I want to capture video without showing a preview. The android docs here say this is possible, but don't explain how:
http://developer.android.com/guide/topics/media/camera.html#capture-video
Note: It is possible to use MediaRecorder without creating a camera preview first and skip the first few steps of this process. However, since users typically prefer to see a preview before starting a recording, that process is not discussed here.
what are the "first few steps" to skip?
Thank you
You misinterpret the documentation. What it really says (emphasis mine):
It is possible to use MediaRecorder without creating a camera preview first and skip the first few steps of this process. However, since users typically prefer to see a preview before starting a recording, that process is not discussed here.
In other words, you can create a preview and immediately start recording. There is no hint that MediaRecorder will let you run a hidden recording session.
Moreover, I agree with the document that the added value of not starting preview before starting recording, is negligible.
You can just skip step 5 of configuring media recorder given in the above link and preview wont be shown. But user will be interested in viewing its preview.
Even though the documentation states it is possible, most of SO answers say otherwise. Take a look at this answer (and the answers linked in it).
The work around this limitation is to create a 1 x 1 px SurfaceView and use it to display the camera preview.
Related
I want to image process android front camera frames inside a service.
I use OpenCV and therefore using CameraBridgeViewBase which asks for camera view.
I dont want to record the video. i need to process each frame in real time.
any solution ?
According to the examples of fadden available (have a look here), you can do it using a SurfaceTexture instead of a SurfaceView for getting the frames. It was also answered here before, but unfortunately never validated.
I could get frames from a service this way.
I wrote a small game. It has a front facing cam preview implemented. I want to be able to record the entire screen to a mp4. How would I do that? Anyone know a nice tutorial for recording the entire screen to mp4 (in code, so not just screenshots.. I want to enable the user to make a recording, while playing the game).
Indeed, as #Michael stated, directly accessing the screenshot and framebuffer mechanisms is not possible. That doesn't mean you're completely out of luck, though, if you want to record gaming sessions. It's just more work.
If you generate a perfect record of the various actions in your game, save that record. You can then build a service (web service, local, whatever) that accepts the record as an input. In effect, it would replay the game. You'd then reconstruct the game in such a manner that you could generate a video.
You could also replay in the Android emulator and create a video from that. Not as easily deployable, but it depends on what you want to do with it.
Apps aren't allowed to grab the screen contents (see this discussion).
[L]etting applications grab the screen's content liberally is a serious security risk, which is why the platform prevents it (taking a snapshot requires either direct physical manipulation from the user, or using a debugging tool).
And as #CommonsWare mentioned in his comment you can't use the getDrawingCache method either to grab a Bitmap of the View if you're using a SurfaceView or one of its children (e.g. VideoView). More details about that here.
I want to write an activity that:
Shows the camera preview (viewfinder), and has a "capture" button.
When the "capture" button is pressed, takes a picture and returns it to the calling activity (setResult() & finish()).
Are there any complete examples out there that works on every device? A link to a simple open source application that takes pictures would be the ideal answer.
My research so far:
This is a common scenario, and there are many questions and tutorials on this.
There are two main approaches:
Use the android.provider.MediaStore.ACTION_IMAGE_CAPTURE event. See this question
Use the Camera API directly. See this example or this question (with lots of references).
Approach 1 would have been perfect, but the issue is that the intent is implemented differently on each device. On some devices it works well. However, on some devices you can take a picture but it is never returned to your app. On some devices nothing happens when you launch the intent. Typically it also saves the picture to the SD card, and requires the SD card to be present. The user interaction is also different on every device.
With approach 2 the issues is stability. I tried some examples, but I've managed to stop the camera from working (until a restart) on some devices and completely freeze another device. On another device the capture worked, but the preview stayed black.
I would have used ZXing as an example application (I work with it a lot), but it only uses the preview (viewfinder), and doesn't take any pictures. I also found that on some devices, ZXing did not automatically adjust the white balance when the lighting conditions changed, while the native camera app did it properly (not sure if this can be fixed).
Update:
For a while I used the camera API directly. This gives more control (custom UI, etc), but I would not recommend it to anyone. I would work on 90% of devices, but every now and again a new device would be released, with a different problem.
Some of the problems I've encountered:
Handling autofocus
Handling flash
Supporting devices with a front camera, back camera or both
Each device has a different combination of screen resolution, preview resolutions (doesn't always match the screen resolution) and picture resolutions.
So in general, I'd not recommend going this route at all, unless there is no other way. After two years I dumped by custom code and switched back to the Intent-based approach. Since then I've had much less trouble. The issues I've had with the Intent-based approach in the past was probably just my own incompetence.
If you really need to go this route, I've heard it's much easier if you only support devices with Android 4.0+.
With approach 2 the issues is stability. I tried some examples, but I've managed to stop the camera from working (until a restart) on some devices and completely freeze another device. On another device the capture worked, but the preview stayed black.
Either there is a bug in the examples or there is a compatibility issue with the devices.
The example that CommonsWare gave works well. The example works when using it as-is, but here are the issues I ran into when modifying it for my use case:
Never take a second picture before the first picture has completed, in other words PictureCallback.onPictureTaken() has been called. The CommonsWare example uses the inPreview flag for this purpose.
Make sure that your SurfaceView is full-screen. If you want a smaller preview you might need to change the preview size selection logic, otherwise the preview might not fit into the SurfaceView on some devices. Some devices only support a full-screen preview size, so keeping it full-screen is the simplest solution.
To add more components to the preview screen, FrameLayout works well in my experience. I started by using a LinearLayout to add text above the preview, but that broke rule #2. When using a FrameLayout to add components on top of the preview, you don't have any issues with the preview resolution.
I also posted a minor issue relating to Camera.open() on GitHub.
"the recommended way to access the camera is to open Camera on a separate thread". Otherwise, Camera.open() can take a while and might bog down the UI thread.
"Callbacks will be invoked on the event thread open(int) was called from". That's why to achieve best performance with camera preview callbacks (e.g. to encode them in a low-latency video for live communication), I recommend to open camera in a new HandlerThread, as shown here.
I am developing an application where I have to take picture without using Media intent i-e without previewing this camera.How can I do this can anyone help me in this regard.
waiting for your reply
Altaf
You cannot take a picture without a preview. Whether it is the preview offered by the Intent or it is a preview that you create yourself with a SurfaceView when you use the Camera object, there has to be a preview.
Just use takePicture() directly on the camera object:
http://developer.android.com/reference/android/hardware/Camera.html#takePicture
I believe some of the older devices wouldn't capture correctly unless preview was setup, but I don't think that's an issue any more. And if you are looking to target devices that require preview you can just resize the preview surface to a single pixel somewhere and put another control on top of it. Still eats resources, but shouldn't be visible.
I was wondering whether it is possible to have 2 instances of the camera preview in android. What I mean is running 2 instances of the camera at the same time. If it is, how would one go about this, will there be need to implement an instance on a different thread? I have not used the camera API before, so I would appreciate it if I can have a heads up on the issue, so I don't waste time on it.
Thank you.
It is not possible to have two open connections to the camera - you have to lock the camera in order to get a preview and it can only be locked once. Indeed, if you have the camera locked, and your app crashes before you've unlocked it, then nobody can use the camera!
See http://developer.android.com/reference/android/hardware/Camera.html#open%28int%29
You must call release() when you are
done using the camera, otherwise it
will remain locked and be unavailable
to other applications.
...
RuntimeException: if connection to the
camera service fails (for example, if
the camera is in use by another
process).
That said, you can certainly register a preview callback and take the preview data from your single camera instance to use in multiple views. But be aware of the issues with the YUV format of the raw byte[] data provided by the preview callback: Getting frames from Video Image in Android (note that the preview data is raw from the camera driver and may vary from device to device)
Ignoring the big Why question, your best bet would be to make a service that interacts with the camera, and go from there.