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Author Topic: Help using PEQ to downmix movies to 2-channel  (Read 4803 times)

PGibby

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Help using PEQ to downmix movies to 2-channel
« on: April 07, 2017, 08:38:00 am »

Hello all,

I've been attempting to downmix 7 channel movie tracks to play on my 2 channel system using the PEQ. I've yet to get the center channel track to play through my speakers. Up to this point, I've used JRSS downmixing and its worked perfectly, but I'd like to experiment with using PEQ to downmix to adjust channel levels (like boost the center relative to the others).

Here's my settings in DSP studio:

Output format:
No Output encoding
set to 2 channels (stereo)
No upmixing/downmixing

Parametric Equalizer:
I've ADDED sub, SL, SR, RL, RR, and center to L and R

Convolution:
This is on. I created the FIR filters in DRC Designer


I'm sure I'm missing something simple. My end goal is to be able to independently adjust one channel, mainly the center, for movies. I'd like to boost the center just a little over what JRSS downmixing does.

Thanks!
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mojave

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #1 on: April 07, 2017, 09:12:45 am »

Since you set Output Format to 2 channels (stereo), then only Left and Right will be affected by the Parametric Equalizer.

To do what you want you need to set output to 7.1 channels. However, your DAC might not accept 8 channels so you are stuck with having JRiver downmix automatically by using JRSS.

Couple of other notes:
  • When you add all the other channelw, you should first do a volume adjustment of about - 7 dB to  -10 dB in order not to clip the stereo channels.
  • All channels need to be lowered by 10 dB in order to match the subwoofer's level for combining channels.
  • I recommend only downmixing the L,R,C, and LFE to the stereo channels. The surround channels just muddy the two channel mix. If you listen to the 2 channel track on just about any movie or concert, the surround channels have not been mixed in. Who would want rear sounds from the front speakers?
  • Use Tools > Advanced Tools > Volume Calibration to ensure your down mix has the correct levels for sub vs other speakers
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PGibby

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #2 on: April 07, 2017, 09:21:48 am »

Since you set Output Format to 2 channels (stereo), then only Left and Right will be affected by the Parametric Equalizer.

To do what you want you need to set output to 7.1 channels. However, your DAC might not accept 8 channels so you are stuck with having JRiver downmix automatically by using JRSS.

Couple of other notes:
  • When you add all the other channelw, you should first do a volume adjustment of about - 7 dB to  -10 dB in order not to clip the stereo channels.
  • All channels need to be lowered by 10 dB in order to match the subwoofer's level for combining channels.
  • I recommend only downmixing the L,R,C, and LFE to the stereo channels. The surround channels just muddy the two channel mix. If you listen to the 2 channel track on just about any movie or concert, the surround channels have not been mixed in. Who would want rear sounds from the front speakers?
  • Use Tools > Advanced Tools > Volume Calibration to ensure your down mix has the correct levels for sub vs other speakers

Oh the DAC won't do that, its a vintage Sonic Frontiers stereo dac. haha
So, it sounds like i'm stuck is JRSS? Any way to boost just the center channel track with JRSS?

Thanks for you help!

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muzicman0

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #3 on: April 07, 2017, 09:31:11 am »

Any way to boost just the center channel track with JRSS?

Thanks for you help!
If so, that would be fantastic!!! 
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PGibby

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #4 on: April 07, 2017, 12:04:59 pm »

If so, that would be fantastic!!!

Yes. I'm not knowing enough to know how difficult this would be.

My stuff is mainly used for music, but we'll put on a movie a couple times a month. Would put icing on the cake to have the independent channel volume adjustment.
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narbi

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #5 on: April 07, 2017, 02:15:27 pm »

I would recommend to go the dolby/dts path for the downmix, it is by far the best result you can get.

Output set to 7.1
Discard LFE if you're not using a subwoofer, most low effects are present in the LCR anyway, and you speakers may not like it. That way you won't have to lower volume on all channels.
Add RL to SL, and RR to SR
Add center to left and right @-3db on both
Add SL to left @-3db, SR to right @-3db

This will work for whatever signal you use, be it stereo, 5.1 or 7.1
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PGibby

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #6 on: April 07, 2017, 02:21:17 pm »

I would recommend to go the dolby/dts path for the downmix, it is by far the best result you can get.

Output set to 7.1
Discard LFE if you're not using a subwoofer, most low effects are present in the LCR anyway, and you speakers may not like it. That way you won't have to lower volume on all channels.
Add RL to SL, and RR to SR
Add center to left and right @-3db on both
Add SL to left @-3db, SR to right @-3db

This will work for whatever signal you use, be it stereo, 5.1 or 7.1

I am using a sub (a home brew Rythmik 15"), but its ran off the out of my amp, so that actually doesn't matter. I've downmixed all frequencies using JRSS on that since day one. The speakers and sub aren't complaining there.

I'll give your setup a try when I get home.

Thanks
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narbi

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #7 on: April 07, 2017, 02:33:06 pm »

If you use a subwoofer you can downmix LFE.
But its level will not be +10 over the other speakers, as this is when 5 channels are actually output in real life (you use 2). It is encoded at the same level as any other front channel alone.
Your LFE level should be between +4 to +6, max.
Technically, in your setup, adding the subwoofer channel to left and right with no gain at all should be around the right levels.

For the record, the +10 of the LFE channel is only there to get in the end the same power response from one speaker (the subwoofer) as all the other speakers acoustically summed.
A correlated sum of 2 speakers is +6db (typically under 80Hz, when speakers are close to each other : twice the surface, and twice the power), otherwise it will be in-between stereo and mono sum due to the imperfect sum between the speakers in the room, so between +3 and +6 for 2 channels (typically 4-5).

It would probably be better to output the subwoofer channel separately to have more precise control on the levels.
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PGibby

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #8 on: April 07, 2017, 02:37:14 pm »

If you use a subwoofer you can downmix LFE.
But its level will not be +10 over the other speakers, as this is when 5 channels are actually output in real life (you use 2). It is encoded at the same level as any other front channel alone.
Your LFE level should be between +4 to +6, max.
Technically, in your setup, adding the subwoofer channel to left and right with no gain at all should be around the right levels.

For the record, the +10 of the LFE channel is only there to get in the end the same power response from one speaker (the subwoofer) as all the other speakers acoustically summed.
A correlated sum of 2 speakers is +6db (typically under 80Hz, when speakers are close to each other : twice the surface, and twice the power), otherwise it will be in-between stereo and mono sum due to the imperfect sum between the speakers in the room, so between +3 and +6 for 2 channels (typically 4-5).

It would probably be better to output the subwoofer channel separately to have more precise control on the levels.

Awesome...thanks a bunch.

I know I'm trying to tweak something ideally setup for 2-ch music to movies, so it wont be 'perfect'. But I'd like to experiment a little and see what I can do with it.

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phusis

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #9 on: April 08, 2017, 07:10:36 pm »

Since you set Output Format to 2 channels (stereo), then only Left and Right will be affected by the Parametric Equalizer.

To do what you want you need to set output to 7.1 channels. However, your DAC might not accept 8 channels so you are stuck with having JRiver downmix automatically by using JRSS.

Couple of other notes:
  • When you add all the other channelw, you should first do a volume adjustment of about - 7 dB to  -10 dB in order not to clip the stereo channels.
  • All channels need to be lowered by 10 dB in order to match the subwoofer's level for combining channels.
  • I recommend only downmixing the L,R,C, and LFE to the stereo channels. The surround channels just muddy the two channel mix. If you listen to the 2 channel track on just about any movie or concert, the surround channels have not been mixed in. Who would want rear sounds from the front speakers?
  • Use Tools > Advanced Tools > Volume Calibration to ensure your down mix has the correct levels for sub vs other speakers

Only just now found out that the feature in the DSP Studio (under Output Format) "Detect stereo sources in surround (pseudo-surround)" had been ticked default, and that switching off this feature seemed to enhance the clarity and stability of the 2-channel sound (incl. sub) when watching Blu-rays.

Does the none-use of this feature have a similar effect to not downmixing the surround channels, or are they still downmixed to 2-channel when using JRSS downmixing? Why is this feature on as default?
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mojave

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #10 on: April 11, 2017, 09:43:43 am »

Only just now found out that the feature in the DSP Studio (under Output Format) "Detect stereo sources in surround (pseudo-surround)" had been ticked default, and that switching off this feature seemed to enhance the clarity and stability of the 2-channel sound (incl. sub) when watching Blu-rays.

Does the none-use of this feature have a similar effect to not downmixing the surround channels, or are they still downmixed to 2-channel when using JRSS downmixing? Why is this feature on as default?
TV shows might send a 5.1 channel track but only have content in the left and right. When the "Detect stereo sources" option is checked, then JRiver will detect this and can upmix the 2 channels to 5.1 if one has JRSS turned on. Because a TV show may start out with nothing in the surround channels, JRiver could falsly assume there will be no surround content at all. The check mark is there to let one manually turn off the detection in the case of a false positive. It is on by default because it was the default behavior before the check box was added in 19.0.134. It was initially added just for some testing, but I guess Hendrik never removed it again.

19.0.132 (4/30/2014)
2. Changed: Increased the threshold of the pseudo-surround detection to reduce the risk of false positives.
3. NEW: Added an option to disable pseudo-surround detection in Output Format DSP.
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phusis

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Re: Help using PEQ to downmix movies to 2-channel
« Reply #11 on: April 19, 2017, 08:42:23 am »

TV shows might send a 5.1 channel track but only have content in the left and right. When the "Detect stereo sources" option is checked, then JRiver will detect this and can upmix the 2 channels to 5.1 if one has JRSS turned on. Because a TV show may start out with nothing in the surround channels, JRiver could falsly assume there will be no surround content at all. The check mark is there to let one manually turn off the detection in the case of a false positive. It is on by default because it was the default behavior before the check box was added in 19.0.134. It was initially added just for some testing, but I guess Hendrik never removed it again.

19.0.132 (4/30/2014)
2. Changed: Increased the threshold of the pseudo-surround detection to reduce the risk of false positives.
3. NEW: Added an option to disable pseudo-surround detection in Output Format DSP.


Thanks for the update on this.
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