-surround effects. Between the two high-end soundtracks, the linear PCM track is the preferred choice. Differences are slight, but there are differences nonetheless. The Dolby version has a slightly more plugged-up sound when compared with the airier, more transparent PCM track. This is likely due to the lower, variable bit-rate of the Dolby technology compared with the higher, fixed bit-rate of PCM. Again, these are not differences that slap you in face, but they're enough to notice.

Ok, so what's going on? Paidgeek, I'm almost 100% convinced that Dialogue Normalization *has* been applied to these TrueHD tracks. When your audio engineers told you that they wouldn't do it, were they aware that the equipment does it by default and that if they didn't want DN applied they'd have to manually reset the flag to -31?

I'm sure that the same problem exists with the TrueHD tracks on the other discs, but without the PCM to compare the compromise isn't as apparent (true for probably every TrueHD encoding out there on either format).

Help us. What's wrong? DolbyTrueHD won't be "lossless" until it's 100% transparent to the PCM original. Nothing less will do.

[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.

[DaViD Boulet]

Hey, fill me in. Who's able to get full DTS-MA decoding? Any links? Equipment?

[GoldenRedux]

Originally Posted by DaViD Boulet

Hey, fill me in. Who's able to get full DTS-MA decoding? Any links? Equipment?

Onkyo 705, 805 and 905 AVRs all decode DTS-HD MA. The Samsung P1400 streams DTS-HD MA, and I believe the latest Pioneer ELITE BD player does as well (can't remember the model number right now). There are other AVRs also from Yamaha, Denon, and Sony, currently or soon to be available that also decode DTS-HD MA.

[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.

[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.

[paidgeek]

Originally Posted by DaViD Boulet

What's wrong with the Dolby TrueHD on SpiderMan 3 Blu-ray???

In my review at dvdfile.com, I notice a definite compromise with the sound of the TrueHD compared to the PCM on Spiderman 3.

http://www.dvdfile.com/index.php?opt...=6337&Itemid=3



Greg from thedigitalbits notices the same thing:
http://www.thedigitalbits.com/review...eviews009.html






Ok, so what's going on? Paidgeek, I'm almost 100% convinced that Dialogue Normalization *has* been applied to these TrueHD tracks. When your audio engineers told you that they wouldn't do it, were they aware that the equipment does it by default and that if they didn't want DN applied they'd have to manually reset the flag to -31?

I'm sure that the same problem exists with the TrueHD tracks on the other discs, but without the PCM to compare the compromise isn't as apparent (true for probably every TrueHD encoding out there on either format).

Help us. What's wrong? DolbyTrueHD won't be "lossless" until it's 100% transparent to the PCM original. Nothing less will do.

David, can you tell me what equipment you are using and how you have it connected?

[DaViD Boulet]

At home I have a PS3 and a B&K AVR 212 that lacks HDMI. So I set my PS3 to "PCM output" which causes it to decoded the TrueHD into PCM (in theory, bit-for-bit matching the PCM original). Then the PS3 folks the 5.1 into 2.0 for both the decoded trueHD streat and the linear PCM sountrack for transmission over SPDIF.

Naturally, downmixing to 2.0 isn't ideal in regards to the original 5.1 mix. However, let me stress that this wouldn't affect a comparison between the TrueHD and LPCM soundtrack as the same 2.0 downmixing is being applied to both. If they were bit-for-bit mirrors of each other in 5.1 PCM mode (after decoding the TrueHD to PCM), they'd sound 100% idential to each other even when downmixed to 2.0.

They don't. The PCM still sounds louder, more robutst, and more nuanced/revealing with considerably more "air" and atmosphere.

Sounds like the classic case of DN applied to the DD tracks. Anyone have equipment to confirm??? Paidgeek, what do your audio engineers have to say? Are they still convinced they applied no DN? Are they aware that their Dolby encoder applied DN to EVERY signal it encodes by default unless it is manually overridden each time? Why is the playback level so much softer than the PCM track? Digital audio signals just don't reduce amplitude on their own.

[werewuf]

I have the new Pioneer BDP-95FD and VSX-94TXH. On comparing True HD to PCM on the Fifth Element soundtrack I found the exact opposite to be true (no pun intended) The opening of the movie, which has ambient space music is much more robust and exciting. Also, during early scenes in the chamber where President Lindberg is conducting his the interview with Father Vito Cornelius, on the PCM track there is chattering in the background, with the True HD version you can understand what they are saying.......
Quite honestly, IMHO, until you have the capability to play True HD with the right equipment you cannot compare. Also, I had the BDP-94HD previously which could not bitstream True HD to my receiver, when I inquired with the local Pioneer rep, (and he consulted with his higher ups) he said that with the 94 it converted True HD to PCM which meant you are not getting the full signal do to conversion.

[TauRus]

Originally Posted by DaViD Boulet

... Naturally, downmixing to 2.0 isn't ideal in regards to the original 5.1 mix. However, let me stress that this wouldn't affect a comparison between the TrueHD and LPCM soundtrack as the same 2.0 downmixing is being applied to both...

David, I think you are making some serious assumptions here, I am not sure that downmixing is processed the same way and therefore yields the same results on these two very different technologies. I am no expert, just have doubts these assumptions are accurate.

[NutsAboutPS3]

Surely it is easy to see if it is lossless or not with the following test?
1. Take a PCM file.
2. Encode it to TrueHD
3. Decode it back to PCM.
4. Diff the two PCM files - they are either identical, or they aren't.

If I were producing Blu-ray discs with TrueHD tracks as part of my job, steps 3 and 4 would be part of my standard process to verify that an error hadn't occurred.

[DaViD Boulet]

Taurus,

If the Dolby TrueHD decoded to a bit-for-bit replica of the 5.1 PCM, then downmixing the two to 2.0 would still produce two identical digital files.

The downmixing happens after the TrueHD is extracted to PCM.

(edit)

Also, I had the BDP-94HD previously which could not bitstream True HD to my receiver, when I inquired with the local Pioneer rep, (and he consulted with his higher ups) he said that with the 94 it converted True HD to PCM which meant you are not getting the full signal do to conversion.

Extraction to PCM doesn't lose anything from the TrueHD because that's what the TrueHD is compressing. You may not be fully understanding what TrueHD is (or is supposed to be). It's basically a "zip file" for a PCM file. In other words, it's supposed to get "extracted" back to PCM... because that's what it's zipping (actually, all compressed signals, both lossy and lossless, get extracted back to PCM before d/a conversion). The only issue in the case of playback is whether your player unzips it or your receiver/decoder unzips it. HDMI 1.3 means you can send the raw TrueHD signal to your decoder for extraction to PCM there. Aside from jitter issues, there should be no difference if one device unzips or another devics unzips... unless there's additional DSP that one device applies that another does not.

Dialog Normalization is an example of DSP that's applied to a TrueHD stream *after* decoding back to PCM. It's not defeatable in consumer gear, and both players and decoders are forced to apply it if the flag is set.

[werewuf]

Hmmm. You can hear "chattering in the background" with the PCM but not the TrueHD? Sounds like the TrueHD is missing audible ambient information.[/QUOTE]

What I meant was the True HD was superior because it was no longer chattering but understandable dialog. Also, I had the BDP-94HD previously which could not bitstream True HD to my receiver, when I inquired with the local Pioneer rep, (and he consulted with his higher ups) he said that with the 94 it converted True HD to PCM which meant you are not getting the full signal do to conversion.

[owa]

Originally Posted by DaViD Boulet

Hmmm. You can hear "chattering in the background" with the PCM but not the TrueHD? Sounds like the TrueHD is missing audible ambient information.

I took it to mean he was saying the TrueHD version sounded clearer. That is, with PCM it sounded like chatter he couldn't make out but with the TrueHD version, he could understand what they were saying. I could be wrong but that's how I interpreted his comment.

Edit: Nevermind, he replied.

[werewuf]

Originally Posted by DaViD Boulet

Extraction to PCM doesn't lose anything from the TrueHD because that's what the TrueHD is compressing. You may not be fully understanding what TrueHD is (or is supposed to be). It's basically a "zip file" for a PCM file. In other words, it's supposed to get "extracted" back to PCM... because that's what it's zipping (actually, all compressed signals, both lossy and lossless, get extracted back to PCM before d/a conversion). The only issue in the case of playback is whether your player unzips it or your receiver/decoder unzips it. HDMI 1.3 means you can send the raw TrueHD signal to your decoder for extraction to PCM there. Aside from jitter issues, there should be no difference if one device unzips or another devics unzips... unless there's additional DSP that one device applies that another does not.

Dialog Normalization is an example of DSP that's applied to a TrueHD stream *after* decoding back to PCM. It's not defeatable in consumer gear, and both players and decoders are forced to apply it if the flag is set.

First, I am not Taurus, but Werewuf. The way it has been explained to me is that True HD and DTS HDMA decoding is proprietary. I have spoken to a tech at DTS and his explanation was that until you had the proper decoders your not going to get their new product completely. When I had my BDP-94 I noticed the same difference that you stated, PCM was more robust. Now that I have the 95 and my receiver is showing True HD or HDMA what I am hearing now is vastly superior in all respects.

[Frode]

Downmixing TrueHD to stereo is a feature that's handled by the DD decoder (it's in the spec on how to do it), while downmixing to PCM is handled by the system itself.

http://www.dolby.com/assets/pdf/tech...whitepaper.pdf

What you're hearing is probably a result of that, rather than DN. This makes me wonder how many other reviewers out there are essentially using stereo setups to listen to 5.1 lossless tracks.

[paidgeek]

Originally Posted by DaViD Boulet

At home I have a PS3 and a B&K AVR 212 that lacks HDMI. So I set my PS3 to "PCM output" which causes it to decoded the TrueHD into PCM (in theory, bit-for-bit matching the PCM original). Then the PS3 folks the 5.1 into 2.0 for both the decoded trueHD streat and the linear PCM sountrack for transmission over SPDIF.

Naturally, downmixing to 2.0 isn't ideal in regards to the original 5.1 mix. However, let me stress that this wouldn't affect a comparison between the TrueHD and LPCM soundtrack as the same 2.0 downmixing is being applied to both. If they were bit-for-bit mirrors of each other in 5.1 PCM mode (after decoding the TrueHD to PCM), they'd sound 100% idential to each other even when downmixed to 2.0.

They don't. The PCM still sounds louder, more robutst, and more nuanced/revealing with considerably more "air" and atmosphere.

Sounds like the classic case of DN applied to the DD tracks. Anyone have equipment to confirm??? Paidgeek, what do your audio engineers have to say? Are they still convinced they applied no DN? Are they aware that their Dolby encoder applied DN to EVERY signal it encodes by default unless it is manually overridden each time? Why is the playback level so much softer than the PCM track? Digital audio signals just don't reduce amplitude on their own.

David,

I will do some research on how the PS3 manages downmixes that are PCM or decoded Dolby, but this will take a while. I strongly suspect that there are differences in how the two file types are handled and this is what you are hearing. Can I ask that you try repeating your test with a borrowed HDMI reciever or on a friends trusted system in full 5.1?