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Author Topic: Bass distortion in movies  (Read 8398 times)

amvolante

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Bass distortion in movies
« on: January 19, 2015, 09:53:41 pm »

Does anyone else have this issue?  It's only with movies.  Most notably, the Dark Knight and Batman Begins.  When the bass gets really deep it's like someone is crackling paper.  I never had this problem until version 20, but I haven't watched a movie in quite a while after upgrading+.  I used to have the equalizer turned on with the preamp volume lowered to prevent clipping, but when I turned it off there was no change.  I turned off all processing I had, no change.  I tried removing JRiver and all settings entirely and reinstalling with the version on the default download page, no change.  I tried removing dtsdecoderdll to see if it was corrupt, but no difference.  Music is fine.

Also, in vlc and kodi I don't have this problem.
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Fabith

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Re: Bass distortion in movies
« Reply #1 on: January 20, 2015, 03:00:55 am »

Maybe you have problems with Wasapi or the Volume settings.
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mwillems

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Re: Bass distortion in movies
« Reply #2 on: January 20, 2015, 08:24:12 am »

Does anyone else have this issue?  It's only with movies.  Most notably, the Dark Knight and Batman Begins.  When the bass gets really deep it's like someone is crackling paper.  I never had this problem until version 20, but I haven't watched a movie in quite a while after upgrading+.  I used to have the equalizer turned on with the preamp volume lowered to prevent clipping, but when I turned it off there was no change.  I turned off all processing I had, no change.  I tried removing JRiver and all settings entirely and reinstalling with the version on the default download page, no change.  I tried removing dtsdecoderdll to see if it was corrupt, but no difference.  Music is fine.

Also, in vlc and kodi I don't have this problem.

Two thoughts:

1) My personal experience has been that those two Batman movies have quite a bit of distortion on the LFE track.  I encountered this a year or so ago, and I tried to figure out what was wrong with my setup until I realized that the distortion was happening at the exact same spots in the films every time (there's car chase scene in which it is particularly bad, as I recall).  After that, I muted everything but the LFE and routed it to a pair of headphones and there was really terrible distortion on the bass in some scenes no matter what player I used.  So the distortion you're hearing may be "in the source," but that wouldn't explain why you're not hearing it in Kodi or VLC unless...

2) Your subwoofer may be damaged; that crinkling sound can be the sound of speaker damage (or plain old loose screws).  Normal audio content (i.e. CD content) only has bass down to 20Hz.  Sub/LFE channels on movies have bass down to 7 or 8Hz, which needless to say asks a lot more from a subwoofer in terms of mechanical motion.  Try downloading test tones (or use a software signal generator) and play a 10Hz tone and see if you hear the crinkling or not.

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6233638

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Re: Bass distortion in movies
« Reply #3 on: January 20, 2015, 08:36:48 am »

I seem to recall there being distortion in the audio tracks themselves on these movies too.
Of course, that's with MC decoding the audio so it could theoretically be a decoding error, but that seems extremely unlikely.
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Hendrik

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Re: Bass distortion in movies
« Reply #4 on: January 20, 2015, 08:43:44 am »

I've seen distortion in LFE tracks in many movies now. Often enough, the distortion is practically inaudible on actual subwoofer speakers, as the distortion is in much higher frequencies. If your sub is actually better at reproducing high frequencies, the LFE might benefit from a low-pass first.
If you downmix to stereo, it may also be beneficial to low-pass the LFE channel before mixing it into Left/Right.
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mojave

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Re: Bass distortion in movies
« Reply #7 on: January 20, 2015, 02:20:05 pm »

I've seen distortion in LFE tracks in many movies now. Often enough, the distortion is practically inaudible on actual subwoofer speakers, as the distortion is in much higher frequencies. If your sub is actually better at reproducing high frequencies, the LFE might benefit from a low-pass first.
If you downmix to stereo, it may also be beneficial to low-pass the LFE channel before mixing it into Left/Right.
DTS-HD and Dolby TrueHD are spec'd to have a fullrange single in the LFE channel with the decoder providing a low pass filter. I've been wondering for a while (several years actually) whether JRiver should have a low pass filter set as the default for decoding lossless audio in movies. Maxmercy at AVS Forum found the following when comparing the Arcsoft to a receiver's output:

The ArcSoft DTS decoder doesn't apply the 120Hz lowpass. When I add a 24dB/oct lowpass at 120Hz, my waveform looks nearly identical to yours.

I saw your discussion of bass distortion in the LAV Filters thread back in December, but I don't think LAV Filters needs to have a low pass added. If it is added in JRiver I would like it adjustable and defeatable. I believe receiver's give the option of using an 80 Hz - 200 Hz low pass on the LFE channel. Perhaps a 24 dB/octave lowpass filter could be added to the Audio > Settings section of Options called LFE Low Pass Filter for Multi-Channel Audio with a selection of 80,100,120, 200 or disabled. Users wanting more control and different slopes could just use PEQ.
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Hendrik

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Re: Bass distortion in movies
« Reply #8 on: January 20, 2015, 02:31:21 pm »

DTS-HD and Dolby TrueHD are spec'd to have a fullrange single in the LFE channel with the decoder providing a low pass filter. I've been wondering for a while (several years actually) whether JRiver should have a low pass filter set as the default for decoding lossless audio in movies. Maxmercy at AVS Forum found the following when comparing the Arcsoft to a receiver's output:

The ArcSoft DTS decoder doesn't apply the 120Hz lowpass. When I add a 24dB/oct lowpass at 120Hz, my waveform looks nearly identical to yours.

I saw your discussion of bass distortion in the LAV Filters thread back in December, but I don't think LAV Filters needs to have a low pass added. If it is added in JRiver I would like it adjustable and defeatable. I believe receiver's give the option of using an 80 Hz - 200 Hz low pass on the LFE channel. Perhaps a 24 dB/octave lowpass filter could be added to the Audio > Settings section of Options called LFE Low Pass Filter for Multi-Channel Audio with a selection of 80,100,120, 200 or disabled. Users wanting more control and different slopes could just use PEQ.

Expanding the current Subwoofer Low-Pass filter (which is used when JRSS produces the Subwoofer) would be quite easy. We just need a clean way to expand the options that way.
Any concrete suggestions? It should probably go into the Output Format DSP somewhere, into the Subwoofer group where the JRSS subwoofer is? But that might end up confusing, since its twice a similar option (cross-over and just lowpass)

PS:
If the specification suggests that the decoder should Low-Pass, it might be more generally useful if LAV could in fact do that.. afterall MC is not its only user.
On the other hand, I don't have such processing at all in LAV yet, so no framework to implement it with.
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mwillems

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Re: Bass distortion in movies
« Reply #9 on: January 20, 2015, 03:01:22 pm »

Expanding the current Subwoofer Low-Pass filter (which is used when JRSS produces the Subwoofer) would be quite easy. We just need a clean way to expand the options that way.
Any concrete suggestions? It should probably go into the Output Format DSP somewhere, into the Subwoofer group where the JRSS subwoofer is? But that might end up confusing, since its twice a similar option (cross-over and just lowpass)

Also, my understanding was that the JRSS subwoofer function doesn't currently interact with native LFE at all, so I typically keep it set to Silent (which has the side-effect of disabling all the options beneath it).  That UI behavior would need to change/be better explained if the new LFE-related option went there.

It might be the kind of thing better handled in bass management?
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Matt

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Re: Bass distortion in movies
« Reply #10 on: January 20, 2015, 03:20:16 pm »

I think an option in Audio like 'Enable low-pass on native subwoofer channel' would make sense.  That way it's configurable and it could default to true so normal people wouldn't have to worry about it.
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mojave

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Re: Bass distortion in movies
« Reply #11 on: January 20, 2015, 05:03:56 pm »

I think an option in Audio like 'Enable low-pass on native subwoofer channel' would make sense.  That way it's configurable and it could default to true so normal people wouldn't have to worry about it.
For someone that likes terms like WDM and IPC, I would think that sticking with correctly calling it the LFE channel would make sense.  ;D
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6233638

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Re: Bass distortion in movies
« Reply #12 on: January 20, 2015, 08:15:36 pm »

Here's a TrueHD sample from Blade Runner: http://www.datafilehost.com/d/19b79992
I think I have commented on this distortion in MC before.
 
From playing the track, it seems to need at least a 120Hz 24dB/Octave filter.
Anything less and there's obvious distortion in the downmix.

With the LFE track isolated in Audacity, 12dB/Octave seemed to be sufficient - though this is only one example, and others may be worse.
So it's possible that the requirements are going to be different depending on whether you are downmixing to stereo, or playing to an actual subwoofer.
I'm not sure whether you would want that to be user-selectable, or predefined.

If someone could post examples with timecodes, or sample files, that would be helpful.
I have the two Batman films, but haven't gone through them yet. I think TDK distorted in the long tunnel section, but I don't have the time to check that right now.
 
It's really difficult to properly test this however, since enabling a stereo downmix means that you cannot use a low-pass filter on the LFE channel when exporting an audio track. (as Output Format cannot be moved further down)
So most of my testing right now has been limited to what is actually audible in my setup, without being able to verify that it's completely removed from MC's output.

For someone that likes terms like WDM and IPC, I would think that sticking with correctly calling it the LFE channel would make sense.  ;D
Personally, I have a strong dislike for the use of "WDM" and "IPC" - they are not descriptive in anyway for regular users.
For this I would suggest something like "Enable low-pass on source LFE (subwoofer) channel" - that way both regular and technical users are covered.
If I was looking for an option, I'm with you, and would be looking for "LFE"
 

I wonder if this low-pass filter should be applied to all formats, or only the "HD" ones.
I wish I also had a way of comparing this to a "reference" device's output to get a better idea of how steep the low-pass filter should be.
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mojave

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Re: Bass distortion in movies
« Reply #13 on: January 21, 2015, 11:29:33 am »

I wonder if this low-pass filter should be applied to all formats, or only the "HD" ones.
I wish I also had a way of comparing this to a "reference" device's output to get a better idea of how steep the low-pass filter should be.
The low-pass filter should only be applied to TrueHD or DTS-HD. Since lossy codecs should already have a filter, then there will be more rolloff than intended. Since it only applies to the lossless codecs, I'm inclined think it belongs back in LAV Filters. It seems easier to implement in JRiver, though and wouldn't be as easy to turn off if implemented in LAV Filters.

As I mentioned above, maxmercy at AVS compared to a receiver and found that a 120 Hz 24dB/octave filter matched when using the Arcsoft decoder. I'm actually fine with this being the only option with a checkbox. Other high passes can be handled in Parametric Equalizer.



"Enable low-pass on source LFE (subwoofer) channel" - I like this wording. The only thing to add might be to clarify somehow that it is only for lossless audio.

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Hendrik

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Re: Bass distortion in movies
« Reply #14 on: January 21, 2015, 11:40:57 am »

Doing it codec-dependent in MC might be tricky, would indeed be better to do it in LAV then, however LAV operates in integer on those lossless codecs to not cause any modifications to the audio, so the LFE Low-Pass would ideally need to be in integer, or this channel needs to be converted to floating point and back.

We could of course still add an option to MC to disable the LAV option for easy configuration.
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6233638

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Re: Bass distortion in movies
« Reply #15 on: January 21, 2015, 12:40:26 pm »

Hmm, that's a difficult choice.
 
I'd much rather that the processing be handled by MC's 64-bit audio engine, than 24-bit int→float→int in LAV Filters.
As you say, the option in MC could control LAV Filters rather than actually processing it in MC, but I think I'd prefer the latter.
 
There's always the option to add a low-pass filter via the parametric EQ I suppose, though that would be applied to all formats rather than only the HD ones.
And what about SACD? That's a full-bandwidth LFE channel as well, and as far as I know is handled internally by MC's decoder rather than LAV.
 
I'm tempted to say just apply the low-pass filter to all LFE channels in MC, but I don't know what the consequences of that would really be with lossy formats. It seems like it shouldn't really matter, but I haven't tested it.
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mwillems

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Re: Bass distortion in movies
« Reply #16 on: January 21, 2015, 12:54:07 pm »

I'm tempted to say just apply the low-pass filter to all LFE channels in MC, but I don't know what the consequences of that would really be with lossy formats. It seems like it shouldn't really matter, but I haven't tested it.

If the lossy formats already have a low-pass dialed in, adding a second would steepen the roll-off and add additional phase shift for a few octaves below the low-pass.  On balance if it has to be all on or all off, I would say that 1) adding an unnecessary subwoofer low-pass for lossy material (especially as high as 120Hz) is probably to be preferred to 2) not lowpassing lossless material that should be filtered. 

In the former case you get a slightly steeper rolloff and some (maybe) audible phase shift; in the latter you get high frequency content at full volume fed to a speaker that can't handle it very well, producing breakup modes, etc.  The second one is much more likely to be audible than the first. 

Obviously the best case would be to handle content that needs the lowpass differently than other content, but that could be tough.
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6233638

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Re: Bass distortion in movies
« Reply #17 on: January 21, 2015, 01:43:13 pm »

Well I said I'd get around to it, though I was surprised to find that The Dark Knight is also TrueHD. I assumed it would be DTS-HD. http://www.datafilehost.com/d/71599540
 
120Hz 24dB/Octave doesn't seem necessary here, though lowpassing the LFE channel is, and I think that seems like a sensible choice.

in the latter you get high frequency content at full volume fed to a speaker that can't handle it very well, producing breakup modes, etc.  The second one is much more likely to be audible than the first.  
This is digital clipping/distortion I'm hearing, not due to driving the speakers too hard.

Obviously the best case would be to handle content that needs the lowpass differently than other content, but that could be tough.
Media Center can already identify the track being played, so I do wonder how difficult it would actually be.
 
Just automatically lowpass any LFE channel which is not contained in a lossy format. (TrueHD, DTS-HD, LPCM, FLAC, SACD etc.)
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dean70

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Re: Bass distortion in movies
« Reply #18 on: January 21, 2015, 02:36:39 pm »

I have 120Hz 24dB/Octave rolloff baked into the LFE Convolution filters. Any option added for this will be defeatable?
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amvolante

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Re: Bass distortion in movies
« Reply #19 on: January 23, 2015, 01:01:20 am »

Two thoughts:

1) My personal experience has been that those two Batman movies have quite a bit of distortion on the LFE track.  I encountered this a year or so ago, and I tried to figure out what was wrong with my setup until I realized that the distortion was happening at the exact same spots in the films every time (there's car chase scene in which it is particularly bad, as I recall).  After that, I muted everything but the LFE and routed it to a pair of headphones and there was really terrible distortion on the bass in some scenes no matter what player I used.  So the distortion you're hearing may be "in the source," but that wouldn't explain why you're not hearing it in Kodi or VLC unless...

2) Your subwoofer may be damaged; that crinkling sound can be the sound of speaker damage (or plain old loose screws).  Normal audio content (i.e. CD content) only has bass down to 20Hz.  Sub/LFE channels on movies have bass down to 7 or 8Hz, which needless to say asks a lot more from a subwoofer in terms of mechanical motion.  Try downloading test tones (or use a software signal generator) and play a 10Hz tone and see if you hear the crinkling or not.



Thanks for the tips.  I'm sorry for the late reply (I thought I would get emails of new posts).  The distortion is at the same spots, notably in the Dark Knight during the lower street chase.  It may be relevant to others, but I'm not using a sub.  I'm using headphones.  I hope this doesn't matter, because like I said I didn't have this problem before.  I'll try some more movies and post back if/when I find more examples.
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dean70

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Re: Bass distortion in movies
« Reply #20 on: January 23, 2015, 01:09:00 am »

Do you have Loudness enabled? I have seen it push the bass into clipping with content that is already too high in the bass region.
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amvolante

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Re: Bass distortion in movies
« Reply #21 on: January 23, 2015, 01:14:54 am »

Do you have Loudness enabled? I have seen it push the bass into clipping with content that is already too high in the bass region.

No, it's always been turned off.  When I open DSP Studio and look at the peak level it can be at 16% and still have distortion, unless I'm misunderstanding something.
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kstuart

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Re: Bass distortion in movies
« Reply #22 on: January 23, 2015, 09:39:22 pm »

Which headphones and which amp ?

amvolante

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Re: Bass distortion in movies
« Reply #23 on: January 23, 2015, 09:46:05 pm »

Tried onboard sound, a Burson hd-160, Stello HP 100, and an audioquest dragonfly.  For headphones I tried my sennheiser hd650s and Ultrasone Signature DJ.  I don't think it's component related since it's fine with kodi and vlc.
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ronkupper

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Re: Bass distortion in movies
« Reply #24 on: July 26, 2015, 07:05:52 pm »

[Not sure if I should open a new thread, it is related to the op topic]

In short -
I found that using a Subwoofer limiter in PEQ was the only thing that helped (mine is set to -20db) and wanted to share / get your opinion.

Details -
Not sure if I could call it distortion but I was experiencing really unproportional levels of bass only in multi-channel video content and only in specific parts in the video.
Examples of these parts are - HBO logo opening on GoT, Godzilla opening scene when the bomb explodes and recently Get Hard - flame throwing scene at 01:11:45.

Last occasion it got so loud that the sub (JL Audio e112) maxed out and got me concerned enough to search about it, when I found this thread.

For indication - in these parts the DSP Analyzer have the Sub line almost completely flatted up and, if turned on, the sub excursion is ridiculous (Again - only on specific "offending" parts in some videos, rest is fine even on the same video).

I've tried turning off Loudness and enabling a low-pass 120hz filter on the sub but these only helped marginally. (A 60hz low-pass did help but meant losing content on the LFE).

Finally, setting a PEQ Subwoofer limiter (Using several tries on an offending part to determine the needed level) was the only thing that helped and it seems to have done so without affecting anything else - only the offending parts were seem to be tamed.

My biggest concern was that any adjustment would also affect music content (my primary usage for the system) but the limiter seems to only apply to the LFE channel and does not have any effect on stereo content with bass management.

Thoughts?
Any insight of what could be the culprit for this phenomenon?
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