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ITU-R BS.412.9 Limiting OR Metering
https://forums.stereotool.com/viewtopic.php?t=4004		 Page 2 of 2
Author:  hvz [ Tue Feb 07, 2012 2:17 pm ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
BS412 update:
- Better (more constant) output
- Added an (optional) dynamic clipping level filter; if you turn this on the audio seems to get more stable. And it also contains a filter that reduces sudden very loud sounds, to avoid short loud kicks.

Winamp DSP plugin: http://www.stereotool.com/download/dsp_ ... 22-004.exe
Stand alone version: http://www.stereotool.com/download/ster ... 22-004.exe

IMPORTANT:
- Turn Bass Boost off! It increases the bass level, which has a huge impact on the BS412 limiter (normally, Loudness can handle it, but in case of BS412 the *measured* RMS level will greatly increase especially if there are very low bass sounds).

Suggested settings:
STS file: http://www.stereotool.com/download/Wolf5.sts
Then change:
- Enable BS412 limiting and Smart clipping
- Set Power Boost to +2 dB
- Set Input Ampl. to 0.74 (higher will cause more pumping, but also a slightly louder output).

Todo: I need to add a 2-band filter which reduces very loud highs. Without pre-emphasis the BS412 limiter works VERY well, with it it still has some issues with loud highs (the smart clipper helps a bit here).

Basically the loud highs (pre-emphasis) issue resembles the loud lows (bass boost) - but we cannot turn pre-emphasis off, unfortunately...
Author:  hvz [ Wed Feb 08, 2012 4:55 pm ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Now using a smart de-esser to reduce the problems caused by pre-emphasis. (No buttons or sliders added, it's not configurable - not yet anyway).

Stand alone: http://www.stereotool.com/download/ster ... 22-005.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-005.exe
Author:  hvz [ Thu Feb 09, 2012 3:55 am ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Made the de-esser configurable (set it to a higher threshold to keep more highs at the cost of getting bigger volume drops).
Added a separate window with a very large BS412 display (goes down to -12 dB).

Stand alone: http://www.stereotool.com/download/ster ... 22-006.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-006.exe

I ran over an hour of music (most of the torture test) through it without getting too much issues (2 brief volume drops to -3 dB), then I suddenly encountered one track that has around -4 dB throughout the entire track (Rihanna - Don't Stop The Music). It does not sound bad though. But I don't like it.

Except for this I think the filter is currently working very well.

Tested with the Wolf5 preset posted earlier in this thread, with these modifications:
- Enable BS412
- Set 'input ampl.' to 0.75x.

For the Rihanna track, I'll try tomorrow if I can do for bass what I did for pre-emphasis today.
Author:  hvz [ Thu Feb 09, 2012 4:18 pm ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Major redesign! (I know, I didn't see it coming either).

I've turned off most of the protection mechanisms that I had built in because they caused the audio level to drop occasionally (mainly when some silence would fall off at the other end of the 60 seconds). I'm now using only *1* method, which has far less impact on the sound. As it turns out, this does not only remove the big red line drops (which are followed by big compressor drops), but it also makes it possible to stay scarily close to the 0 dB line. I did have to add 0.05 dB of headroom for safety though... :shock:

Stand alone: http://www.stereotool.com/download/ster ... 22-007.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-007.exe

This should work with the Wolf5 preset that I posted earlier, I have now also tested much faster up and down times and that might be better.
Author:  hvz [ Sat Feb 11, 2012 6:12 pm ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Stand alone: http://www.stereotool.com/download/ster ... 22-008.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-008.exe

De-esser is less aggressive and should sound much better
Also a new preset: http://www.stereotool.com/download/wolf7.sts

Reason for new preset: Configured the AGC band 1 differently to allow less loud bass spikes (until now the bass band could get 150% louder than the center band, now that's reduced to 20%).


Adding an extra band for BS412 bass handling is probably still a good idea - will look into that next week.
Author:  hvz [ Tue Feb 14, 2012 6:03 pm ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Stand alone: WRONG COMPILE
DSP: http://www.stereotool.com/download/dsp_ ... 22-009.exe

Getting closer. In this version I see 2 problems:
- In some (rare) cases, the volume can drop too rapidly. Solution is knows, and I can probably implement it tonight.
- In some cases the volume goes up *way* too fast when the audio gets a lot softer. Most likely solution: Add gating.
Author:  hvz [ Wed Feb 15, 2012 9:35 am ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Stand alone: http://www.stereotool.com/download/ster ... 22-010.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-010.exe
Author:  hvz [ Thu Feb 16, 2012 10:49 am ]
Post subject:  Re: ITU-R BS.412.9 Limiting OR Metering
Stand alone: http://www.stereotool.com/download/ster ... 22-011.exe
DSP: http://www.stereotool.com/download/dsp_ ... 22-011.exe

BS412: Added some smoothing to the response speed and a new "sluggish rise" checkbox that can be set to avoid very sudden volume rises in the compressor.

The next update will be posted to the News section.
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