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    Invelos Forums->DVD Profiler: Plugins Page: 1  Previous   Next
Tool: MonoCheck
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DVD Profiler Unlimited RegistrantStar ContributorGSyren
Profiling since 2001
Registered: March 14, 2007
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Sweden Posts: 2,967
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My search for a way to determine if 2-channel audio track is mono or stereo led me pretty much nowhere, so I decided to try to write a program to help. The result is MonoCheck.
(Yes, it's that small!)

It compares the left and right channel of the audio output from your PC when you play a movie at a normal volume. It can determine if a track is actually mono.

You can read all about it in the online help.
My freeware tools for DVD Profiler users.
Gunnar
DVD Profiler Unlimited RegistrantStar ContributorGSyren
Profiling since 2001
Registered: March 14, 2007
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Sweden Posts: 2,967
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If it wasn't clear why I thought we needed a way to identify 2-channel mono, here it is.

From the Audio section in the rules:
Quote:
Note: Select Mono for both 1-channel and 2-channel mono.


Media players seem to always report 2-channel audio as stereo, which leads to a lot of profiles, especially for older movies, having the wrong information.

When in doubt - MonoCheck

PS For a brief moment I considered calling the program The MonoLisa, because it's a masterpiece. 
PPS Do read the help file before contributing! It really holds important information.
My freeware tools for DVD Profiler users.
Gunnar
 Last edited: by GSyren
DVD Profiler Unlimited RegistrantStar ContributorGSyren
Profiling since 2001
Registered: March 14, 2007
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Sweden Posts: 2,967
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I found that the "noise" level limit for the prediction needed a bit of tweaking.
Stereo tracks with very limited stereo effects could be reported as M2 (2-channel mono).
You would still see the values changing, so you should realize that it's probably not mono, but still ...

Fixed in MonoCheck 1.0.1
My freeware tools for DVD Profiler users.
Gunnar
DVD Profiler Unlimited RegistrantStar ContributoriPatsa
Zzzzzzz
Registered: March 13, 2007
Sweden Posts: 2,965
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Nice tool!

For additional visual verification you could also try this: Soundcard Scope

I haven't tested it on DVDs but it works well enough comparing mono and stereo tracks on Spotify, for example with The Beatles "1" (Remastered).

For older recordings you will sometimes see variations in the input signals due to channel noise but the differences are generally much smaller than for real stereo.
Patrik
DVD Profiler Unlimited RegistrantStar ContributorGSyren
Profiling since 2001
Registered: March 14, 2007
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Sweden Posts: 2,967
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For those who are interested.

How it works in detail

MonoCheck uses a .Net audio library called NAudio in order to monitor the output from the PC's soundcard. This gives MonoCheck a floating point value for the left and right channel, and it computes the difference between these two values.

In theory, if the sound is mono there should be no difference, so the value should be zero. If it is 1-channel mono, then it probably is zero, unless the sound card introduces changes in the audio streams. If it is 2-channel stereo, then we have two separate channels encoded on the disc, and the encoding may introduce some slight variations, especially if it is not a lossless encoding.

So, a standard Dolby 2-channel mono track will definitely have some very minor differences. A stereo track will have much larger differences, but it will still be a very small value. What MonoCheck attempts to do is to magnify that value to the point where the integer part is still zero for a mono recording, but well above zero for a stereo recording. That way, the user should be able to see the displayed value stay at zero when it is mono, and vary quite noticeably when it is stereo.

Internally MonoCheck also keeps track of the highest raw value of the difference, in order to determine with some degree of accuracy if the track is 1-channel mono, 2-channel mono or stereo.

So, there are two things that has had to be determined by trial-and-error; the multiplier for the displayed value, and the threshold for the raw value. This means that MonoCheck is probably not 100% perfect, and may never be. But it should still be good enough to give a reliable result.


Currently the magnifier still seems to need a little tweaking. I have noticed that mono tracks may "spill over" and occasionally display 1 instead of 0. But that should not be enough to fool anyone into thinking that it is stereo. Stereo shows much larger values.

If anyone has a PC setup with more than 2 audio channels, for example 5.1, I would very much like to know if MonoCheck works there as well. I have not been able to test that.
My freeware tools for DVD Profiler users.
Gunnar
DVD Profiler Unlimited RegistrantStar ContributorT!M
User since 6 Dec. 2000
Registered: March 13, 2007
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Brilliant tool! 
DVD Profiler Unlimited RegistrantFrodonf
Registered: March 14, 2007
Canada Posts: 225
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Wow!
Great tool!

Thanks GSyren 
Certainty of death...
Small chance of success...
What are we waiting for ?!
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