Larmit..

Please see the attached zipped VB6 project. The code is thoroughly commented so hopefully should be easy to use...

The pre-compiled exe was compiled on a Win98SE system and because of the nature of the API used (winmm.dll) you will need to compile it again if the target system is NT/W2000/XP.

If it doesn't run as expected, I can do a version for you with lots of diagnostics in so we can see at which point it is failing.

Don't forget that this works by putting the sound driver in record mode, so you'll need to set up the Windows audio recording mixer to actually give you an input..

Let me know how you get on.

Usual disclaimers apply about this developmental software...

Regards
Alan

Hi Soorya!

I did some work on this myself because I needed an 'automatic level control' for an mp3 based disco application I was writing, and wanted to to equalise the level at which different mp3 files played. As I understand it, audio/video- it makes no difference as far as the way the sound is handled is concerned.

As for the answer, here's a few pointers:
VU meters (in sound card terms) aren't a good idea as they aren't implemented in any standard way on different cards and some low end chip sets don't have them at all. With these, what you get is a 'snapshot' of the sample values at regularly repeating intervals. When this is displayed on a bar graph, the peak value the samples get to is visible by persistance of vision. This is really all the usual displays (like on the Windows mixer) do. However, it's neither a 'VU meter' in the true sense of the word nor a measurement you can export without some additional maths. The sound card VU meter gives a 16-bit number where 16383 is 'zero' and 0 and 32767 are positive and negative max. respectively. See what I mean?!

Incidentally, a true VU meter is logarithmic and has defined attack and decay times.

Controlling the volume sliders in the sound card is difficult. There is a lot of API programming and it's necessary to enumerate the sources, destinations, 'controls' and 'lines' in the sound card, and their names and capabilities, to sort out what is what.
The following link is to a VB5/6 project that is a vaulable development tool for anyone playing with audio, it enumerates and displays all of the facilities in the card.

http://www.shrinkwrapvb.com/mixer.htm

The good news is, once you've been through the grief of identifying the control you want to change, writing a new value to it (a 16 bit number between 0 and 32767) is easy enough.

Here's some pitfalls:
Some of the DirectX controls seem to bypass part of the sound card, or do their D/A conversion in a different way, so that VU meter on the wave out line doesn't work. An example of this is using msdxm.ocx to play an mp3.

I hope this helps. I might write a tutorial on using audio if I ever get time...

Regards, AlanC

Soorya,

Please try the project attached below. It's a VU meter using the principle I worked on for level detection, i.e. it puts the sound card in record, grabs samples, and measures them. Its all VB6 with no 3rd party controls.

This works even using DirectX components for play, but will only work if your sound card's full duplex (most are now aren't they?) You'll need to select 'wave' on your recording mixer as the source.

This is a first stab attempt and I roughly calibrated it to 0dB full scale with a given level setting but it'll depend on your system. Attack/decay timing will depend on the speed of your computer. As it's logarithmic even tiny signals and any noise or offset will give a slight reading with no sound.

I also have a tone generator app for calibrating such things if you need it.

Take care and have a good Christmas.
AlanC