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[stewart_pk]

I've especially noticed it during the asteroid chase scene in Empires Strikes Back at repeatable moments.
I have JRiver decoding the DTS-HD 6.1 track and then down mixing it 2 channel.
KODI does not have the same issue.
Also if I play one of the other language tracks in JRiver which are 5.1 Dolby Digital there is no issue.

Any else having similar issue(s)?

[kalston]

Try disabling the LFE channel or applying a low pass filter (100 or 120hz) with the parametric equalizer. The Star Wars blu-ray audio engineers forgot to clean up the LFE channel so there is some garbage in there that may be noticeable on some setups. I've discussed the issue here : https://www.doom9.org/showthread.php?s=b6222a0ad2b59f6d1d2b24e5c25831c6&p=1714639#post1714639 and I own the Star Wars blu-ray as well and have noticed several occurrences of this problem (which I have fixed by using a low-pass filter as explained above).

Just to confirm, if you play the lossy DTS core you don't get the issue, right?

[Hendrik]

We've been thinking about this before, and we should probably low-pass the LFE before downmixing it.
Need to revise the options dialog a bit for this to make sense, will try to get to it in January.

[Hilton]

We've been thinking about this before, and we should probably low-pass the LFE before downmixing it.
Need to revise the options dialog a bit for this to make sense, will try to get to it in January.

Great, as long its optional?

[stewart_pk]

Just to confirm, if you play the lossy DTS core you don't get the issue, right?

I don't know how to do that but would really like to know how! Thanks for your response.

[stewart_pk]

OK, I did some experimenting and I don't think it has anything to do with LFE.
I put a low pass filter on L, R and Subwoofer at 250Hz at 12 d/B octave and there is no crackle at all.
So the crackle is at a considerably higher frequency.
I've done a bit of webbing and found that the Star Wars blurays with their 6.1 soundtrack may have an unusual channel ordering; but I'm not sure.

[jmone]

Your not the only one dusting off the old Star Wars discs at the moment.  I'd forgotten that these things have a 6.1 track with a channel layout that my AVR with 5.1 speaker setup does not like (I get no Dialogue) when MC was set to "source # of channels".  Changed it to use JRSS mixing and I got the Dialogue back but then got the crackling as well.

[Hendrik]

Great, as long its optional?

Why would you ever not lowpass the LFE when downmixing?  Do you want to have to turn it on when a file is badly mastered? That seems weird.

So the crackle is at a considerably higher frequency.

Thats exactly the problem - the LFE channel contains high frequency "noise" which is usually not audible because LFE speakers will not be able to play it. But if you mix it into L/R, it suddenly becomes audible since the L/R speakers of course can play these frequencies.
Low-passing the LFE before mixing gets rid of it. This is not something you can "emulate" in MC today though, since you can't put any filters in before the downmixing stage.

[kalston]

I don't know how to do that but would really like to know how! Thanks for your response.

I'm actually not sure how to do it now, it used to be simple - you could just remove the dtsdecoder.dll from the lav folder. It would be a little more tricky now, although you could just downgrade LAV version for the purpose of this test.

But yes, the crackle is precisely because the LFE channel contains higher frequencies than it should.

[blgentry]

Why would you ever not lowpass the LFE when downmixing?  Do you want to have to turn it on when a file is badly mastered? That seems weird.

Presumably the LFE channel is low pass filtered on almost every release.  As such, there is a phase shift applied by the 2nd, 3rd, or 4th order filter they use.  If you introduce another filter close enough to the original, you will introduce more phase shift and possibly attenuate the upper frequencies.  All of this depends on the frequency and slope of the original filter, and the new (MC) filter.

I'm not saying "it's a problem".  I'm saying "it's a consideration".

Brian.

[stewart_pk]

Thats exactly the problem - the LFE channel contains high frequency "noise" which is usually not audible because LFE speakers will not be able to play it. But if you mix it into L/R, it suddenly becomes audible since the L/R speakers of course can play these frequencies.
Low-passing the LFE before mixing gets rid of it. This is not something you can "emulate" in MC today though, since you can't put any filters in before the downmixing stage.

I see; thanks everyone for the responses.

Is there anyway to play the lossy DTS track within the DTS-HD track or could this feature be added in a future release?

[Hendrik]

Is there anyway to play the lossy DTS track within the DTS-HD track or could this feature be added in a future release?

There are no plans to do this, since it makes no sense to intentionally play a lower quality variant of the stream.

[stewart_pk]

There are no plans to do this, since it makes no sense to intentionally play a lower quality variant of the stream.

Except for when the so called higher quality stream has LFE mixing issues and the other doesn't

I would think it might be handy for troubleshooting.

[RD James]

Presumably the LFE channel is low pass filtered on almost every release.  As such, there is a phase shift applied by the 2nd, 3rd, or 4th order filter they use.  If you introduce another filter close enough to the original, you will introduce more phase shift and possibly attenuate the upper frequencies.  All of this depends on the frequency and slope of the original filter, and the new (MC) filter.

I'm not saying "it's a problem".  I'm saying "it's a consideration".

Brian.

Both DTS-HD and TrueHD store full range LFE channels with the assumption that the decoder will apply a low-pass filter.
120Hz 24dB/oct seems to be the lowest strength filter which eliminates any distortion in all the tracks that I've tested.

[stewart_pk]

We've been thinking about this before, and we should probably low-pass the LFE before downmixing it.
Need to revise the options dialog a bit for this to make sense, will try to get to it in January.

I hate to nag but I'd be a real happy boy if you could make this happen

[stewart_pk]

OK, it turns out I don't mind nagging

Bump!

[stewart_pk]

21.0.53 (2/29/2016)

2. NEW: Output Format DSP can lowpass the LFE/Subwoofer when downmixing, or exclude it from the downmix entirely.

Wow, thanks. I'm looking forward to trying this.

[Hendrik]

Note that this function is not quite perfect yet in the current build, and the remaining issues will be corrected on the next one.

[stewart_pk]

Note that this function is not quite perfect yet in the current build, and the remaining issues will be corrected on the next one.

No worries and I can confirm that some issues seem fixed and some don't. Looking forward to the next release, thanks.

[codpiece]

So, if you're using a stereo configuration, what is the recommended setting?

[RD James]

So, if you're using a stereo configuration, what is the recommended setting?

Once it's fixed, selecting a 120Hz low-pass filter should give the intended results.

[stewart_pk]

I'm getting some "poppy" or "ticking" like sounds in the right channel so I've reverted back to 21.0.50 from 21.0.54 and the problem is gone.

[Hendrik]

That will be fixed in an upcoming build, there was a silly mistake in the initial implementation.
You could keep using 54 and just disable the low-pass when downmixing by setting it to either discard LFR entirely or just not lowpass (which would be the .50 behavior).

[stewart_pk]

You could keep using 54 and just disable the low-pass when downmixing by setting it to either discard LFR entirely or just not lowpass (which would be the .50 behavior).

Thanks again, will do.

[stewart_pk]

That will be fixed in an upcoming build...

I have low pass set to 120Hz and I can report this is now fixed, wunderbar!