Android :: Get Preview Size / Bad Result On Froyo Emulator

I was trying to use some of the new camera methods included in Froyo, i.e. setPreviewCallbackWithBuffer() & addCallbackBuffer(). In the documentation it's said you need first to create a buffer of appropriated size and use the addCallbackBuffer() method. The buffer size must be width * height * bits_per_pixel or otherwise you'll never receive a preview frame. To know the image size, you can ask to the camera about it's configuration. When I'm trying to configured the camera I use Camera.getParameters().getPreviewSize() the emulator says the size is 320*240, but with that size it didn't work on emulator. I used the old setPreviewCallback() and, in the onPreviewFrame(), I asked the size again. That time the size was 480*320. Then I hard- coded that values in the first code and everything worked. Now I'm afraid not only the emulator would have that behavior. Unfortunately I don't have any real device with Froyo and I can't try it. So, anyone have tried that methods in real devices? btw, are they really increasing the poor performance and frame rate?