Main features

• Can I connect through NAT/Router or a firewall?
• Is multicasting supported?
• What is the underlying API used in the VCX library?
• Can I record from any of the input devices listed in the Windows audio control panel?
• Is it possible to use VCX library on a web page?
• Do your VCX library supports MP3 format?

Licensing and registration

• I can't apply a Developer license registration key on Windows Vista

Technical details

• My applications work fine from the VB IDE. However, in the compiled program no events are fired
• How could I receive a list of FormatTag property values?
• Why are lots of audio packets skipped when transferred through the network?
• The component can't be switched to a stereo mode
• Server and Client sends/receives bytes but there is no sound yet

Can I connect through NAT/Router or a firewall?

Generally our VCX library requires direct connection between two peers for streaming to be possible.

If your NAT/Firewall is configured properly, it should also be possible to connect through it. All you need to make sure is that NAT allows connection on specific UDP or TCP port to be made from local client (located behind the firewall) to remote server (located in the Internet).

Moreover, the server machine could also be located behind the NAT/Firewall, and client from Internet still can make a connection to it. Again, if NAT supports this and is configured properly.

Is multicasting supported?

No, only broadcast sockets are supported.

What is the underlying API used in the VCX library?

ACM and MME.

Can I record from any of the input devices listed in the Windows audio control panel?

We have a component for recording live audio from any installed sound card in any supported format. All you have to do is to place the vcproxWaveInX component on a form, specify the pcm_XXX properties and activate it by setting active property to true.

If you wish to save recording in a WAV file, simply link the above component with our vcproxWaveRiffX component. You can refer to our WaveRec demo, located in "demos\c#\WaveRec\" folder of VCX installation for example.

Is it possible to use the VCX library on a web page?

Yes, we have an example of how you can integrate our VCX library into a web page. Please refer to the "demos\web\mgclient.html" HTML page for more details.

Do your VCX library supports MP3 format?

If your system have MP3 ACM codec installed, you can produce and playback WAV files with MP3 stream inside. It is also possible to stream directly in this format. Switch codec-dependent components into MP3 mode by setting their FormatTag = 85.

We are also planning to add support for third-party libraries such as Lame or BASS in future updates.

I can't apply a Developer license registration key on Windows Vista

Since the VCX library saves a registration key in Windows registry, you need to start your application via "Run as administrator" on Windows Vista. Otherwise, it will keep on asking you a registration key over and over again.

This problem doesn't issue the Enterprise license which allows you to apply your registration key during your application setup process.

My applications work fine from the VB IDE. However, in the compiled program no events are fired

This is applicable for VB 6.0. VS.NET applications are not affected.

If you are using event handler for any of our components, please make sure that SyncEvents property is set to True for all components with event handlers.

How could I receive a list of FormatTag property values?

You can find the full list of numbers in regmm.h file from Platform SDK, or in the MSDN Library. Please also note that only limited number of codecs listed there are usually installed on a system by default.

To see which codecs (with their numbers) are installed on your system try this program. Redirect the output to a file name to review the results:

acmEnum > codec.xml

Why are lots of audio packets skipped when transferred through the network?

Ensure that you have enough bandwidth for the quality you want to achieve or decrease the quality settings (PCM... properties values). Each codec has own compression ratio. For GSM codec (FormatTag = 49) the ratio is 1:10, for ADPCM (FormatTag = 2) it is 1:4. Uncompressed CD Quality stream requires a bandwidth of about 200 KB/sec. Also, you may try to increase the OverNum property value, which represents the buffer size. This makes sense in WAN that may group a number of packets before sending them out to the air, so receiving side should be prepared to receive all of them at once.

The component can't be switched to a stereo mode

GSM codec which is used by default in our examples (FormatTag property is set to 49) do not support stereo streams, so you should try ADPCM or even MP3 codec instead.

Server and Client sends/receives bytes but there is no sound yet

Most likely the server side is not recording any audio signal. Please make sure you have selected the proper recording source for it. Double click on the Volume icon is System Tray, select Options - Properties, select Recording radio button, press OK and check which recording line is currently selected.