Old 08-16-2021, 04:10 PM   #1
harris238
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Default Reaper Render Stats not matching Master Mix (FIXED)

See attached screen shot. You can see that the master mix is not showing any clipping (everything is staying at -0.2 or below), but the stats area is showing clipping and red lines on the stereo waveform. I have a limiter on the stereo bus, set to a max peak of -0.1. Any idea what's going on here?
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Old 08-16-2021, 04:26 PM   #2
schwa
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What’s the project sample rate?
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Old 08-16-2021, 05:04 PM   #3
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The VU meters are the levels at the master bus, but the render peaks drawing and the clip statistics are calculated from the actual rendered file. What you are seeing is most likely the difference between the levels at the project sample rate and the levels after the render resampling.

You could fix this various ways:

1. Change the project sample rate to match the rendered sample rate, which will cause the recorded media to get resampled pre-fx.

2. Normalize the rendered file (click the normalize button in the render dialog).

3. Lower the master fader
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Old 08-16-2021, 05:12 PM   #4
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Project sample rate is 96kHz, and I'm converting to 44.1kHz in the render. What if I render at the same sample rate, then import to a new project and then down sample? Will that fix the issue?

I've heard of sample rate conversion causing some "mid-sample peaks" but it's nuts to me that even with a limiter on the master bus it's still allowing clipping. Is this normal behavior for a DAW? I used to use Logic and never ran in to this problem.
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Old 08-16-2021, 05:43 PM   #5
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Also, what if I don't want the sample rate conversion to happen pre-effects? I use Universal Audio plugins, and per documentation, the plugins render and perform better at higher sample rates, so I want my effects to be processed at 96kHz. This seems like quite a limitation...
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Old 08-16-2021, 05:55 PM   #6
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Assuming the issue is in fact sample rate conversion, which is very likely, 1.5dB is definitely possible. In fact, the limiter is contributing to the magnitude of the difference, because it's squaring off peaks that the sample rate conversion then re-interpolates.

Regarding other DAWs, it's possible that you just didn't *see* the issue there, just as you wouldn't see it in REAPER if not for the rendered peaks display and render statistics.

If you want to be absolutely sure the rendered file is under +0dB, the easiest thing to do is simply normalize to -0.2dB or whatever in the render dialog.
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Old 08-16-2021, 06:06 PM   #7
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I really do not want to normalize anything...This completely changes the dynamics of the music and the mix. Bob Katz on normalization:

https://www.digido.com/ufaqs/normalization/

And, even so, why do the render stats show clipping but the actual master mix meter on the render dialogue *does not* show clipping or peaking? Even from a Reaper-design standpoint, shouldn't these two things show the same information? I'm confused why they're at all different.
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Old 08-16-2021, 06:54 PM   #8
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The render meters are literally the master track meters (or the individual track meters if you are rendering stems), pre-sample rate conversion. As a result of this conversation we'll probably change the render meters to reflect the actual rendered file levels, post-sample rate conversion.

The bottom line is, your limiter is squaring off the peaks at the master bus, and sample rate conversion, by design and as expected, is restoring at least part of the missing peaks via interpolation.

As I wrote above, you have three choices if you want the rendered file under +0dB.

1. You can feed the master limiter at the rendered sample rate. I know you wrote the plugins "perform better at higher sample rates" but in this scenario, feeding the limiter at the lower sample rate is definitely a better result than feeding the limiter at a higher sample rate and then downsampling.

2. You can normalize. Normalizing does not change dynamics. No disrespect to Bob Katz but normalizing also does not introduce "distortion." The article you linked to is basically saying don't normalize because it's unnecessary, but in this case, it's necessary (unless you do #1 instead).

3. Lower the master fader, which is functionally equivalent to normalizing after rendering.
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Old 08-16-2021, 06:57 PM   #9
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Quote:
Originally Posted by schwa View Post
The render meters are literally the master track meters (or the individual track meters if you are rendering stems), pre-sample rate conversion. As a result of this conversation we'll probably change the render meters to reflect the actual rendered file levels, post-sample rate conversion.

The bottom line is, your limiter is squaring off the peaks at the master bus, and sample rate conversion, by design and as expected, is restoring at least part of the missing peaks via interpolation.

As I wrote above, you have three choices if you want the rendered file under +0dB.

1. You can feed the master limiter at the rendered sample rate. I know you wrote the plugins "perform better at higher sample rates" but in this scenario, feeding the limiter at the lower sample rate is definitely a better result than feeding the limiter at a higher sample rate and then downsampling.

2. You can normalize. Normalizing does not change dynamics. No disrespect to Bob Katz but normalizing also does not introduce "distortion." The article you linked to is basically saying don't normalize because it's unnecessary, but in this case, it's necessary (unless you do #1 instead).

3. Lower the master fader, which is functionally equivalent to normalizing after rendering.
Got it...Makes sense. Thanks for the info! I'm just going to change the project sample rate to what I want to render at, and have it do pre-FX sample rate conversion.
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Old 08-16-2021, 06:57 PM   #10
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BTW, this is slightly beside the point but just as an observation -- if the limiter is squaring the peaks enough that sample rate conversion is restoring them by over 1dB, it's likely that the pre-sample rate conversion, limited signal sounds very similar to the post-sample rate conversion, clipped signal. To put it another way, the limiter is almost certainly introducing distortion before sample rate conversion.

Last edited by schwa; 08-16-2021 at 07:18 PM.
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Old 08-18-2021, 03:18 AM   #11
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Post SRC peaking is a known issue yes.
The best practice is to sample rate convert before applying the final true peak limited value you are after. You can render a SRC'd file in the "native" file samplerate by unticking the "process at project sample rate" button in the render window.
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