【发布时间】：2015-09-21 01:41:48
【问题描述】：
我想要的：在 AVVideoCompositionTrack 的时间 0:00 插入多个不透明的视频层。
我仔细阅读了官方的 AVFoundation 文档以及关于这个主题的许多 WWDC 讨论。但我不明白为什么结果不遵循 API 语句。
我可以在播放过程中使用 2 AVPlayerLayer 实现叠加效果。这也可能意味着我可以在导出过程中使用 AVVideoCompositionCoreAnimationTool 来实现类似的东西。 但我倾向于将 CALayer 留给字幕/图像叠加或动画。
我对任何插入 AVAsset 的尝试：
- (void)addVideo:(AVAsset *)asset_in withOpacity:(float)opacity
{
// This is demo for composition of opaque videos. So we all insert video at time - 0:00
[_videoCompositionTrack insertTimeRange:CMTimeRangeMake( kCMTimeZero, asset_in.duration )
ofTrack:[ [asset_in tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0 ]
atTime:kCMTimeZero error:nil ];
AVMutableVideoCompositionInstruction *mutableVideoCompositionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
AVAssetTrack *assettrack_in = [ [asset_in tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0 ];
mutableVideoCompositionInstruction.timeRange = CMTimeRangeMake( kCMTimeZero, assettrack_in.timeRange.duration );
AVMutableVideoCompositionLayerInstruction *videoCompositionLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:_videoCompositionTrack];
[videoCompositionLayerInstruction setTransform:assettrack_in.preferredTransform atTime:kCMTimeZero];
[videoCompositionLayerInstruction setOpacity:opacity atTime:kCMTimeZero];
mutableVideoCompositionInstruction.layerInstructions = @[videoCompositionLayerInstruction];
[_arrayVideoCompositionInstructions addObject:mutableVideoCompositionInstruction];
}
请注意 insertTimeRange 有 atTime:kCMTimeZero 作为参数。所以我希望它们会放在视频合成的开头。
我尝试导出的内容：
- (IBAction)ExportAndPlay:(id)sender
{
_mutableVideoComposition.instructions = [_arrayVideoCompositionInstructions copy];
// Create a static date formatter so we only have to initialize it once.
static NSDateFormatter *kDateFormatter;
if (!kDateFormatter) {
kDateFormatter = [[NSDateFormatter alloc] init];
kDateFormatter.dateStyle = NSDateFormatterMediumStyle;
kDateFormatter.timeStyle = NSDateFormatterShortStyle;
}
// Create the export session with the composition and set the preset to the highest quality.
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:_mutableComposition presetName:AVAssetExportPresetHighestQuality];
// Set the desired output URL for the file created by the export process.
exporter.outputURL = [[[[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:@YES error:nil] URLByAppendingPathComponent:[kDateFormatter stringFromDate:[NSDate date]]] URLByAppendingPathExtension:CFBridgingRelease(UTTypeCopyPreferredTagWithClass((CFStringRef)AVFileTypeQuickTimeMovie, kUTTagClassFilenameExtension))];
// Set the output file type to be a QuickTime movie.
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.videoComposition = _mutableVideoComposition;
_mutableVideoComposition.instructions = [_arrayVideoCompositionInstructions copy];
// Asynchronously export the composition to a video file and save this file to the camera roll once export completes.
[exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
switch ([exporter status]) {
case AVAssetExportSessionStatusFailed:
{
NSLog(@"Export failed: %@ %@", [[exporter error] localizedDescription],[[exporter error]debugDescription]);
}
case AVAssetExportSessionStatusCancelled:
{
NSLog(@"Export canceled");
break;
}
case AVAssetExportSessionStatusCompleted:
{
NSLog(@"Export complete!");
NSLog( @"Export URL = %@", [exporter.outputURL absoluteString] );
[self altPlayWithUrl:exporter.outputURL];
}
default:
{
NSLog(@"default");
}
}
} );
}];
}
结果：如果我选择 2 个视频剪辑，它会导出一个视频，并在第一个视频之后附加第二个视频。
这与我从 :AVMutableCompositionTrack 读到的内容不同
有人可以为这只无助的羔羊提供一些启示吗？
编辑：是否缺少任何细节，以至于没有人可以帮我一把？如果是这样，请留下评论，以便我可以弥补。
【问题讨论】：
标签： ios objective-c avfoundation