Dolby improves the sound of Bluray...sort of

[Sir Terrence the Terrible]

On Friday evening I had the opportunity to visit Dolby Labs to hear their newest technology Dolby Atmos, and Dolby TrueHD 96k. This is my second time hearing Dolby Atmos 13.1 for the professional theaters, so I was much more interested in Dolby TrueHD 96k.

Just a background on TrueHD 96k, what Dolby does is upsample the 48khz sample rate of Bluray soundtracks to 96khz during encoding. The reason it is done this way, is because using a native 96khz sample rate for encoding takes up a lot of disc space which could effect video quality. By upsampling during encoding, not much additional space is taken up on the disc, which means nothing is taken from the bit rate of the video. By upsampling to 96khz, the anti aliasing filters have more gentle roll off the falls at 48khz, and eliminates the brickwall filters at 24khz. Dolby has liscensed Meridians Digital Audio new "Apodizing" filter which reduces an effect call pre-ringing which is supposed to give the audio more clarity. Pre-ringing causes digital audio to sound hard and harsh, and this filter reduces and even eliminates that harshness and hardness - making the audio sound more clear and natural. At least that are the claims.

Dolby's company theaters are the best in the business, second only to Disney's and Sony screening and home theater rooms. The system is top notch, and extremely well calibrated, so I was really looking forward to this.

Some clips were loaded on a computer, and these clips include 'The Lost Bladesmen', 'The Dark Knight', 'Kung Fu Panda', 'Flowers of War'. I was also given a Bluray disc of the San Francisco Orchestra at 100, a disc that commemorates the Orchestra's 100 year anniversary.

In previous demonstrations, the Dolby guys told the listeners what to listen for, and there were visual cues when the upsampling filter was on and off. I asked if they would not do this, as I know the power of suggestion, and how one can be manipulated into hearing something they might not otherwise notice,
With that, the lights went down, and the demo began.

Was Dolby demo a success? Well sort of. All of the clips sound really good, and I mean really good. However, the difference between the upsampled sound, and the standard sample clips was so subtle I could barely detect the difference. Sometimes I could not hear any difference at all! The upsampling process did not harm, but I am not sure it did that much good either. Consider me a skeptic on this one. Perhaps in a smaller room where we are closer to the speakers, I will hear a difference. I am willing to give this technology another chance under different conditions.

[Woochifer]

Count me among the skeptics on this one. Sounds like a nice refinement, but hardly anything that will make or break the sound quality. I'm all for higher res audio, and bringing the data streams as close as possible to the master source. But, upsampling a 48 kHz signal to 96 kHz is not the same thing as the real thing.

I understand the need to conserve disc space, especially with video content taking priority, but doesn't DTS HD Master Audio already encode the audio at 96/24 resolution?

[Feanor]

Thanks for the update, Sir T. But I'm a bit confused.

I'm wondering though if Dolby TrueHD is sometimes recorded at a native 96 kpbs?

According to Wikipedia, (here) (http://en.wikipedia.org/wiki/Blu-ray_Disc#Audio), Blu-ray supports Dolby TrueHD (lossless) at up to 24/96 for 8 channels or 24/192 for 5 channels. But is are these the non-upsampled rates? And if our players report 24/96 is there any way to know if this is native or upsampled?

[Sir Terrence the Terrible]

Count me among the skeptics on this one. Sounds like a nice refinement, but hardly anything that will make or break the sound quality. I'm all for higher res audio, and bringing the data streams as close as possible to the master source. But, upsampling a 48 kHz signal to 96 kHz is not the same thing as the real thing.

I understand the need to conserve disc space, especially with video content taking priority, but doesn't DTS HD Master Audio already encode the audio at 96/24 resolution?

All Bluray soundtracks are sampled at 48khz. Here is what I suspect. Dolby TrueHD is basically disappearing off the Bluray format in favor of Dts HD Master audio. This is a chance for Dolby to reverse this trend by market differentiation - or to leave the impression that somehow Dolby TrueHD is a better codec than Dts's using this process. They make the claim that this process of upsampling will make TrueHD sound better than the master file itself via the Apodizing filter inserted in the encoding process during upsampling. My experience suggests the process is much too subtle to make a difference to most folks. Using this analogy, I was hoping for the grunge to be entirely scrapped away from the window, and what I saw was something every so slightly less grungy one would not notice.

[Sir Terrence the Terrible]

Thanks for the update, Sir T. But I'm a bit confused.

I'm wondering though if Dolby TrueHD is sometimes recorded at a native 96 kpbs?

According to Wikipedia, (here) (http://en.wikipedia.org/wiki/Blu-ray_Disc#Audio), Blu-ray supports Dolby TrueHD (lossless) at up to 24/96 for 8 channels or 24/192 for 5 channels. But is are these the non-upsampled rates? And if our players report 24/96 is there any way to know if this is native or upsampled?

Feanor, you are confusing the data rate with the sample rate. The sample rates you list are native sample rates, not upsampled rates. Those rates are established during production, and the process Dolby has come up with is done post production, and during encoding.

The upsampling process regardless of whether it is done on the disc, or within the player introduces something called pre-ringing or some other artifacting. The Apodizing filter eliminates the pre-ringing, but I am not sure there is enough pre-ringing occurring in the production of soundtracks to make a huge difference - hence why the effect I heard was so subtle it could be unnoticeable.

[Feanor]

Feanor, you are confusing the data rate with the sample rate. The sample rates you list are native sample rates, not upsampled rates. Those rates are established during production, and the process Dolby has come up with is done post production, and during encoding. ...
So ... by the time they get to the disc native and upsampled 96 look the same.


...
The upsampling process regardless of whether it is done on the disc, or within the player introduces something called pre-ringing or some other artifacting. The Apodizing filter eliminates the pre-ringing, but I am not sure there is enough pre-ringing occurring in the production of soundtracks to make a huge difference - hence why the effect I heard was so subtle it could be unnoticeable.
I'm heard of the pre-ringing issue which, in the simplest terms, is a response in the upsampled bitstream that precedes the actual transient the bitstream is supposed to be representing. I don't pretend to understand why this happens. People proposed that this signal-before-the-signal is audible and disagreeable.

I've also heard about "apodizing" filtering that reduces or eliminates pre-ringing, but I assure you I don't fully understand this either.

[Feanor]

All Bluray soundtracks are sampled at 48khz. ...
Really? Is this just the practice or is it theoretical limitation?

[Sir Terrence the Terrible]

So ... by the time they get to the disc native and upsampled 96 look the same.

Actually a 96khz native sample rate can potentially have high frequency information up to 48khz before it hits the brickwall filter. 48khz upsampled to 96khz will have no information above 24khz, but the filter has been moved from 24khz to 48khz. So upsampling is not adding information, it is just moving the brickwall filter up an octave. If done correctly, there will be added air, and a sense of smoothness to the audio.



I'm heard of the pre-ringing issue which, in the simplest terms, is a response in the upsampled bitstream that precedes the actual transient the bitstream is supposed to be representing. I don't pretend to understand why this happens. People proposed that this signal-before-the-signal is audible and disagreeable.

I've also heard about "apodizing" filtering that reduces or eliminates pre-ringing, but I assure you I don't fully understand this either.

With the high ambient levels of most homes, I seriously doubt you can hear the pre-ring filter directly. But you can hear its effects pretty clearly as a hardening and coarsening of the sound. To me it sounds like what you hear with Dolby Digital when it is bit challenged.

[Sir Terrence the Terrible]

Really? Is this just the practice or is it theoretical limitation?

Actually the Bluray format supports 8 channels of 24/192khz audio. However the post production community workflows are limited to 48khz because of the amount of resources any higher sample rate takes up. For instance, If I have 24 channels of 48khz audio, I can only have 12 channels of 96khz audio because it takes twice as much data and resources to work with it.

[E-Stat]

Just a background on TrueHD 96k, what Dolby does is upsample the 48khz sample rate of Bluray soundtracks to 96khz during encoding.
Does this allow for using the existing Dolby True HD codec found in processors today? Or, will this require a new one?

[Sir Terrence the Terrible]

Does this allow for using the existing Dolby True HD codec found in processors today? Or, will this require a new one?

This is a encoding process(and the brains of both formats codecs is in the encoder) so it will not require any changes or new decoder.

[E-Stat]

This is a encoding process(and the brains of both formats codecs is in the encoder) so it will not require any changes or new decoder.
Cool, thanks.

[bfalls]

Dolby's company theaters are the best in the business, second only to Disney's and Sony screening and home theater rooms. The system is top notch, and extremely well calibrated, so I was really looking forward to this.


What hardware is Sony running in their screening and HT rooms. We disassembled our three A/V authoring suites here in Indiana and moved a lot of the good hardware to California and New York. We sent many Genelec powered monitors and subs, Tannoy and Dunlavy SCIV speakers. A lot of Music Fidelity and Sonic Frontiers processors, expanders, D/A converters, ... I'm just curious what they run in the screening rooms for playback.

[Sir Terrence the Terrible]

What hardware is Sony running in their screening and HT rooms. We disassembled our three A/V authoring suites here in Indiana and moved a lot of the good hardware to California and New York. We sent many Genelec powered monitors and subs, Tannoy and Dunlavy SCIV speakers. A lot of Music Fidelity and Sonic Frontiers processors, expanders, D/A converters, ... I'm just curious what they run in the screening rooms for playback.

I think mostly all of the studios(with the exception of Disney) use Genelec's in their HT rooms, and JBL speakers in their screening rooms. We(Disney) use Revel in our HT rooms, and a custom design (by the same guy that built the system in my sig) for our screening rooms.

I would imagine all of that equipment you sent to California is probably heading to your gaming division in Redwood City. From what I understand, audio wise, that is where the action is.