Stereo Tool

Hi,

First, sorry for my bad English.
We spoke about it in an e-mail discussion, and i think, that's a good idea. So, i think, that it's a helpfully extra for radio stations in Europe.
We have in Hungary 4dB Power MPX limit, and if we can that showing or monitoring, than the Stereo Tool makes our sound better.

Thanks, and i wait for reply.
Gábor Bajáki
Rádió Smile

Just this morning I got a new idea to implement it. I have 'brainstormed' a bit about it with Leif Claesson a few months ago, and we both thought that it would be difficult. But this morning I suddenly realized something: Normally you will configure your radio station such that you're getting close to (or slightly over) the ITU-412 maximum levels, and the only thing you need the protection for is to push the level down slightly if you are just going over the maximum.

Before we were considering more extreme situations.

For this milder implementation, I think I have a solution that I expect will take only a few days to implement. I don't think I'll have time for it this year, but I want to look into it asap in January.

Is there anyone here who can measure if a .WAV file with MPX data complies to BS412? Just to make sure that I understand the standard correctly...

Here's a BS412 limited file (I hope). Quite bad pumping, still working on that... (It helps a lot to allow about 0.3 dB more headroom, but I wanted a loud file to check for compliance).

http://www.2shared.com/audio/_5FSk6sI/o ... -_x14.html

This download site doesn't seem to work. I guess it's a scam or something (I searched for a site where I could upload *big* files and this one came up).

Will try again later - the sound has gotten much better since yesterday so I could just as well upload a new version now.

Hans, the link is working, is a little slow but it works

_________________
by GAP
"Less is More" (Bob Katz)

Note: There is already someone in Germany who has proper test equipment who will test this version. So there should be no need to test this for others...

But if you really want to:


http://www.stereotool.com/download/radi ... 12TEST.exe

Use with this preset:
http://www.stereotool.com/download/WOLF_BS412.sts

Then make the following changes (make sure that audio has been running BEFORE doing this or you'll get a lot of static, there's a bug somewhere):

1. Load the attached preset.
2. Go to the Loudness window
3. Enable "BS412"
4. Set "Power Push" to +2 dB
5. Set "Input ampl" to x 1.50

For tracks with a very constant level, the level may drop far too much
after a while, I still have to fix that (it helps to lower "Power Push",
but then you won't get as close to 0 dB).

This version also creates a log file in C:\temp\st.log (assuming that
C:\temp exists and is writable), this file contains the values that Stereo
Tool calculates as the MPX level. If something is wrong it might be useful
for me to compare the two.

Hey everyone,

I got the measurement results back and it looks promising. There were indeed huge gaps in the audio (much worse than I had expected), but the peak level seems to be ok.



This new version has less gaps (not completely fixed yet, but the worst case gap that I measured was -12 dB before, now it's -2 or -3). In music I haven't seen anything below -0.8 dB yet.

http://www.stereotool.com/download/radi ... EST002.exe

Works with the same settings as before.

Worst case gap is now down to -0.8 dB. This version is probably good enough to put on the air, although it needs to be tested more.

http://www.stereotool.com/download/radi ... EST003.exe


Next steps:
- Add some sliders for some controls that I added today (level drop shape)
- Add a display so you can actually see what the limiter is doing, and if you need to adjust it (configuring is nearly impossible without this, so far I've been using the log file for this).

Sliders and display added!

Stand alone: http://www.stereotool.com/download/radi ... EST004.exe
Winamp plugin: http://www.stereotool.com/download/dsp_ ... EST004.dll

input ampl. must now be set to 0.75 instead of 1.50!

Next steps:
- Automatically enable Loudness filter at the proper settings
- Add a bigger display for larger time intervals (1 hour and esp. 1 day are too small to clearly see what's happening)
- Make it work also when no FM output is generated


Usage is still the same as before, but you need to set 'input ampl,.' to half the value you needed to set it to before (so 0.75 instead of 1.50).

The display shows a BLACK bar with the 60-second output level, and a RED bar that drops down when the target output level is reduced - this happens when continuing with the output as it is would cause overshoots. Too much drops of the red bar causes gaps as you have seen in the first version; drops of about 1-2 dB and occasionally slightly more are acceptable (in the first version there were drops to below -12 dB!).

Drops of the red bar are caused by the 'power push' setting, if it's set to 0 dB you should get no red drops. The drops usually don't get (much) bigger than the 'power push' setting, so with power push set to +2 dB it should not get much lower than -2 dB.

The 'volume drop power shape' slider controls how quickly the red bar drops if overshoots will occur if the current signal continues. At ^1.00 it will drop in a straight line, higher values cause a curve that starts to drop at a faster rate. The advantage of this is that - because the dropping starts faster - less loud sounds are inserted at the start, so it doesn't have to drop as far. On the other hand, if you have short bursts of louder sounds the disadvantage is that those bursts are lowered in volume more quickly.