我正在尝试将图像拼接成预先存在的视频，以便在Mac上使用AVFoundation创建新的视频文件。
到目前为止，我已阅读Apple文档示例
ASSETWriterInput for making Video from UIImages on Iphone Issues
Mix video with static image in CALayer using AVVideoCompositionCoreAnimationTool
AVFoundation Tutorial: Adding Overlays and Animations to Videos以及其他一些SO链接
现在这些已经被证明是非常有用的，但我的问题是我没有创建静态水印或覆盖，我想在视频的各个部分之间插入图像。 到目前为止，我已经设法获取视频并创建空白部分以插入这些图像并将其导出。
我的问题是让图像在这些空白部分插入自己。我可以看到可行的唯一方法是创建一系列动画层，以便在正确的时间改变它们的不透明度，但我似乎无法让动画工作。
以下代码是我用来创建视频片段和图层动画的代码。
//https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/03_Editing.html#//apple_ref/doc/uid/TP40010188-CH8-SW7
// let's start by making our video composition
AVMutableComposition* mutableComposition = [AVMutableComposition composition];
AVMutableCompositionTrack* mutableCompositionTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableVideoComposition* mutableVideoComposition = [AVMutableVideoComposition videoCompositionWithPropertiesOfAsset:gVideoAsset];
// if the first point's frame doesn't start on 0
if (gFrames[0].startTime.value != 0)
{
DebugLog("Inserting vid at 0");
// then add the video track to the composition track with a time range from 0 to the first point's startTime
[mutableCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, gFrames[0].startTime) ofTrack:gVideoTrack atTime:kCMTimeZero error:&gError];
}
if(gError)
{
DebugLog("Error inserting original video segment");
GetError();
}
// create our parent layer and video layer
CALayer* parentLayer = [CALayer layer];
CALayer* videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, 1280, 720);
videoLayer.frame = CGRectMake(0, 0, 1280, 720);
[parentLayer addSublayer:videoLayer];
// create an offset value that should be added to each point where a new video segment should go
CMTime timeOffset = CMTimeMake(0, 600);
// loop through each additional frame
for(int i = 0; i < gFrames.size(); i++)
{
// create an animation layer and assign it's content to the CGImage of the frame
CALayer* Frame = [CALayer layer];
Frame.contents = (__bridge id)gFrames[i].frameImage;
Frame.frame = CGRectMake(0, 720, 1280, -720);
DebugLog("inserting empty time range");
// add frame point to the composition track starting at the point's start time
// insert an empty time range for the duration of the frame animation
[mutableCompositionTrack insertEmptyTimeRange:CMTimeRangeMake(CMTimeAdd(gFrames[i].startTime, timeOffset), gFrames[i].duration)];
// update the time offset by the duration
timeOffset = CMTimeAdd(timeOffset, gFrames[i].duration);
// make the layer completely transparent
Frame.opacity = 0.0f;
// create an animation for setting opacity to 0 on start
CABasicAnimation* frameAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
frameAnim.duration = 1.0f;
frameAnim.repeatCount = 0;
frameAnim.autoreverses = NO;
frameAnim.fromValue = [NSNumber numberWithFloat:0.0];
frameAnim.toValue = [NSNumber numberWithFloat:0.0];
frameAnim.beginTime = AVCoreAnimationBeginTimeAtZero;
frameAnim.speed = 1.0f;
[Frame addAnimation:frameAnim forKey:@"animateOpacity"];
// create an animation for setting opacity to 1
frameAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
frameAnim.duration = 1.0f;
frameAnim.repeatCount = 0;
frameAnim.autoreverses = NO;
frameAnim.fromValue = [NSNumber numberWithFloat:1.0];
frameAnim.toValue = [NSNumber numberWithFloat:1.0];
frameAnim.beginTime = AVCoreAnimationBeginTimeAtZero + CMTimeGetSeconds(gFrames[i].startTime);
frameAnim.speed = 1.0f;
[Frame addAnimation:frameAnim forKey:@"animateOpacity"];
// create an animation for setting opacity to 0
frameAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
frameAnim.duration = 1.0f;
frameAnim.repeatCount = 0;
frameAnim.autoreverses = NO;
frameAnim.fromValue = [NSNumber numberWithFloat:0.0];
frameAnim.toValue = [NSNumber numberWithFloat:0.0];
frameAnim.beginTime = AVCoreAnimationBeginTimeAtZero + CMTimeGetSeconds(gFrames[i].endTime);
frameAnim.speed = 1.0f;
[Frame addAnimation:frameAnim forKey:@"animateOpacity"];
// add the frame layer to our parent layer
[parentLayer addSublayer:Frame];
gError = nil;
// if there's another point after this one
if( i < gFrames.size()-1)
{
// add our video file to the composition with a range of this point's end and the next point's start
[mutableCompositionTrack insertTimeRange:CMTimeRangeMake(gFrames[i].startTime,
CMTimeMake(gFrames[i+1].startTime.value - gFrames[i].startTime.value, 600))
ofTrack:gVideoTrack
atTime:CMTimeAdd(gFrames[i].startTime, timeOffset) error:&gError];
}
// else just add our video file with a range of this points end point and the videos duration
else
{
[mutableCompositionTrack insertTimeRange:CMTimeRangeMake(gFrames[i].startTime, CMTimeSubtract(gVideoAsset.duration, gFrames[i].startTime)) ofTrack:gVideoTrack atTime:CMTimeAdd(gFrames[i].startTime, timeOffset) error:&gError];
}
if(gError)
{
char errorMsg[256];
sprintf(errorMsg, "Error inserting original video segment at: %d", i);
DebugLog(errorMsg);
GetError();
}
}
现在在该片段中，Frame的不透明度设置为0.0f，但是当我将其设置为1.0f时，只需将这些帧中的最后一个放置在视频的整个持续时间之上。
之后使用AVAssetExportSession导出视频，如下所示
mutableVideoComposition.animationTool = [AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
// create a layer instruction for our newly created animation tool
AVMutableVideoCompositionLayerInstruction *layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:gVideoTrack];
AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
[instruction setTimeRange:CMTimeRangeMake(kCMTimeZero, [mutableComposition duration])];
[layerInstruction setOpacity:1.0f atTime:kCMTimeZero];
[layerInstruction setOpacity:0.0f atTime:mutableComposition.duration];
instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
// set the instructions on our videoComposition
mutableVideoComposition.instructions = [NSArray arrayWithObject:instruction];
// export final composition to a video file
// convert the videopath into a url for our AVAssetWriter to create a file at
NSString* vidPath = CreateNSString(outputVideoPath);
NSURL* vidURL = [NSURL fileURLWithPath:vidPath];
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mutableComposition presetName:AVAssetExportPreset1280x720];
exporter.outputFileType = AVFileTypeMPEG4;
exporter.outputURL = vidURL;
exporter.videoComposition = mutableVideoComposition;
exporter.timeRange = CMTimeRangeMake(kCMTimeZero, mutableComposition.duration);
// 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(), ^{
if (exporter.status == AVAssetExportSessionStatusCompleted)
{
DebugLog("!!!file created!!!");
_Close();
}
else if(exporter.status == AVAssetExportSessionStatusFailed)
{
DebugLog("failed damn");
DebugLog(cStringCopy([[[exporter error] localizedDescription] UTF8String]));
DebugLog(cStringCopy([[[exporter error] description] UTF8String]));
_Close();
}
else
{
DebugLog("NoIdea");
_Close();
}
});
}];
}
我觉得动画没有开始，但我不知道。我是否正确地将图像数据拼接成这样的视频？
非常感谢任何协助。
答案 0 :(得分：3)
我用另一种方式解决了我的问题。动画路线不起作用，所以我的解决方案是将所有可插入的图像编译成临时视频文件，并使用该视频将图像插入到我的最终输出视频中。
从我最初发布的第一个链接ASSETWriterInput for making Video from UIImages on Iphone Issues开始，我创建了以下函数来创建我的临时视频
void CreateFrameImageVideo(NSString* path)
{
NSLog(@"Creating writer at path %@", path);
NSError *error = nil;
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
[NSURL fileURLWithPath:path] fileType:AVFileTypeMPEG4
error:&error];
NSLog(@"Creating video codec settings");
NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:gVideoTrack.estimatedDataRate/*128000*/], AVVideoAverageBitRateKey,
[NSNumber numberWithInt:gVideoTrack.nominalFrameRate],AVVideoMaxKeyFrameIntervalKey,
AVVideoProfileLevelH264MainAutoLevel, AVVideoProfileLevelKey,
nil];
NSLog(@"Creating video settings");
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
codecSettings,AVVideoCompressionPropertiesKey,
[NSNumber numberWithInt:1280], AVVideoWidthKey,
[NSNumber numberWithInt:720], AVVideoHeightKey,
nil];
NSLog(@"Creating writter input");
AVAssetWriterInput* writerInput = [[AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings] retain];
NSLog(@"Creating adaptor");
AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
sourcePixelBufferAttributes:nil];
[videoWriter addInput:writerInput];
NSLog(@"Starting session");
//Start a session:
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];
CMTime timeOffset = kCMTimeZero;//CMTimeMake(0, 600);
NSLog(@"Video Width %d, Height: %d, writing frame video to file", gWidth, gHeight);
CVPixelBufferRef buffer;
for(int i = 0; i< gAnalysisFrames.size(); i++)
{
while (adaptor.assetWriterInput.readyForMoreMediaData == FALSE) {
NSLog(@"Waiting inside a loop");
NSDate *maxDate = [NSDate dateWithTimeIntervalSinceNow:0.1];
[[NSRunLoop currentRunLoop] runUntilDate:maxDate];
}
//Write samples:
buffer = pixelBufferFromCGImage(gAnalysisFrames[i].frameImage, gWidth, gHeight);
[adaptor appendPixelBuffer:buffer withPresentationTime:timeOffset];
timeOffset = CMTimeAdd(timeOffset, gAnalysisFrames[i].duration);
}
while (adaptor.assetWriterInput.readyForMoreMediaData == FALSE) {
NSLog(@"Waiting outside a loop");
NSDate *maxDate = [NSDate dateWithTimeIntervalSinceNow:0.1];
[[NSRunLoop currentRunLoop] runUntilDate:maxDate];
}
buffer = pixelBufferFromCGImage(gAnalysisFrames[gAnalysisFrames.size()-1].frameImage, gWidth, gHeight);
[adaptor appendPixelBuffer:buffer withPresentationTime:timeOffset];
NSLog(@"Finishing session");
//Finish the session:
[writerInput markAsFinished];
[videoWriter endSessionAtSourceTime:timeOffset];
BOOL successfulWrite = [videoWriter finishWriting];
// if we failed to write the video
if(!successfulWrite)
{
NSLog(@"Session failed with error: %@", [[videoWriter error] description]);
// delete the temporary file created
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:path]) {
NSError *error;
if ([fileManager removeItemAtPath:path error:&error] == NO) {
NSLog(@"removeItemAtPath %@ error:%@", path, error);
}
}
}
else
{
NSLog(@"Session complete");
}
[writerInput release];
}
创建视频后，将其作为AVAsset加载，然后提取它的轨道，然后通过替换以下行（来自原始帖子中的第一个代码块）插入视频
[mutableCompositionTrack insertEmptyTimeRange:CMTimeRangeMake(CMTimeAdd(gFrames[i].startTime, timeOffset), gFrames[i].duration)];
使用：
[mutableCompositionTrack insertTimeRange:CMTimeRangeMake(timeOffset,gAnalysisFrames[i].duration)
ofTrack:gFramesTrack
atTime:CMTimeAdd(gAnalysisFrames[i].startTime, timeOffset) error:&gError];
其中gFramesTrack是从临时帧视频创建的AVAssetTrack。
所有与CALayer和CABasicAnimation对象相关的代码都已删除，因为它不起作用。
不是最优雅的解决方案，我不会想到，但至少可以起作用。我希望有人觉得这很有用。
此代码也适用于iOS设备（使用iPad 3测试）
旁注：第一篇文章中的DebugLog函数只是对打印日志消息的函数的回调，如果需要，可以用NSLog（）调用替换它们。