Audio Capture on Pocket PC 2003

[Guest]

Hi,

I would like to capture audio, encode it, and stream it from one Ipaq to
another (pocket pc 2003). I have 3 questions relative to this problem.

1) I could not find any information about Audio Capture in my MSDN. What is
the simplest way to get the audio samples ? (i am working in C#, CF 1.0 SP3)

2) Is it possible to encode the audio samples using microsoft APIs ? if not,
do you know any third party APIs I should consider?

3) Do you think it would be a benefit to upgrade to .NET VS 2005 and Compact
Framework 2.0 Beta when it comes out next week ? I heard CF2.0 supports a
few functions of directX, that could be useful for audio capture?

Thanks a lot!

Lionel Reyero

 

[Peter Foot [MVP]]

1. You can wrap the native waveInxxx API calls - look at the
OpenNETCF.Multimedia.Audio namespace code for example
(www.opennetcf.org/sdf/)

2. Audio captured using the above method is encoded in PCM (.wav) audio.
What sort of encoding do you want? e.g. MP3?

3. There is no DirectX functionality in .NETCF v2.0, in fact there is
intrinsic audio functionality in .NETCF v2.0

Peter

 

[Guest]

Thanks Peter!

1. I'll take a look at it.

2. I would like to stream the audio data, so I am interested in codec with
low bitrates, such as G.729, do you know any ?

3. That sounds very interesting. Is there the full System namespace for CF
..20 on MSDN web site already ? I was looking for it a few days ago.
I downloaded framework 2.0 beta, can I install it and continue my project in
..NET studio 2003 without much problems ? or should I upgrade to VS 2005
beta ?

Sunday 11:30pm, and getting answers on newsgroup... it's awesome!
Thanks Peter!

Lionel Reyero

 

[Aziz Vasi via DotNetMonster.com]

Hi Lionel and Peter,
I am also working on a similiar program and I also am using C#.

1. For voice capture and playback I have investigated the Waveform Audio
Interface in the MSDN (http://msdn.microsoft.com/library/default.asp?
url=/library/en-
us/wcewave/html/_wcesdk_using_the_waveform_audio_interface.asp)
It seems interesting but it is a little complicated. I am now currently
investigating the audio API in the OpenNetCF.

2. I am also looking for an encoder/decoder which compresses the Wav sound
data into a smaller format suitable for VoIP. Any suggestions for codecs
are welcome.

I would also like to ask you are going to send and recieve the packets? Are
you going to use RTP protocol? I am also looking for a solution for this.
If you have any suggestions on how to send/receive real time data it will
be appreciated.

 

[Guest]

1) The OpenNETCF audio API is not very convenient for a VoIP application... I
am currently modifiying their source... it is not simple.

For RTP, I have looked for it, and I have not found any API for .NET, nor
for evc++... it seems that adapting a RTP Lib in C is the only solution. I
am considering implementing RTP myself in C#...

Lionel

 

[Chris Tacke, eMVP]

VOIP requires high throughput. I seriously doubt you'll be successful with
a pure managed code solution. A managed UI with native DLLs handling
streaming and playback would be viable, but I doubt doing the audio in
managed code will work.


--
Chris Tacke
Co-founder
OpenNETCF.org
Has OpenNETCF helped you? Consider donating to support us!
http://www.opennetcf.org/donate

 

[Aziz Vasi via DotNetMonster.com]

Thank you Chris,

For a VOIP application, would you suggest using the coredll.dll for
audio playback and capture? As a means for high throughput?

Do you have any suggestions for making an RTP Stack?
I am currently thinking of using the UDPClient in the System.Net. for
sending the voice bytes. Do you think that will give a high throughput?

PS: My VOIP application needs to have full-duplex capabilities.


Thank you for your answers,

Aziz

 

[Guest]

Hi Aziz,

You can use the Waveform Audio Interface (what uses OpenNETCF). You should
take a look at this page, and download their sample
http://msdn.microsoft.com/mobility/default.aspx?pull=/library/en-us/dnnetcomp/html/waveinout.asp

I have trouble with it and full dublex. I started a topic about it, you can
read it here:

http://msdn.microsoft.com/newsgroup...mobile-wince&lang=en&cr=US&sloc=en-us&m=1&p=1


Lionel,

 

[Guest]

Hi Aziz,

For the audio capture and playback look at
http://msdn.microsoft.com/mobility/default.aspx?pull=/library/en-us/dnnetcomp/html/waveinout.asp
It is a great example, I find it better than the OpenNETCF Audio stuff, it
is easier to customize.

I'am having troubles with full duplex, you can read the topic I've started
about it here
http://msdn.microsoft.com/newsgroup...&tid=a58d106c-5e37-4858-8092-28266aebdf2e&p=1

Lionel Reyero