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Discussion Starter #1
FAQ: Denon 2500, Panasonic DMP-BD10, Panasonic DMP-BD30 "LFE Bug"

Update:Issue is resolved on DMP-BD30 ONLY with firmware v1.6.

There is currently no resolution for Denon 2500 or DMP-BD10.
What is the issue?

The LFE channel (the .1 in 5.1 or 7.1) for PCM output over HDMI is 5db lower than it should. This applies to any tracks internally decoded to PCM or native PCM track on the disc.

What is a LFE?

The LFE or Low Frequency Effect is channel that contains frequencies below 120Hz. It is the ".1" in 5.1 or 7.1 tracks. It contains sounds designed to go exclusively to the sub woofer.

Is analog affected?

No. Analog does not appear to be affected. The output leaving the mixer is -5db but the LFE channel is amplified 5db after DAC (digital to analog conversion) so it is at the proper level.

Is SPDIF (digital out, optical out) affected?

No. This only affect PCM output on the LFE channel. PCM is limited to 2 channels (Left & right) over SPDIF. There is no LFE output to be affected.

Is bitstream output affected?

No. Bitstream output which is sending the raw compressed track is not affected. DD, DTS, DD+, TrueHD, DTS-HD, DTS-HD MA tracks are NOT affected if the player output is bitstream. Regardless of the player settings LPCM tracks are always sent as PCM so LPCM tracks on a BD disc output over HDMI will always be affected.

So if I have player set to bitstream to a compatible receiver (Onkyo-705) I am not affected?

No. LPCM tracks on the disc are output as PCM regardless of player settings. Since they are output as PCM they will be affected. There is currently no player setting to bypass the issue when playing a PCM track.

Can't I just boost the LFE channel +5db on my AVR (receiver)?

Virtually all AVR only allow lowering the LFE channel not raising it. If you AVR has a +5db setting it could compensate but I am not aware of any AVR that has such a setting. This is not the same thing as boosting the sub (see next questions).

Can't I just boost the subwoofer output +5db on my AVR (receiver)?

Not if you are using any bass management. Most HT setups redirect bass below a certain cutoff (40Hz, 60Hz, 80Hz) from main speakers to the subwoofer. Boosting the sub +5db will make the LFE channel have proper level but now the redirected bass from other 5 or 7 channels is now running "+5db too hot".

I am not using any bass management (speakers set to "large"). Can I boost subwoofer output +5db?

Yes. If the AVR is not applying ANY bass management then all bass from main channels goes to main speakers. There is no redirected bass, only the LFE channel goes to the subwoofer. The sub should be raised +5db for LPCM tracks and set to normal on all other tracks. For bass management to be turned off all speakers must be able to handle full range as main channels routinely have bass
 

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Excellent summation!
 

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Discussion Starter #5

Quote:
Originally Posted by mtntrance /forum/post/12925805

How do you know the Denon has it? Thanks.

It was confirmed by Roger (from Dolby) in the BD30 thread. I will try to locate and quote the actual post tomorrow.
 

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Just curious, how was it or [by who] confirmed that the analogs are not affected?


Also how do we know that the uncompressed signal enters the "mixer" when the secondary audio is set to off [as it should be] to avoid such manipulation in the first place? [Same goes for the +5db boost after DA conversion] I'm not saying it doesn't or can't but I wonder where your info on this comes from, or is it just a theory at this point?


thanks.
 

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Is the LFE encoded 5db lower on all the discs, so it is the player's proper job to raise it?
 

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Quote:
Originally Posted by Kilian.ca /forum/post/12932495


Is the LFE encoded 5db lower on all the discs, so it is the player's proper job to raise it?

The issue has nothing to do with the encoding. It's about the decoding within the player.
 

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Quote:
Originally Posted by thehun /forum/post/12930848


Just curious, how was it or [by who] confirmed that the analogs are not affected?


Also how do we know that the uncompressed signal enters the "mixer" when the secondary audio is set to off [as it should be] to avoid such manipulation in the first place? [Same goes for the +5db boost after DA conversion] I'm not saying it doesn't or can't but I wonder where your info on this comes from, or is it just a theory at this point?


thanks.

Both were confirmed by Roger Dressler from Dolby.

5db gain

Confirmation of LFE issue difficult to resolve


Others have tested as well. I wish we were making this up but no one is.
 

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Quote:
Originally Posted by Donnie Eldridge /forum/post/12932764


The issue has nothing to do with the encoding. It's about the decoding within the player.

So, as previously pointed out, LFE leaving the mixer is -5db, and that is the incorrect step?
 

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Quote:
Originally Posted by namechamps /forum/post/12923243

FAQ: Denon 2500, Panasonic DMP-BD10, Panasonic DMP-BD30 "LFE Bug"

What is the issue?

The LFE channel (the .1 in 5.1 or 7.1) for PCM output over HDMI is 5db lower than it should. This applies to any tracks internally decoded to PCM or native PCM track on the disc.

What is a LFE?

The LFE or Low Frequency Effect is channel that contains frequencies below 120Hz. It is the ".1" in 5.1 or 7.1 tracks. It contains sounds designed to go exclusively to the sub woofer.

Is analog affected?

No. Analog does not appear to be affected. The output leaving the mixer is -5db but the LFE channel is amplified 5db after DAC (digital to analog conversion) so it is at the proper level.

Is SPDIF (digital out, optical out) affected?

No. This only affect PCM output on the LFE channel. PCM is limited to 2 channels (Left & right) over SPDIF. There is no LFE output to be affected.

Is bitstream output affected?

No. Bitstream output which is sending the raw compressed track is not affected. DD, DTS, DD+, TrueHD, DTS-HD, DTS-HD MA tracks are NOT affected if the player output is bitstream. Regardless of the player settings LPCM tracks are always sent as PCM so LPCM tracks on a BD disc output over HDMI will always be affected.

So if I have player set to bitstream to a compatible receiver (Onkyo-705) I am not affected?

No. LPCM tracks on the disc are output as PCM regardless of player settings. Since they are output as PCM they will be affected. There is currently no player setting to bypass the issue when playing a PCM track.

Can't I just boost the LFE channel +5db on my AVR (receiver)?

Virtually all AVR only allow lowering the LFE channel not raising it. If you AVR has a +5db setting it could compensate but I am not aware of any AVR that has such a setting. This is not the same thing as boosting the sub (see next questions).

Can't I just boost the subwoofer output +5db on my AVR (receiver)?

Not if you are using any bass management. Most HT setups redirect bass below a certain cutoff (40Hz, 60Hz, 80Hz) from main speakers to the subwoofer. Boosting the sub +5db will make the LFE channel have proper level but now the redirected bass from other 5 or 7 channels is now running "+5db too hot".

I don't notice this issue with my player. Are you sure it is affected?

If your player is one of the affected players then you have the bug. It isn't a player build issue but rather a design issue that affects all players of that model. Stating 100% that a player is not affected without doing a comparison to another player is not possible. If during a point in the movie the LFE channel hits 85db, then 80db will be output. A viewer has no way to know the track is 85db. Without a frame of reference how can it be determined that 80db is right or too low? It may be possible to say "it doesn't bother me", "even with the bug output is good" but saying the bug doesn't exist is simply wrong.

So running the speakers large if they are capable of low bass and boosting the subwoofer level would compensate?

On the same line would setting the crossover to 40Hz would minimize the issue?
 

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The thing that would alarm me the most is that the issue exists even when the player is set to bitstream. This says that there is no way to get a native PCM track out without the player putting its dirty paws on it to apply processing I'm specifically trying to avoid by using bitstreaming in the first place.


Does this imply that the player is applying bass management to native PCM tracks even when set to bitstream?


Do other players apply processing to a native PCM track when the player is set to bitstream? Maybe this is actually also part of the design bug in this player.
 

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So, if my understanding is correct...this only effects Uncompressed PCM soundtracks rather than those decoded to LPCM in the player (e.g. TRUE HD)?


I can't imagine this would be the case outputing LPCM from a TRUE HD soundtrack as then the player would be augmenting the signal...
 

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Discussion Starter #14

Quote:
Originally Posted by thebland /forum/post/12937818


So, if my understanding is correct...this only effects Uncompressed PCM soundtracks rather than those decoded to LPCM in the player (e.g. TRUE HD)?


I can't imagine this would be the case outputing LPCM from a TRUE HD soundtrack as then the player would be augmenting the signal...

Not exactly. It doesn't matter what the SOURCE is. What matter is the OUTPUT. If the output is PCM then the signal is altered.


LPCM -> PCM = altered

DD -> decoded to PCM = altered

TrueHD -> decoded to PCM = altered

TrueHD -> bitstream = NOT ALTERED

DD -> bitstream = NOT ALTERED
 

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Discussion Starter #15

Quote:
Originally Posted by Mcguinn /forum/post/12937137


So running the speakers large if they are capable of low bass and boosting the subwoofer level would compensate?

I don't like the term "large" because it can vary from AVR to AVR. If your AVR applies 0 bass management (i.e all sound from 20Hz to 20KHz on main channels is sent to main speakers). Then yes +5db on the subwoofer will compensate exactly because only the LFE is -5db and the sub is ONLY playing the LFE channel.

Quote:
On the same line would setting the crossover to 40Hz would minimize the issue?

All depends on the track (how much
 

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Quote:
Originally Posted by thebland /forum/post/12937818


So, if my understanding is correct...this only effects Uncompressed PCM soundtracks rather than those decoded to LPCM in the player (e.g. TRUE HD)?


I can't imagine this would be the case outputing LPCM from a TRUE HD soundtrack as then the player would be augmenting the signal...

Any PCM out of the player will be affected, including TrueHD>PCM, etc....
 

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Quote:
Originally Posted by sergiohm /forum/post/12932811


Both were confirmed by Roger Dressler from Dolby.

5db gain

Confirmation of LFE issue difficult to resolve


Others have tested as well. I wish we were making this up but no one is.

Your last comment was unnecesarry there are plenty of misinformation on these boards, I was simply looking for info here that has credibility which those from Roger qualifies as such, so thanks for the links.
 

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What I don't get is, and Roger may explain this, it's obvious that Panasonic "corrupts" the signal but not by design but rather just a "mistake" somewhere, as I can't imagine this was done intentionally, so all they need is to "undo" the mistake. But so far there is no word what the source of the problem, only the symptoms. Now that Denon is reportedly has the same issue, it seems they just dressed up and re badged the BD30 and sell it for double. Not the first time they have done this, maybe to avoid the embarrassment, they lend a helping hand to Panasonic to solve this quickly? One can hope.
 

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Some background: The PCM LFE signal is supposed to be 10dB down compared to the other PCM signals. It is recorded that way so that explosions and stuff can be carried in the LFE channel without clipping during transmission to the AVR and initial processing in the AVR. This is also true about analog LFE sent to an AVR over multi-channel analog connections. A properly designed AVR boosts the LFE back up the necessary 10dB before adding in any bass steered to the subwoofer from the main speakers and sending the combo out to the subwoofer.


If bass steering happens inside the player (prior to multi-channel analog output from a player equipped that way), then you have cases where the LFE is sent over to the AVR as 15dB down to account for the extra bass that may have been contributed from main speaker channels during that bass steering in the player. What it looks like is happening is that these particular players are dropping the LFE coming in off the disc that extra 5dB INCORRECTLY.


For more background on this whole LFE issue, see this thread from the Audio Theory forum here.

http://www.avsforum.com/avs-vb/showthread.php?t=748147


Note that the 10dB lower LFE, and the boosting of it back to normal in the AVR, is nothing new. It has been this way essentially forever in traditional DD5.1 and DTS for example.


When you send such a bitstream to the AVR, the LFE encoded within the bitstream is already 10dB down, but the AVR boosts it during the decode. Since these players are not decoding such bitstreams before sending them to the AVR, there is no place for them to make the mistake of dropping the LFE the erroneous, extra 5dB.


When you send PCM to the AVR the LFE is supposed to be 10dB down, and the AVR is supposed to boost it back up again prior to mixing with steered bass and sending the result to the subwoofer. But the AVR is not expecting an ADDITIONAL 5dB drop in the LFE coming from the player. Apparently these players are doing this both to raw PCM tracks and to PCM resulting from decoding bitstreams inside the player.


Depending upon the signal path architecture it may be easier or harder for them to eliminate this bogus 5dB drop.

--Bob
 

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Quote:
Depending upon the signal path architecture it may be easier or harder for them to eliminate this bogus 5dB drop.

Well that's just it,the signal supposed to be untouched, if the secondary decoder is set to off. I don't even know why it even enters into the mixer as it's been stated, it really should just bypass everything....
 
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