最近遇到一个需求：画板(一张图片)上放入N个视频，N张照片，最后保存成一个完成视频。实例：一张背景图嵌入2个视频和1个图片； 看下图（gif上传到这里，就变糊了??）
实现过程：
第一步：生成主视频(背景视频)
1.背景板生成视频；
2.此视频时长要大于等于子视频的长度
2.此视频的尺寸要大于等于子视频的尺寸
图片转换CVPixelBufferRef方法在网上都能找到
- (CVPixelBufferRef)pixelBufferFromCGImage:(CGImageRef)image withSize:(CGSize)size{
int width = size.width;
int height = size.height;
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
[NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
nil];
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, width,
height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
&pxbuffer);
NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
NSParameterAssert(pxdata != NULL);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata, width,
height, 8, 4*width, rgbColorSpace,
kCGImageAlphaNoneSkipFirst);
NSParameterAssert(context);
CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
CGContextDrawImage(context, CGRectMake(0, 0, width,
height), image);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
return pxbuffer;
}
图片构造背景视频
- (void)writeImageAsMovie:(NSArray *)array toPath:(NSString*)path size:(CGSize)size completion:(HandleVideoCompletion)completion {
NSError *error = nil;
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:path]
fileType:AVFileTypeQuickTimeMovie
error:&error];
NSParameterAssert(videoWriter);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:size.width], AVVideoWidthKey,
[NSNumber numberWithInt:size.height], AVVideoHeightKey,
nil];
AVAssetWriterInput* writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings];
AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
sourcePixelBufferAttributes:nil];
NSParameterAssert(writerInput);
NSParameterAssert([videoWriter canAddInput:writerInput]);
[videoWriter addInput:writerInput];
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
CVPixelBufferRef buffer = NULL;
CMTime presentTime;
for (NSInteger i = 0; i < array.count; ++i) {
if(writerInput.readyForMoreMediaData){
if (i == 0) {
presentTime = CMTimeMake(0, 30);
} else {
presentTime = CMTimeMake(30 * i, 30);
}
buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:i] CGImage] withSize:size];
[adaptor appendPixelBuffer:buffer withPresentationTime:presentTime]; //异步添加 延时
[NSThread sleepForTimeInterval:0.05];
CMTimeShow(presentTime);
}
}
[writerInput markAsFinished];
[videoWriter finishWritingWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
if (videoWriter.status != AVAssetWriterStatusFailed && videoWriter.status == AVAssetWriterStatusCompleted) {
NSURL *videoTempURL = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@", path]];
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
[PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:videoTempURL];
} completionHandler:^(BOOL success, NSError * _Nullable error) {
if (success) {
AVAsset *asset = [AVAsset assetWithURL:videoTempURL];
completion(asset, nil);
} else {
completion(nil, error);
}
}];
} else {
completion(nil, videoWriter.error);
}
});
}];
CVPixelBufferPoolRelease(adaptor.pixelBufferPool);
}
第二步：合成视频
背景板生成了1个视频 再加上要嵌入的2个视频 那么一共就有3个视频了
最开始的思路是通过下面的方法来实现，每一个videoLayer就是一个视频 调整位置坐标，结果掉坑里了OZT
+ (instancetype)videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayers:(NSArray<CALayer *> *)videoLayers inLayer:(CALayer *)animationLayer
最后的实现方法：
for (NSInteger i = 0; i < assets.count; ++i) {
AVAsset *asset = assets[i];
AVAssetTrack *currentVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;
if (i == assets.count - 1) { //背景视频
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction
videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[i]];
[layerInstruction setTransform:currentVideoTrack.preferredTransform atTime:kCMTimeZero];
[layerInstructions addObject:layerInstruction];
continue;
}
for (NSInteger k = 0; k < pandentViews.count; ++k) { //嵌入视频
if ([pandentViews[k] isKindOfClass:[TMVideoElementView class]]) {
TMVideoElementView *videoEleView = (TMVideoElementView *)pandentViews[k];
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction
videoCompositionLayerInstructionWithAssetTrack:compositionVideoTracks[i]];
CGRect rect = videoEleView.frame; //控件在画布上的大小
CGSize videoSize = currentVideoTrack.naturalSize; //子视频大小
CGFloat scaleX = rect.size.width / videoSize.width * ratio;
CGFloat x = rect.origin.x * ratio;
CGFloat y = rect.origin.y * ratio;
CGAffineTransform t = CGAffineTransformMake(scaleX, 0, 0, scaleX, x, y);
[layerInstruction setTransform:t atTime:kCMTimeZero];
[layerInstructions addObject:layerInstruction];
}
}
}
AVMutableVideoCompositionInstruction *videoCompositionInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
videoCompositionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, backgroundAsset.duration);
videoCompositionInstruction.layerInstructions = layerInstructions;
AVMutableVideoComposition *mutableVideoComposition = [AVMutableVideoComposition videoComposition];
mutableVideoComposition.renderSize = renderSize;
mutableVideoComposition.frameDuration = CMTimeMake(1, 30);
mutableVideoComposition.instructions = @[videoCompositionInstruction];
还有视频中添加图片，就不说了，百度->添加水印。
如果有更好的方法，敬请告知。
