iOS AVFoundation - 显示视频和导出的时间显示 [英] iOS AVFoundation - Show a time display over a video and export

问题描述

我想在视频上显示一个显示叠加层并导出包含此显示的视频。我看了AVFoundation框架，AVCompositions，AVAssets等，但我仍然没有想到实现这一目标。有一个名为AVSynchronizedLayer的类可以让你动画与视频同步的动画，但是我不想动画，我想要将时间显示叠加到视频的每一帧中。有什么建议吗？

I want to show a display overlay over a video and export that video including this display. I had a look into the AVFoundation Framework, AVCompositions, AVAssets etc. but I still do not have an idea to achieve this. There is a class called AVSynchronizedLayer which lets you animate things synchrounous to the video, but I do not want to animate, I jsut want to overlay the time display into every single frame of the video. Any advice?

问候

推荐答案

这样的事......

Something like this...

（注意：从一个更大的项目中淘汰，所以我可能偶然包含了一些不必要的部分）。

(NB: culled from a much larger project, so I may have included some unnecessary pieces by accident).

你需要抓住时钟/动画的CALayer，并将其设置为var myClockLayer（使用andimation工具使用1/3）。

You'll need to grab the CALayer of your clock / animation, and set it to the var myClockLayer (used 1/3 of the way down by the andimation tool).

这也假设您的传入视频只有两个音轨 - 音频和视频。如果您有更多，则需要更仔细地设置asTrackID：2中的曲目ID。

This also assumes your incoming video has just two tracks - audio and video. If you have more, you'll need to set the track id in "asTrackID:2" more carefully.

AVURLAsset* url = [AVURLAsset URLAssetWithURL:incomingVideo options:nil];
AVMutableComposition *videoComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [videoComposition  addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVAssetTrack *clipVideoTrack = [[url tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [url duration])  ofTrack:clipVideoTrack atTime:kCMTimeZero error:&error];

AVMutableVideoComposition* videoComposition = [[AVMutableVideoComposition videoComposition]retain];
videoComposition.renderSize = CGSizeMake(320, 240);
videoComposition.frameDuration = CMTimeMake(1, 30);
videoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithAdditionalLayer:myClockLayer asTrackID:2];

AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(60, 30) );

AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:clipVideoTrack];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];

videoComposition.instructions = [NSArray arrayWithObject: instruction];

exporter = [[AVAssetExportSession alloc] initWithAsset:saveComposition presetName:AVAssetExportPresetHighestQuality] ;
exporter.videoComposition = videoComposition;
exporter.outputURL=url3;
exporter.outputFileType=AVFileTypeQuickTimeMovie;

[exporter exportAsynchronouslyWithCompletionHandler:^(void){}];

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