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I wrote an android application that captures a live preview from the camera. It is important to have a short shutter time, which should at least be constant.

Currently I use the following code to achieve a low shutter time:

Parameters params = camera.getParameters();
params.setSceneMode(Parameters.SCENE_MODE_SPORTS);
params.setWhiteBalance(Parameters.WHITE_BALANCE_DAYLIGHT);
params.setFlashMode(Parameters.FLASH_MODE_OFF);
params.setFocusMode(Parameters.FOCUS_MODE_INFINITY);

params.setPreviewFpsRange(9000, 29453);
params.setPreviewFrameRate(29453);
params.setJpegQuality(100);
params.setPreviewFormat(ImageFormat.NV21);

params.setPreviewSize(1280,720);
params.setAntibanding(Parameters.ANTIBANDING_OFF);
params.setExposureCompensation(params.getMinExposureCompensation());
params.set("iso", 1250);
camera.setParameters(params);

The setSceneMode() seems not to be supported at my phones firmware (getSupportedSceneModes returns an empty list). The "ISO"-Setting has possibly no effect (have not looked at the picture, just calculated the frame rate, yet). Just found this code somewhere and used it... maybe it's just the wrong string?

What happens so far is: The frame rate changes between 9 and 29,453 fps, which is the only supported frame rate range. So params.setPreviewFpsRange(29453, 29453); doesn't work either. The Frame rate is high (20-30 fps) at good light conditions (normal day, indoors, directed to window) and becomes very low (8-10 fps) for medium/low light (daylight, indoors, direct away from window) conditions.

More in detail: I do not need a high frame rate, but a low shutter time. The gathered data shall be used for indoor navigation (or: Indoor Localization in a first step). The application needs to take pictures while a person is just normally walking, without the person caring about how he/she is carrying the phone. The person could be even running or "swinging" the phone (as you would normally move your arms when walking). So there is usually a lot of "motion blur", as soon the shutter time is too long. The situation is much different to "I want to make a photo" situations, where the photograph tries to hold the camera steady. We actually don't want to achieve "good photos", but want to somehow detect some edges of walls from time to time. I expect a lot of "noise" in the picture, but this is hopefully working anyway...

The Idea is, that there are possibly chances to get more control over camera parameters using the NDK. Has anyone experiences with the NDK and can answer me weather it's worth trying?

Additional Info: I'm using an HTC Desire Z (also named: "T-Mobile G2" or "HTC Vision") as test device.

BryanH
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SDwarfs
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1 Answers1

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The short answer is "NO". The longer answer starts with a question: your app does not care about the capture, but only uses the YUV preview frames, is that correct?

As a standard downloaded app with no root access, you have no permissions to access camera (or other) device directly. You only have setParameters() API to effect the camera behaviour, and thus you are completely at the mercy of the OEM as to what camera functionality is exposed through this API.

Even on a rooted device, your capabilities are limited, but now by the specs of the device drivers and specific camera ISP.

In both cases, you should start by very carefully choosing the target device. I believe that some Android phones allow much more camera control than HTC Vision. For example, a modified version of Samsung S2 http://pfittech.com/rom_pfittech_jb.html boasts stable 25 FPS at 1080p.

Alex Cohn
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  • I would like to avoid any unnecessary compression of the picture. Therefore the preview YUV-frames are fine. Even only a grayscale picture (Y-Layer) is ok. I have rooted the test devices. As its a research project, this is partially ok... but if I could avoid the need for root access, I would take it ;-). -- What do you mean by "modified version" (custom ROM?)... have some colleagues with a S2... maybe worth a try. – SDwarfs Sep 19 '12 at 07:28
  • Yes, the link points to a custom ROM for S2 tuned for highest performance. Anyway, for a research project, I would have searched for a device with most versatile/open camera, which HTC Desire Z is not. – Alex Cohn Sep 19 '12 at 07:42
  • OTOH, if I were you, I would not discard the **capture** route. Maybe it will produce better results for you. Maybe when you call `takePicture()` the "shutter" *(I put it in quotes because this is not a real shutter, but the effect of different factors of the Camera ISP on the motion blur)* will be shorter? You cannot get captured pictures at 30 FPS, but as you explain your algorithm, it may be fine to get relatively sharp images once a second. – Alex Cohn Sep 19 '12 at 07:47
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    Just tested my colleagues Galaxy S3. The "motion blur" of the preview in the normal camera app was a lot better (SceneMode: Sport). Only slight motion blur while "swinging" the phone. -- Will give takePicture() a try ... about 2-3 fps should be ok; I currently have to finish my PhD without financial support of my university, as the research project just ended. So I currently use my private hardware for it. I think about buying another smartphone for this... if this is actually needed and some premature results show usable results. – SDwarfs Sep 19 '12 at 17:26