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2012-08-27 09:47:17 -0500 asked a question CaptureFromFile - what does OpenCV exactly do?


My question is: What exactly happens under the hood in OpenCV when a video file is opened with CaptureFromFile and then RetrieveFrame is called?

In my particular case, I'm opening a H264 video file. When I call RetrieveFrame, I get decoded BGR images. But what exactly happens in between? I am using a Macports-installed OpenCV with Python bindings, so my intuition is that the decoding happens through ffmpeg. Is that correct? Is there documentation anywhere of the exact flow / calls that happen when CaptureFromFile / RetrieveFrame are called?



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2012-08-20 07:00:40 -0500 asked a question [Android - Native Camera] Setting ISO (and other camera parameters)

Is it possible to set camera parameters, such as the ISO, when using Android OpenCV's Native Camera?

When using the regular Android Camera, I can set the ISO using something like this:

mCamera =;
String[] supportedISOs = mCamera.getParameters().get("iso-values").split(",");

Then later

Parameters params = mCamera.getParameters();
// "choice" reflects the user's choice (ie. menu selection)
params.set("iso", supportedISOs[choice]);  

Though it is a bit of a hack - the ISO isn't exposed in the Android API like for example the WB, but it is still in the camera parameters on most phones. However, when using OpenCV's Native Camera, I don't know of a way to do something similar.

Is it possible? Are there plans to give access to the ISO and other parameters in the Native Camera (like the exposure time / shutter speed)?