Cropping videos in iOS

问题

We can crop images. Can we crop videos?

回答1:

Since video is a collection of pictures you can crop all frames from video and after create new video. AVFoundation guide describe some tasks: Putting it all Together: Capturing Video Frames as UIImage Objects After this you crops images and write video

You can use an asset writer to produce a QuickTime movie file or an MPEG-4 file from media such as sample buffers or still images.

See for more details AV Foundation Framework

回答2:

[[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:inputURL options:nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetLowQuality];
exportSession.outputURL = outputURL;
exportSession.shouldOptimizeForNetworkUse = YES;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;

CMTime start = CMTimeMakeWithSeconds(1.0, 600);
CMTime duration = CMTimeMakeWithSeconds(120.0, 600);
CMTimeRange range = CMTimeRangeMake(start, duration);
exportSession.timeRange = range;

[exportSession exportAsynchronouslyWithCompletionHandler:^(void){
               handler(exportSession);
               [exportSession release];}];

Here we get a video of first 2 mins.

回答3:

You should be able to do this using AVAssetExportSession, AVVideoComposition, and AVVideoCompositionCoreAnimationTool (and just set up a CALayer hierarchy with the positioning you want). I'm not sure if this is the most efficient way, though.

回答4:

it's not as simple as images

but it could be as easy as the correct specification of the video but there is not enough information.

in the decoding settings, you can manipulate video pixels by geometry, ie, anamorphic, squeezed, stretched and also player/browser settings, the image window or player window, you can specify a small player window and a magnification level. if you allow or disallow zoom/magnification, you'll force an offscreeen draw or black bars.

i would encode to the correct size and platform for best quality, these kinds of fixes are 'kludges' but they work in a pinch. i would grab the quicktime sdk and poke around.

来源：https://stackoverflow.com/questions/6212889/cropping-videos-in-ios