I'm using the two OpenCV functions mentioned above to retrieve frames from my webcam. No additional properties are set, just running with default parameters.
Here cvQueryFrame() always returns frames in size 640x480, independent from the native resolution of the camera. But how can I get full size frames when I don't know the exact resolution of it and therefore can't set width and height property? Is there a way to reset these 640x480 settings? Or is there a possibility to query the device for the maximum resolution it supports?
Thanks!
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On my iPad with a digital zoom of 5x, the reported captureDevice.maxAvailableVideoZoomFactor for the camera device is 153.
Shouldn't it be 5? Am I using the right property to get the max zoom factor?
I found this from link:
On single-camera devices, this value is always equal to the device format’s videoMaxZoomFactor value. On a dual-camera device, the allowed range of video zoom factors can change if the device is delivering depth data to one or more capture outputs.
So if your iPad has dual/triple cameras and you are using buildInDualCamera, etc. It can return a bigger max zoom level.
I' trying to capture video by AVAssetWriter and AVCaptureOutput
You can find sample project here.
The video should be in portrait mode with any resolution. The main problem that it should be in portrait mode.
I'm trying to set different setting, but in the end, video is rotated and scaled to size (1920x1080) on iPhone SE.
Is it possible to control this resolution? Or at least orientation?
Video resolution is determined by the AVCaptureSession sessionPreset. You're setting that to medium, so you're getting the resolution that comes with that. If you want a different resolution, pass a different session preset, or use AVCaptureDevice to set a specific capture format. (For a good overview of capture session presets vs device formats, go back to this WWDC13 video.)
Per this Apple Developer Q&A, you need to set an orientation on the capture connection after you start the capture session in order to get "physically" rotated frame buffers (at a capture performance cost), or set the transform property on your asset writer (so that buffers are recorded in the sensor's native orientation, but clients display it in your intended orientation).
I'd like to capture high resolution still images using AVCaptureSession. Therefore AVCaptureSession preset is set to Photo.
This is working well so far. On an iPhone 4 the final still image resolution is at its maximum of 2448x3264 pixels and the preview (video) resolution is 852x640 pixels.
Now, because the preview frames are analyzed to detect objects in the scene, I'd like to lower their resolution. How can this be done?
I've tried to set AVVideoSettings with a lower width/height to AVCaptureVideoDataOutput, but this leads to the following error message:
AVCaptureVideoDataOutput setVideoSettings:] - videoSettings dictionary contains one or more unsupported (ignored) keys: (AVVideoHeightKey, AVVideoWidthKey
So it seems this is not the right approach to configure the size of the preview frames received by AVCaptureVideoDataOutput / AVCaptureVideoDataOutputSampleBufferDelegate. Do you have any ideas how the resolution of the preview frames can be configured?
Any advise is welcome,
Thank you.
If you want to specify the settings manually, you need to set activeFormat on the AVCaptureDevice. This will be implicitly set the session preset to AVCaptureSessionPresetInputPriority.
The activeFormat takes a AVCaptureDeviceFormat but you can only take one from the list of AVCaptureDevice.formats. You'll need to go through the list and find one that fits your needs. Specifically, check that highResolutionStillImageDimensions is high enough for desired still capture and formatDescription (which needs to be inspected with CMFormatDescription* functions, e.g., CMVideoFormatDescriptionGetDimensions) matches your desired preview settings.
Just for the records: I ended up configuring AVCaptureSession in preset Low while aiming the camera. As soon as the shutter is triggered, the app switches to preset Photo, performs a focus run and takes the picture. This way it takes between 1 and 2.5 seconds to take a picture, which isn't that great, but it's at least a workaround.
To lower the size of the output of AVCaptureVideoDataOutput you can set the bitrate to be lower thus producing a small sample size.
commonly used keys for AVCaptureVideoDataOutput are:
AVVideoAverageBitRateKey
AVVideoProfileLevelKey
AVVideoExpectedSourceFrameRateKey
AVVideoMaxKeyFrameIntervalKey
For example:
private static let videoCompressionOptionsMedium = [AVVideoAverageBitRateKey : 1750000,
AVVideoProfileLevelKey : AVVideoProfileLevelH264BaselineAutoLevel,
AVVideoExpectedSourceFrameRateKey : Int(30),
AVVideoMaxKeyFrameIntervalKey : Int(30)]
I'm using AVCaptureSession to capture and record a video.
I need to record the video at a 4:3 ratio, and with a good resolution.
Is there a way to specify a custom resolution when capturing using AVCaptureSession?
I tried using the native presets but the problem is that I need to capture at a 4:3 ratio, and almost all of the presets are 16:9. and the ones that are 4:3 has very low resolution.
I can't fide any other way to change the preset to a custom one, what if I need to capture a 4:3 video with better resolution? Any ideas?
AVCaptureSession presets cover only a small subset of the capabilities of a device camera (the ones most apps want quick, easy access to). For more fine-grained control — such as to select a capture resolution not provided by a session preset — you need to use capture formats instead.
Look at the capture device's formats property, an array of AVCaptureDeviceFormat objects. Enumerate through that array until you find one whose dimensions are what you want. To get the dimensions, look at the format's underlying CMFormatDescription:
let fdesc = format.formatDescription
let dims = CMVideoFormatDescriptionGetDimensions(fdesc)
NSLog("%d x %d", dims.width, dims.height)
Once you've found the format you want, lock the device for configuration and set its activeFormat:
if try device.lockForConfiguration() {
device.activeFormat = myChosenFormat
// set up other things like activeVideoMinFrameDuration if you want
device.unlockForConfiguration()
}
You can find out more about configuring a capture session via AVCaptureDeviceFormat in Apple's programming guide and the WWDC2013 session that introduced device formats back in iOS 7.0. (Most of what you'll find about this topic is aimed at slow-motion video, taking high-res stills during video, and other things that you can't do with session presets, but those aren't the only things you can do with capture formats.)
Just record at the given aspect ratio and use an AVMutableComposition to crop the output video to the required aspect ratio: If you adjust the preview layer to mask to 4:3 this will appear seamless to the user.
I have this camera App where I'd like to get the max resolution image in the didOutputSampleBuffer callback. Right now all the frames I receive in the callback are 852 x 640 (I am using an iPhone 4 for testing). Only when I request for a still image capture (via captureStillImageAsynchronouslyFromConnection) do I get one - and only one - frame corresponding to the actual image captured in the highest resolution of the device - 2592x1936.
Is it possible to set things up so that I constantly receive frames of resolution - 2592x1936 in didOutputSampleBuffer? Then I would like to save some of these frames as images in the callback without having to go through captureStillImageAsynchronouslyFromConnection to capture an image.
Video output can't support the full resolution that you see when capturing still images. Look at the table given in Use Capture Outputs to Get Output from a Session for a list of supported resolutions.
If you want to change the resolution set the appropriate setting on your camera session like so:
cameraSession.sessionPreset = AVCaptureSessionPresetHigh;
Note that AVCaptureSessionPresetPhoto isn't possible with video capture.