Normalizing MP2 with BeSplit ends up clipping

[colorbars]

I've been around and around this and I can't figure it out. I'm hoping someone here can help.

I'm trying to normalize MPA/MP2 files that were created with a Hauppauge WinTV PVR USB2 from a cable box using the baseband (RCA) inputs. The audio level is very low on the recording, so I'm trying to normalize using BeSplit with this command line.

c:\besplit\BeSplit -core( -input %1 -output normalized-%1 -type mp2 -logfile besplit.log ) -ota( -G max )

This is what I get in the log.

BeSplit v0.9b6 by DSPguru.
--------------------------

Logging start : 12/09/07 , 22:36:05.

c:\besplit\BeSplit -core( -input blueharvestseg.mp2 -output normalized-blueharvestseg.mp2 -type mp2 -logfile besplit.log ) -ota( -G max )

[00:00:00:000] +------- BeSplit -----
[00:00:00:000] | Input : blueharvestseg.mp2
[00:00:00:000] | Source Sample-Rate: 48.0KHz
[00:00:00:000] | Channels Count: 2, Bitrate: 384kbps
[00:00:00:000] | Output : normalized-blueharvestseg.mp2
[00:00:00:000] +---------------------
[00:01:31:872] | Asserted 18.3dB to normalized-blueharvestseg.mp2.
[00:01:31:872] +---------------------
[00:01:31:872] Operation Completed !
[00:00:01:000] <-- Process Duration
Logging ends : 12/09/07 , 22:36:06.

The problem is that the volume level ends up so high that it clips. I just can't figure out why. Other people seem to use that same command without a problem. I can run the same file through BeSweet and have it normalized properly, but that involves transcoding which I don't want to do. Any ideas?

[Soopafresh]

Try this:

mp3gain /f /s s /d 100 /k /r yourfile.mp2

[colorbars]

Unfortunately it really is an mp2 file, so mp3gain chokes on it.

Thanks though.

[AlanHK]

If automatic normalising fails, do it "manually".

I wrote this little batch file.
save as MP2up.bat

Usage: MP2up audiofile.mp2 gain
Where "gain"is the gain in dB.
It will create a new file with volume boosted by "gain".

@if %1A==A goto usage
c:\besplit\BeSplit -core( -input %1 -output up%2dB--%1 -type mp2 ) -ota( -G %2dB )
goto end
:usage
@echo MP2up audiofile.mp2 gain (dB)
:: MP2 file %1 gain = %2 dB
:end

Since "max" was too much, at 18.3 dB, try, say, 10.


Also, I think MP3DirectCut can handle MP2s, and can boost or normalise volume losslessly.

[colorbars]

Doing it manually is an option, but trying to get it "right" is a challenge.

Checked mp3directcut and it says it can't change the volume on layer 2 files.

Thanks for trying.

[Soopafresh]

Then just decode it to WAV and you'll have a slew of different methods to normalize it. You won't lose much quality. Besides, it'll sound much better than it does now.

[AlanHK]

Doing it manually is an option, but trying to get it "right" is a challenge.
Checked mp3directcut and it says it can't change the volume on layer 2 files.
Thanks for trying.

Sorry about MP3directcut. But the batch file MP2up I posted certainly does work though.
Take two or at most three guesses and you'll get the right volume.
The reason I worked it out was finding so many files that had obviously been automatically normalised, leaving important sections (like speech) too quiet to allow for noisy sections (like explosions) not to distort.

The only automatic normaliser I trust is MP3Gain. I fact, I sometimes convert batches of audio to MP3 just to let MP3Gain analyse them, then delete the MP3s and apply the gain values on the source files. If only there was an AC3Gain...

[lordsmurf]

I only normalize in SoundForge, don't trust Besweet.

[Midzuki]

I would open the source audio in Goldwave/SoundForge/Audacity,
normalize it, save as .wav, compress with toolame.

+++++

[colorbars]

In doing some more tests I figured something else out. The problem is in the math that BeSplit is using to recalculate the volume levels. When I decompress and normalize in Goldwave, the recommended change in dB is about .5 above what BeSplit says it will be adding to the same file. The Goldwave normalization sounds perfect. So it seems like BeSplit is adding more volume to the file than it should be. I'm running WinXP SP2. I tried running the DOS box in compatibility mode (both Win95 and WinNT) and that didn't affect anything. I also tried running it on another machine (also WinXP SP2) and it gave the same result. Maybe such a large change (around 18 or 19 dB) is just too much for it to handle?