I'm trying to get a stable frame rate from a simple camera Android application written based on the guide below.
http://developer.android.com/guide/topics/media/camera.html - Non intent version.
There is only preview and there is no image or video capture. Everytime onPreview (implementating previewcallback) is called, I check timestamp differences to measure frame rate. Though on average it meets the 15 FPS rate I set ( setPreviewFpsRange(15000, 15000 and verified that it is supported on the device using getSupportedPreviewFpsRange() ), the individual frame rate vary from 5 fps to 40 fps.
Is there a way to fix this. What are the reasons for it? Guess one reason is application process priority. It was observed that adding more applications reduced the fps. One solution is to increase priority of this camera application. Second reason could be garbage collection and slow buffer copies to preview. Third reason is that camera api (not the new camera2 api of Android L - my device is not supported yet) was not designed for streaming camera data.
Also the exposure time lock was enabled to fix frame rates.
It's most likely just how you are timestamping the frames. Try saving a sequence of preview frames pointed at a stopwatch to disk and viewing them using a YUV player (i.e http://www.yuvtoolkit.com/).
Related
I am working with a Qualcomm Snapdragon processor with a periphery camera. The project I am working on needs to process the frames from the camera with OpenCV as quickly as possible. In order to verify that things are working, I would like to know the output fps achieved and also the input fps to see how many frames are being skipped. Is there a way to see how many frames per second the camera is providing to the processor? It should be able to work in the general case, for any input camera.
I've looked through the Camera2 API a bit, and found the parameter SENSOR_FRAME_DURATION, but I am not quite sure how to access it. Also, I am using JavaCameraView, which seems to act as a bridge between Camera and OpenCV. Any advice would be appreciated.
I'm getting frame rate calculated as below. In your onCameraFrame method you can measure the time taken between 2 consecutive frames.
prevTime = time;
time = SystemClock.elapsedRealtime();
Frame rate= (1000 / (time - prevTime))
When setting manual controls in Android by using the Camera2 API, what is the purpose of CaptureRequest.SENSOR_FRAME_DURATION?
I have read several times the documentation but still can’t understand its purpose, and what value to set in relation to the exposure time and ISO.
I understand the CaptureRequest.SENSOR_EXPOSURE_TIME specifies how much light is the sensor letting in; also that the CaptureRequest.SENSOR_SENSITIVITY is the sensor sensitivity to light (ISO), but no idea about SENSOR_FRAME_DURATION and how it relates to the exposure time and sensor sensitivity.
For example, if I set a long exposure time of 1 second or 30 seconds, then what is the value that I should set in SENSOR_FRAME_DURATION? And how does it relate to the other sensor controls?
FRAME_DURATION is the same concept as output frame rate. That is, how often is an image read out from the image sensor? Frame rate is generally reported as frames per second, while FRAME_DURATION is the inverse of that - the duration of a single frame.
Since the camera2 API is all about per-frame control, having the duration as a per-frame property is appropriate.
FRAME_DURATION can't be shorter than EXPOSURE_TIME (since you can't read the image from the sensor until exposure is complete), but the API handles this for you - if you ask for a FRAME_DURATION that's too short compared to EXPOSURE_TIME, it gets automatically increased.
That said, often you may want consistent frame rate (such as 30fps for video recording), so you'd set your FRAME_DURATION to 1/30s = 33333333 ns, and then vary EXPOSURE_TIME for manual exposure control. As long as you keep EXPOSURE_TIME as less than 1/30s, you'll get steady frame rate and still have manual exposure control.
The minimum possible frame duration (and therefore the maximum frame rate) depends on the output resolution(s) and format(s) you've asked for in the camera capture session. Generally, bigger resolutions take longer to read out, putting a limit on minimum frame duration. Cameras that support the BURST_CAPTURE camera capability can handle at least 20fps for 8 MP captures, or better.
At the image sensor level, frame duration is implemented by adding in extra vertical blanking time so that EXPOSURE + VBLANK = FRAME_DURATION. The full picture is also more complicated in that typical CMOS image sensors can be exposing some rows of the image while others are being read out (rolling shutter) so the actual timing diagrams look more complicated. You don't generally have to care when just doing basic manual exposure control, however.
Most of the image sensors in a smart phone are using rolling shutter, which readout pixels line by line, the FRAME_DURATION = FRAME_READ_OUT_TIME + VBLANK.
I want to fix the frame rate of camera preview in Android, i.e., 20fps, or 30 fps. However, we find the frame rate is unstable.
In the android document, it is said that the frame rate is fluctuated between the minimum frame rate and the maximum one which are defined in getSupportedPreviewFpsRange.
https://developer.android.com/reference/android/hardware/Camera.Parameters.html#getSupportedPreviewFpsRange%28%29
My questions are:
1) Which factors influence the frame rate? exposure time, white balance, frame resolution, background CPU loading, and etc.?
2) Is there any method to fix the frame rate by customised above factors?
3) In my project, higher frame rate is better. If the frame rate is unstable in the end. Can I increase the minimum frame rate? or fix the minimum frame rate?
4) It seems that the video taking is somewhat different with preview model, Can I fix the frame rate or minimum frame rate of video taking in Android?
Finally, we found that IOS can fix the frame rate using videoMinFrameDuration and
videoMaxFrameDuration.
Thanks.
First of all, please note that the camera API that you ask about was deprecated more than 3 years ago. The new camera2 API provides much more control over all aspects of capture, including frame rate.
Especially, if your goal is smooth video recording. Actually, the MediaRecorder performs its job decently on older devices, but I understand that this knowledge has little practical value if for some reason you cannot use the MediaRecorder.
Usually, the list of supported FPS ranges includes fixed ranges, e.g. 30 fps, intended exactly for video recording. Note that you are expected to choose a compliant (recommended) preview (video) resolution.
Two major factors cause frame rate variations within the declared range: exposure adjustments and focus adjustments. To achieve uniform rate, you should disable autofocus. If your camera supports exposure control, you should lock it, too. Refrain from using exotic "scenes" and "effects". SCENE_MODE_BARCODE and EFFECT_MONO don't seem to cause problems with frame rate. Whitebalance is OK, too.
There exist other factors that cause frame rate fluctuations that are completely under your control.
Make sure that your camera callbacks do not interfere with, and are not delayed by the Main (UI) thread. To achieve that, you must open the camera on a secondary HandlerThread. The new camera2 API makes thread management for camera callbacks easier.
Don't use setPreviewCallback() which automatically allocates pixel buffers for each frame. This is a significant burden for garbage collector, which may lock all threads once in a while for major cleanup. Instead, use setPreviewCallbackWithBuffer() and preallocate just enough pixel buffers to keep it always busy.
Don't perform heavy calculations in the context of your onPreviewFrame() callback. Pass all work to a different thread. Do your best to release the pixel buffer as early as possible.
Even for the old camera API, if the device lists a supported FPS range of (30, 30), then you should be able to select this range and get consistent, fixed video recording.
Unfortunately, some devices disregard your frame rate request once the scene conditions get too dark, and increase exposure times past 1/30s. For many applications, this is the preferable option, but such applications should simply be selecting a wider frame rate range like (15, 30).
I'm trying to use the camera for video processing that needs a high constant frame rate around 30 FPS.
I'm using the Camera class and setPreviewCallbackWithBuffer to receive the video frames. I have noticed that most camera does not support a FPS range of 30000 - 30000. However, when recording movies I assume the camera on those devices still delivers a frame rate around 30. Is there some other way to achieve a higher frame rates than with my current method?
Note that non-top devices with cheap cameras, especially front ones, don't support reliably fps you've requested. If you request 30, device can reply ok (will start capture, no crash, etc) but in real it will deliver frames with fps in range say... [4-30] depending on lighting conditions (less light needs longer exposition time) and may be something else too. Example of such camera is front camera on galaxy S3 mini
If you don't want to use static fps rate for all the devices, you can use getSupportedPreviewFpsRange () method to determine the available fps range for that particular device. This method will return minimum and maximum supported fps rate.
Now after getting the maximum supported fps rate, you can use your current method to set the fps rate.
Hope this will give you some hint about setting fps to its maxmimum.
I have an application streaming video from the device to a remote computer. When trying to set the frame rate I keep getting:
ERROR/StagefrightRecorder(131): Failed to set frame rate to 15 fps. The actual frame rate is 30
The code I use is:
video = new MediaStreamer();
video.setVideoSource(MediaRecorder.VideoSource.CAMERA);
video.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
video.setVideoFrameRate(frameRate);
Any ideas on how to fix this?
The decoders usually come from the semiconductor vendor like TI, Qualcomm etc. It depends on the decoders whether they honor the call of frame rate modification or not. From the app layer, you cannot do much on this. The calls that you are making are the right ones. If the underlying decoders support it, then you can modify else you cannot.
Vibgyor
I guess documentation says that you may or may not be able to set the frame rate from the application layer. It depends on the underlying decoder whether it gives the app that flexibility or not. I wagely rememeber that I ahve tried setting frame rate to even 3-4 frames but still it gives the default frame rate only. I have seen in the Stagefright framework that it passes the frame rate call to the decoder and then depends on the deocoder to honor the call or not.
Vibgyor