Problems to change format for webcam (linux)

Question

Hi,
in this forum i found Ownes JWebCam. The code is really great and it helped a lot. In this code he searchs for all supported formats with the method CaptureDeviceInfo.getFormats(). In the program he uses only the formats he found. I thought this is a good idea and coded it myself for my program. My problem is, that changing or setting the format myself doesn't work. I set the format with FormatControl.setFormat() and this method always return null, only the smallest format i find works.. I thought i made some mistake but i couldn't find one. After changeing Owens code for linux and runing the program, i found out, that the captured video is just scaled up and still uses the low resolution of the camera after changing it to 640x480 and the method setFormat() return null, too. With JMStudio i can use higher resolutions, so it must work with the camera. Has anyone some hints for me?
thx
markus

Answer 1

Hi,
i found the solution on my own in firm this morning.
For setting a new Format you first have to find all the supported formats with
Format[] formats = camInfo.getFormats().
camInfo is instance of CaptureDeviceInfo. After this i need a MediaLocator for my camera.
MediaLocator ml = camInfo.getMediaLocator()
With ml you have to create a DataSource with the Manager.
DataSource source = Manager.createDataSource(ml);
The next thing you need is a list of all FormatControls. I think you need this, because you need the correct FormatControl instance for the Format you want to set later.
FormatControl[] formatControls = ((CaptureDevice)source).getFormatControls();
Now you should have all you need to set a Format of your choice. Choose a Format out of formats[] you want to set. Save it in some variable. In this example i use the Variable myFormat. Now you have the Format you want to set. In the next step you have to find the compatible FormatControl for your wanted Format. To find it, you have to search the formatControls Array.
Format finalFormat = null;
for (int i = 0; i <formatControls.length; i++) {
if (formatControls[i] == null)
continue;
if ((finalFormat = formatControls.setFormat(myFormat)) != null)
break;
If formatControls[i].setFormat(myFormat) doesn't return null, you found the campatible formatControl for your Format and set the Format.
All you have to do now is to connect to the source, create a Player and do whatever you want to do with it.
Player player = null;
try {
source.connect();
player = Manager.createPlayer(formattedSource);
} catch (Exception e) {
e.printStackTrace();
I hope this will help anyone. Owens code (http://forum.java.sun.com/thread.jspa?threadID=570463&tstart=50) is really great and helps a lot, thanks for this, but i didn't find out how to change the resolution for the camera. Maybe i was just too stupid to find it :-) With Owens code i could solve all the other problems i had.
Have fun with this
Markus