at a bit of a loss here.
Basically, I need to create a frame server that will give my app an image of each frame contained in the video at said video's frame rate. I need to do this while also playing its audio.
I'll be using these frames as a texture source for certain geometries on an SceneKit
Have never used AVFoundation, any pointers, tutorials or suggestions are welcomed
That's a very general question.
Since you've never used AVFoundation, the AVFoundation Programming Guide should be your first stop.
In particular, the Still and Video Media Capture section shows how to set a delegate for the capture process.
Related
I'm currently working on app that records video of user, binds particle emitters to hands landmarks on preview. In result effects are shown on camera preview, but they aren't captured on video.
I saw a great tutorial on AVVideoCompositionCoreAnimationTool https://www.raywenderlich.com/6236502-avfoundation-tutorial-adding-overlays-and-animations-to-videos, but that way it only is possible to rendere animations on already recoded video.
I wonder if there is any chance to use AVVideoCompositionCoreAnimationTool for recording video form camera and animations in real time. Or if you know other method to do it, without diving deep in metal and so on.
Thanks in advance!
I am trying to integrate a functionality where i have to capture multiple frames let say 3 frames in a second and at last combines all captured frames to form a video and upload that video on server.
You can refer the functionality same as happens in boomerang, i have searched a lot about the most effective way to do the same but didn't found anything helpful.
Any guidance is appreciated.
Video From Image Array
For combining your image array to video please make use of widely accepted answer here.
By using AVAssetWriter and CVPixelBufferRef .
To Make Video in reverse order
This can be done effectively Using the AVFoundation library.
Use AVAssetReader to read the video and Use AVAssetWriter to write the video in reverse order.
Refer the tutorial Reverse Video AVFoundation
I am working on an application where video and time/GPS/accelerometer data is simultaneously recorded to separate files.
I can play the video and have my overlay appear perfectly in realtime, but I cannot simply export this.
I am wanting to post-process the video and overlay the time,coordinates and on the video.
There are other shapes that will be overlayed which change size/position on each frame.
I have tried using AVMutableComposition and adding CALayers with limited results-
This works to an extent but I cannot synchronise the timestamp with the video. I could use a CAKeyframeAnimation with values+keyTimes, but the amount of values I need to work with is excessive.
My current approach is to render a separate video consisting of CGImages created using the data. This works well but I will need to use a ChromaKey to have transparency in the overlay. I have read that there will likely be quality issues after doing this.
Is there a simpler approach that I should be looking at?
I understand that render speed will not be fantastic, however I do not wish to require a separate 'PC' application to render the video.
Use AVAssetReader for recorded video. Get the CMSampleBufferRef, get it timestamp, draw time on sample buffer, write buffer to AVAssetWriterInputPixelBufferAdaptor. Similar approach for video being recorded.
Use the AVVideoCompositing protocol https://developer.apple.com/library/mac/documentation/AVFoundation/Reference/AVVideoCompositing_Protocol/index.html
This will allow you to get frame by frame call backs with the pixel buffers to do what you want.
With this protocol you will be able to take one frame and overlay whoever you would like. Take a look at This sample - https://developer.apple.com/library/ios/samplecode/AVCustomEdit/Introduction/Intro.html to see how to handle frame by frame modifications. If you take advantage of the AVVideoCompositing protocol you can set a custom video compositor and a video composition on your AVPlayerItem and AVExportSession to render/export what you want.
I'm looking for a tips to develop an application for iPhone/iPad that will be able to process video (let's consider only local files stored on the device for simplicity) and play it in real-time. For example you can choose any movie and choose "Old movie" filter and want it like on old lamp TV.
In order to make this idea real i need to implement two key features:
1) Grab frames and audio stream from a movie file and get access to separate frames (I'm interested in raw pixel buffer in BGRA or at least YUV color space).
2) Display processed frames somehow. I know it's possible to render processed frame to OpenGL texture, but i would like to have more powerful component with playback controls. Is there any class of media player that supports playing custom image and audio buffers?
The processing function is done and it's fast (less than duration on one frame).
I'm not asking for ready solution, but any tips are welcome!
Answer
Frame grabbing.
It seems the only way to grab video and audio frames is to use AVAssetReader class. Although it's not recommended to use for real-time grabbing it does the job. In my tests on iPad2 grabbing single frame needs about 7-8 ms. Seeking across the video is a tricky. Maybe someone can point to more efficient solution?
Video playback. I've done this with custom view and GLES to render a rectangle texture with a video frame inside of it. As far as i know it's the fastest way to draw bitmaps.
Problems
Need to manually play a sound samples
AVAssetReader grabbing should be synchronized with a movie frame rate. Otherwise movie will go too fast or too slow.
AVAssetReader allows only continuous frame access. You can't seek forward and backward. Only proposed solution is to delete old reader and create a new with trimmed time range.
This is how you would load a video from the camera roll..
This is a way to start processing video. Brad Larson did a great job..
How to grab video frames..
You can use AVPlayer+ AVPlayerItem, it provide you a chance to apply a filter on the display image.
I wonder if it's possible in iOS 4 or 5 to save into a single video file not just a stream from camera, but a stream from camera WITH custom view(s) overlaid. Custom view will contain few labels with transparent background. Those labels will show additional info: current time and GPS coordinates. And every video player must be able to playback that additional info.
I think you can use AVCaptureVideoDataOutput to process each frame and use AVAssetWriter to record the processed frame.You can refer to this answer
https://stackoverflow.com/a/4944594/379941 .
And you can process CVImageBufferRef then use AVAssetWriterPixelBufferAdaptor's appendPixelBuffer:withPresentationTime: method to export.
And I strongly suggest using OpenCV to process frame. this is a nice tutorial http://aptogo.co.uk/2011/09/opencv-framework-for-ios/. OpenCV library is very great.