最近需要做一个功能，给视频添加字幕，关键还是OC的代码，愁啊。
这种没做过的东西就只能面对搜索引擎编程了。
各种搜索和尝试，最后弄了两天给弄出来了，唯一不足的就是字幕的清晰度不够，也暂时不知道是不是视频合成质量的问题。
简单说一下整个流程的思路及关键点：
1. 创建AVMutableComposition 和 AVMutableCompositionTrack
AVMutableComposition *mix = [AVMutableComposition composition];
// 视频轨道
AVMutableCompositionTrack *videoTrack = [mix addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
//音频轨道
AVMutableCompositionTrack *audioTrack = [mix addMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCMPersistentTrackID_Invalid];
2. 把资源放进Track
[videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:videoTrack.asset.duration error:nil];
[AudioTrack insertTimeRange:CMTimeRangeFromTimeToTime(kCMTimeZero, videoTrack.asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
3.创建导出
self.exporter = [[AVAssetExportSession alloc] initWithAsset:mix presetName:AVAssetExportPreset3840x2160];
4. AVMutableVideoComposition 和 AVMutableVideoCompositionInstruction
//AVMutableVideoComposition：管理所有视频轨道，可以决定最终视频的尺寸，裁剪需要在这里进行
AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];
// AVMutableVideoCompositionInstruction 视频轨道中的一个视频，可以缩放、旋转等
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
5.添加字幕或水印
// videoLayer是视频layer,parentLayer是最主要的，videoLayer和字幕，贴纸的layer都要加在该layer上
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
...
[parentLayer addSublayer: 字幕layer];
因为主要就是要添加字幕，所以这里的逻辑我会重点说一下。
字幕其实就是放在视频layer层上的文字（label），但是它们是隐藏的，并且在指定时间出现又在指定时间消失。也就是说要给这个layer加上一个动画组，第一个动画是将透明度变为1，第二个动画将透明度变为0
将字幕文件解析后，将动画组的beginTime设为开始时间，duration设为持续时间，同时将消失动画的beginTime设为持续时间，duration设为0.1
6. AVVideoCompositionCoreAnimationTool 以及 exporter的赋值
mainCompositionInst.animationTool = [AVVideoCompositionCoreAnimationTool
videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
/// 设置字幕 layer层
self.exporter.videoComposition = mainCompositionInst;
7.导出
[self.exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
});
}];
感谢愛我你就抱抱我——ios 通过AVFoundation给视频添加字幕的这篇文章，不然我对添加字幕毫无头绪。虽然文章里面没有完整的字幕动画代码...
完整代码如下，这里面的代码是有实际业务需求的代码，所以会有一些变动。
另外添加字幕label的时候我碰到了一个特别奇怪的问题。如果只添加一个label.layer，没有问题，如果放入for循环中循环添加，一个都加不上去。尝试半天不知道为什么，最后灵机一动，加了一句添加label到view上，结果就可以了。
然后由于label添加的字幕清晰度不行，暂时也不知道是视频合成的原因还是说自己分辨率造成的。所以换成了CATextLayer，比label清晰了那么一丢丢。但是发现我设置了textLayer.contentsScale = [UIScreen mainScreen].scale;反而更不清晰了，所以就屏蔽了这个contentsScale
/**
@param videos 需要被合成的音频文件
@param audios 需要被合成的视频文件
*/
- (void)compositionVideos:(NSArray <NSURL *>*)videos audios:(NSArray <NSURL *>*)audios
{
[SVProgressHUD setDefaultMaskType:(SVProgressHUDMaskTypeClear)];
[SVProgressHUD showWithStatus:@"正在合成..."];
NSMutableArray *videosAsset = [NSMutableArray arrayWithCapacity:0];
NSMutableArray *audiosAsset = [NSMutableArray arrayWithCapacity:0];
for (NSURL *videoPath in videos) {
AVAsset *asset = [AVAsset assetWithURL:videoPath];
NSLog(@"%@",asset);
[videosAsset insertObject:asset atIndex:videosAsset.count];
}
for (NSURL *audioPath in audios) {
AVAsset *asset = [AVAsset assetWithURL:audioPath];
[audiosAsset insertObject:asset atIndex:audiosAsset.count];
}
// 1 - 创建 AVMutableComposition 对象. 对象将保存AVMutableCompositionTrack实例.
AVMutableComposition *mix = [AVMutableComposition composition];
// 2 - 视频轨道
AVMutableCompositionTrack *videoTrack = [mix addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[videosAsset enumerateObjectsUsingBlock:^(AVAsset *asset, NSUInteger idx, BOOL *stop) {
[videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:videoTrack.asset.duration error:nil];
}];
NSMutableArray *audioTrackes = [NSMutableArray arrayWithCapacity:0];
[audiosAsset enumerateObjectsUsingBlock:^(AVAsset *asset, NSUInteger idx, BOOL *stop) {
AVMutableCompositionTrack *AudioTrack = [mix addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:(int32_t)idx];
[AudioTrack insertTimeRange:CMTimeRangeFromTimeToTime(kCMTimeZero, videoTrack.asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];
[audioTrackes addObject:AudioTrack];
}];
// 4 - 获取路径
NSURL *url = [EditAudioVideo exporterVideoPath];
// 5 - 创建导出
self.exporter = [[AVAssetExportSession alloc] initWithAsset:mix presetName:AVAssetExportPreset3840x2160];
//修改背景音乐的音量start
AVMutableAudioMix *videoAudioMixTools = [AVMutableAudioMix audioMix];
//获取音频轨道
NSMutableArray *inputParameters = [NSMutableArray arrayWithCapacity:0];
[audiosAsset enumerateObjectsUsingBlock:^(AVAsset *asset, NSUInteger idx, BOOL *stop) {
AVMutableAudioMixInputParameters *audioParameters = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:audioTrackes[idx]];
[audioParameters setVolumeRampFromStartVolume:1.0 toEndVolume:1.0 timeRange:CMTimeRangeMake(kCMTimeZero, CMTimeAdd(kCMTimeZero, asset.duration))];
[audioParameters setTrackID:(int32_t)idx];
[inputParameters addObject:audioParameters];
}];
videoAudioMixTools.inputParameters = inputParameters;
//3.1 AVMutableVideoCompositionInstruction 视频轨道中的一个视频，可以缩放、旋转等
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoTrack.asset.duration);
/// 3.2 AVMutableVideoCompositionLayerInstruction 一个视频轨道，包含了这个轨道上的所有视频素材
/// 必须依靠它
AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
//1 创建AVAsset实例 AVAsset包含了video的所有信息 self.videoUrl输入视频的路径
AVAssetTrack *videoAssetTrack = [[videoTrack.asset tracksWithMediaType:AVMediaTypeVideo] firstObject];
UIImageOrientation videoAssetOrientation_ = UIImageOrientationUp;
BOOL isVideoAssetPortrait_ = NO;
CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
videoAssetOrientation_ = UIImageOrientationRight;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
videoAssetOrientation_ = UIImageOrientationLeft;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {
videoAssetOrientation_ = UIImageOrientationUp;
}
if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {
videoAssetOrientation_ = UIImageOrientationDown;
}
[videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
[videolayerInstruction setOpacity:0.0 atTime:videoTrack.asset.duration];
mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];
//AVMutableVideoComposition：管理所有视频轨道，可以决定最终视频的尺寸，裁剪需要在这里进行
AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];
CGSize naturalSize;
if(isVideoAssetPortrait_){
naturalSize = CGSizeMake(videoTrack.naturalSize.height, videoTrack.naturalSize.width);
} else {
naturalSize = videoTrack.naturalSize;
}
/// 设置高宽
float renderWidth, renderHeight;
renderWidth = naturalSize.width;
renderHeight = naturalSize.height;
mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake(1, 30);
/// 加水印 加字幕
// videoLayer是视频layer,parentLayer是最主要的，videoLayer和字幕，贴纸的layer都要加在该layer上
CALayer *parentLayer = [CALayer layer];
CALayer *videoLayer = [CALayer layer];
parentLayer.frame = CGRectMake(0, 0, renderWidth, renderHeight);
videoLayer.frame = CGRectMake(0, 0, renderWidth, renderHeight);
[parentLayer addSublayer:videoLayer];
for (IVYSubTitleManager *obj in [IVYSubTitleManager manager].subTitles) {
// UILabel * titleLabel = [[UILabel alloc]initWithFrame: CGRectMake(8, 8, kScreenW - 16, 38)];
// titleLabel.attributedText = [[IVYSubTitleManager manager] getSRTSubtitleWithCurrentObj:obj];
// titleLabel.minimumScaleFactor = 9/14;
// titleLabel.adjustsFontSizeToFitWidth = true;
// titleLabel.numberOfLines = 3;
// titleLabel.shadowOffset = CGSizeMake(0, -1);
// titleLabel.textAlignment = NSTextAlignmentCenter;
// titleLabel.layer.opacity = 0;
CATextLayer * textLayer = [CATextLayer layer];
textLayer.string = [[IVYSubTitleManager manager] getSRTSubtitleWithCurrentObj:obj];
textLayer.frame = CGRectMake(8, 8, kScreenW - 16, 38);
textLayer.wrapped = YES;
// textLayer.contentsScale = [UIScreen mainScreen].scale;
textLayer.alignmentMode = kCAAlignmentCenter;
textLayer.truncationMode = kCATruncationNone;
textLayer.opacity = 0;
// 这个是透明度动画主要是使在插入的才显示，其它时候都是不显示的
CABasicAnimation *opacityAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
opacityAnim.fromValue = [NSNumber numberWithFloat:1];
opacityAnim.toValue = [NSNumber numberWithFloat:1];
opacityAnim.removedOnCompletion = NO;
CABasicAnimation *opacityDismissAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
opacityDismissAnim.fromValue = [NSNumber numberWithFloat:1];
opacityDismissAnim.toValue = [NSNumber numberWithFloat:0];
opacityDismissAnim.removedOnCompletion = NO;
opacityDismissAnim.beginTime = obj.endTime - obj.startTime;
opacityDismissAnim.duration = 0.1;
CAAnimationGroup *groupAnimation = [CAAnimationGroup animation];
groupAnimation.animations = [NSArray arrayWithObjects:opacityAnim, opacityDismissAnim, nil];
if (obj.startTime == 0) {
groupAnimation.beginTime = 0.01;
} else {
groupAnimation.beginTime = obj.startTime;
}
groupAnimation.duration = obj.endTime - obj.startTime;
[textLayer addAnimation:groupAnimation forKey:@"groupAnimation"];
[parentLayer addSublayer: textLayer];
}
mainCompositionInst.animationTool = [AVVideoCompositionCoreAnimationTool
videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
self.exporter.outputURL = url;
self.exporter.outputFileType = AVFileTypeQuickTimeMovie;
/// 赋值音频
self.exporter.audioMix = videoAudioMixTools;
self.exporter.shouldOptimizeForNetworkUse = YES;
/// 设置字幕 layer层
self.exporter.videoComposition = mainCompositionInst;
__weak typeof(self) wSelf = self;
[self.exporter exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
[SVProgressHUD showWithStatus:@"录制合成完成"];
[wSelf exportDidFinish:wSelf.exporter];
});
}];
}
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