Dolby TrueHD vs. DTS-HD Master Audio - Page 2

Originally Posted by Roger Dressler 

Which discs were filtered, and how do you know?

Originally Posted by pitviper33 

Surely the most famous example is the Master and Commander blu-ray. You can tell quite easily by listening to the first battle scene on the DVD for comparison. It's a HUGE difference. I own both discs. The DVD makes an excellent demo disc (for audio). It's one of the most engaging action scenes I've ever experienced in a movie. You FEEL each cannon blast. The same scene on the blu-ray is bland and uninvolving. It feels like just another battle sequence. Despite the dramatic improvement in picture quality, the neutered blu-ray has near zero replay value. I'll reach for the DVD every time.

Originally Posted by Kain 

Good discussion! I have a slight off-topic question though. Why do some movies on DVD/Blu-ray Disc have the bass filtered? Is it to "protect" home theaters?

Originally Posted by Roger Dressler 

Yes, that is well known. Kain made it seem as if this happens routinely.

Originally Posted by pitviper33 

Are you suggesting that it doesn't happen routinely? It certainly does. The M&C blu ray is just a particularly easy to demonstrate example of the effect it can have on the viewing experience. The real world contains lots of very low frequency bass. The microphones used to record real events pick up that bass. So anytime it doesn't make it to the disc, it must have been filtered out. Is that done to "protect" home theaters? I have no idea. I hope not, as it's very a misguided effort if so.

Originally Posted by Roger Dressler 

We are not discussing the filters that may have been used in the making of the original soundtrack. For a home release, unless one can compare it to the theatrical version, or as in the case of M&C, detect or measure the difference between two versions, there is no easy way to know if filtering was applied for a given home release or not.

Originally Posted by Roger Dressler 

We are not discussing the filters that may have been used in the making of the original soundtrack. For a home release, unless one can compare it to the theatrical version, or as in the case of M&C, detect or measure the difference between two versions, there is no easy way to know if filtering was applied for a given home release or not.

Originally Posted by pitviper33 

You obviously took a far more narrow view of the question than I did. It wasn't nearly specific enough to call his question invalid as you seem to be trying to do. The content on many discs is HPFed. The question is why.
If you don't know the answer, fine. Neither do I; I just have a guess or two. If you do know the answer, please enlighten us. If you have some piece of information that might help us narrow in on the answer, such as at what stage this filtering is taking place as you've alluded, why don't you share it? It'd be a lot more constructive than just telling the OP he's wrong for asking the question and me that I'm wrong for defending the question.

Originally Posted by pitviper33 

You obviously took a far more narrow view of the question than I did. It wasn't nearly specific enough to call his question invalid as you seem to be trying to do.

The content on many discs is HPFed. The question is why.

If you don't know the answer, fine. Neither do I; I just have a guess or two. If you do know the answer, please enlighten us. If you have some piece of information that might help us narrow in on the answer, such as at what stage this filtering is taking place as you've alluded, why don't you share it?

Originally Posted by pitviper33 

The content on many discs is HPFed.

Originally Posted by Roger Dressler 

Here is the entirety of the OP's original question: >>Why do some movies on DVD/Blu-ray Disc have the bass filtered? Is it to "protect" home theaters?<< Notice the specific mention of protecting home theaters? Notice he did not ask why soundtracks in movie theaters have the bass filtered? It seems pretty clear that he was asking why content heading home gets the bass filtered.

Originally Posted by Roger Dressler 

We all know about one famous example, M&C. Is he asking why it ever happened like in M&C? That one was investigated (I was one of the folks who did such investigation, and posted my findings).

Originally Posted by Roger Dressler 

If you are asserting many soundtracks are being filtered for home use, then please cite the evidence. If you are asserting that many movie soundtracks as released to theaters have HP filtering, that is a different matter altogether.

Originally Posted by Roger Dressler 

The answer is simple. Unintended subsonic content (i.e., noise, rumble) eats amplifier power and expends cone excursion to no useful purpose. It is good engineering practice to remove it. It can be remove at different points in the chain: the mic preamp, the predub sessions using a DAW (workstation), or in post production using a DFC (console).

Originally Posted by sdurani 

Besides 'Master & Commander', which seems to have been HPFed in error, which other discs are high pass filtered?

Originally Posted by pitviper33 

I see two questions there. The first is why content is filtered. The second is a proposed answer from him, formed as another question. I don't see that the second question has to limit the scope of the first. You read it one way; I read it another. Regardless, if we continue to argue the semantics of the question we'll just run around in circles and nobody learns anything. I vote we let the question that started all this be done at this point.
Okay, it makes perfect sense why unintended infrasonic content should be removed. But why was unintended infrasonic content there in the first place? Depending of course on the recording environment, shouldn't noise unrelated to the scene (infrasonic or otherwise) be pretty minimal? Applying a blanket HPF to everything seems a bit like throwing out the baby with the bath water doesn't it? The impact (no pun intended) of infrasonic cues to the realism of the playback experience is quite obvious. I can't believe that those creating the recordings or mixes at any stage are unaware of it.

Originally Posted by pitviper33 

I see two questions there. The first is why content is filtered. The second is a proposed answer from him, formed as another question.

I vote we let the question that started all this be done at this point.

Happen to remember where you posted that info? I've read a thread or two about it, but I don't know if I ever saw a nice conclusion.

Okay, it makes perfect sense why unintended infrasonic content should be removed. But why was unintended infrasonic content there in the first place?

Depending of course on the recording environment, shouldn't noise unrelated to the scene (infrasonic or otherwise) be pretty minimal?

Applying a blanket HPF to everything seems a bit like throwing out the baby with the bath water doesn't it?

The impact (no pun intended) of infrasonic cues to the realism of the playback experience is quite obvious. I can't believe that those creating the recordings or mixes at any stage are unaware of it.

Originally Posted by J_Palmer_Cass 

Read postings made by Filmmixer near the link below. The link is in the middle of the discussion about sub 20 Hz content.
QUOTE:
"And practically speaking, what if we could reproduce content down to 8-12Hz?
Should I filter it knowing it won't play anywhere else?
If I let it go, I know, based on experience, that I will over compensate the LFE down, and it will be anemic on 99% of the systems it plays back on...... and all that information takes up a lot if headroom (which is one of the reasons filtering isn't always a bad idea...)"
http://www.avsforum.com/t/1333462/the-new-master-list-of-bass-in-movies-with-frequency-charts/3510#post_21995228

Originally Posted by Roger Dressler 

Because mics have better hearing than people. They pick up stuff we do not notice.
People have gotten sick working in an office where the AC units shook the ceiling <10 Hz but no one knew why until spectral analysis was conducted. That same noise shows up in production sound.

Originally Posted by Roger Dressler 

Aside from M&C, who said a blanket HPF is applied?

Originally Posted by Roger Dressler 

Unintended subsonic content (i.e., noise, rumble) eats amplifier power and expends cone excursion to no useful purpose. It is good engineering practice to remove it. It can be removed at different points in the chain: the mic preamp, the predub sessions using a DAW (workstation), or in post production using a DFC (console).

Originally Posted by Roger Dressler 

It depends on what constitutes cues and realism. Can you give an example where infrasonics made an obvious difference in realism?

Originally Posted by pitviper33 

I won't claim to have any familiarity with the tools being used here, but shouldn't this kind of stuff be pretty easy to detect during mixing? And then couldn't the mixer tell whether it was intended or unintended content?

Actually I kind of thought you did: Maybe I misunderstood.

When haven't they?

This is surely up to interpretation, but I've found all of the well known scenes with substantial infrasonic content in the right places to be more engaging than similar scenes without. Hardly scientific, but I find it to be a very convincing effect. The example we've already discussed, M&C, is pretty easy to compare.

I shared my own feelings on the difference with and without for that example earlier in the thread. I've tried applying a 20Hz HPF on other famous scenes like War of the World (pod emergence) and How to Train Your Dragon (final dragon fight), and I found my own envelopment noticeably reduced.

Originally Posted by pitviper33 

Surely the most famous example is the Master and Commander blu-ray. You can tell quite easily by listening to the first battle scene on the DVD for comparison. It's a HUGE difference. I own both discs. The DVD makes an excellent demo disc (for audio). It's one of the most engaging action scenes I've ever experienced in a movie. You FEEL each cannon blast. The same scene on the blu-ray is bland and uninvolving. It feels like just another battle sequence. Despite the dramatic improvement in picture quality, the neutered blu-ray has near zero replay value. I'll reach for the DVD every time.

Originally Posted by Roger Dressler 

Ok. Let's say it is easily detected and decided it was unintended. So they'd filter it, no?

Originally Posted by Roger Dressler 

It's your assertion. The burden is on you to bring evidence.

Originally Posted by Roger Dressler 


That seems like a reasonable choice to me. A filter like that leaves plenty of gut-shaking and window rattling signals in place, but avoids problems with most home and theater systems.

It ain't real high fidelity but it avoids problems with 90% of the audio systems out there.

Also, LFE tracks are a zero-sum game. Any energy you add below 27 Hz subtracts from how much there can be above 27 Hz.

If that low. Theaters too.

Pinch yourself. It is very common for broad-line speaker manufacturers to include odd little gizmos like "subwoofers" with a single 6 1/2 driver.

Please tell me I'm imagining this:

http://www.polkaudio.com/products/pswi8m

;-)

Just barely if the speaker is clean. If the speaker is not clean that filter can be very audible due to the trouble that it keeps the driver out of.

I'll take the devil's advocate position here and argue that your evaluation, besides its exposure to your own personal bias, isn't about giving the contrary view all of the chances that nature can give it. If you filter out signal below a certain frequency you pick up headroom that you could invest in peaked-up response just above the filter corner frequency. There is no doubt that 30 Hz is far more audible and in its way enveloping than 15 Hz.

I say this as a person who is intimately familiar with and highly appreciative of subs wtth strong clean response down to 10 Hz. There is no doubt that with the right recording they are experiences. The phrase "listen to" fails! ;-)

But now we are talking about a product that we are selling to the mass market.

Originally Posted by Kain 

When they filter out the bass, does that mean that when the movie is played in a movie theater, you get the "whole" soundtrack including all the bass and when it hits home video, the bass is "cut out?"

Originally Posted by pitviper33 

Obviously. Where exactly are we going with this?

I'm being asked to show evidence that infrasonic content is noticeable? I just want to make sure I'm getting that right.

Originally Posted by arnyk 

Originally Posted by pitviper33 


Interesting idea there. I hadn't been thinking how if a significant portion of LFE energy is ULF, that soundtrack might come across as thin on systems that fail to reproduce it. That makes a lot of sense, and I don't see any easy was around it.

I'll read through some of the discussion in the movies with bass thread in the area you recommended. That thread is all over the place and tremendously long, so I haven't read most of it.

Originally Posted by arnyk 

I'll take the devil's advocate position here and argue that your evaluation, besides its exposure to your own personal bias, isn't about giving the contrary view all of the chances that nature can give it. If you filter out signal below a certain frequency you pick up headroom that you could invest in peaked-up response just above the filter corner frequency. There is no doubt that 30 Hz is far more audible and in its way enveloping than 15 Hz.
I say this as a person who is intimately familiar with and highly appreciative of subs wtth strong clean response down to 10 Hz. There is no doubt that with the right recording they are experiences. The phrase "listen to" fails! ;-)
But now we are talking about a product that we are selling to the mass market.