我必须在视频文件中进行“慢动作”以及一些帧之间的音频,并且需要将斜视视频存储为新的视频.
参考号：http://www.youtube.com/watch?v=BJ3_xMGzauk(从0到10秒钟)
从我的分析,我发现AVFoundation框架可以是有帮助的.
参考：
http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html
从上述链接复制并粘贴：
“
编辑
AV基金会使用组合从现有的媒体(通常是一个或多个视频和音轨)创建新的资产.您使用可变组合来添加和删除曲目,并调整其时间顺序.您还可以设置音轨的相对音量和斜坡;并设置视频轨道的不透明度和不透明度斜坡.一个组合是在记忆体中保存的一组媒体.使用导出会话导出作品时,它会折叠到一个文件.
在iOS 4.1及更高版本上,您还可以使用资产编写器从介质(如样本缓冲区或静态图像)创建资源.
“
问题：
可以使用AVFoundation框架做“慢动作”视频/音频文件吗？还是有其他包装可用吗？如果我想单独处理音视频,请指导我怎么办？
AV导出会话更新::代码：
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
Nsstring *outputURL = paths[0];
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:outputURL withIntermediateDirectories:YES attributes:nil error:nil];
outputURL = [outputURL stringByAppendingPathComponent:@"output.mp4"];
// Remove Existing File
[manager removeItemAtPath:outputURL error:nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:self.inputAsset presetName:AVAssetExportPresetLowQuality];
exportSession.outputURL = [NSURL fileURLWithPath:outputURL]; // output path;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
[exportSession exportAsynchronouslyWithCompletionHandler:^(void) {
if (exportSession.status == AVAssetExportSessionStatusCompleted) {
[self writeVideoToPhotoLibrary:[NSURL fileURLWithPath:outputURL]];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library writeVideoAtPathToSavedPhotosAlbum:[NSURL fileURLWithPath:outputURL] completionBlock:^(NSURL *assetURL,NSError *error){
if (error) {
NSLog(@"Video Could not be saved");
}
}];
} else {
NSLog(@"error: %@",[exportSession error]);
}
}];
解决方法
您可以使用AVFoundation和CoreMedia框架来缩放视频.
看看AVMutableCompositionTrack方法：
看看AVMutableCompositionTrack方法：
- (void)scaleTimeRange:(CMTimeRange)timeRange toDuration:(CMTime)duration;
样品：
AVURLAsset* videoAsset = nil; //self.inputAsset;
//create mutable composition
AVMutableComposition *mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
NSError *videoInsertError = nil;
BOOL videoInsertResult = [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,videoAsset.duration)
ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
atTime:kCMTimeZero
error:&videoInsertError];
if (!videoInsertResult || nil != videoInsertError) {
//handle error
return;
}
//slow down whole video by 2.0
double videoScaleFactor = 2.0;
CMTime videoDuration = videoAsset.duration;
[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero,videoDuration)
toDuration:CMTimeMake(videoDuration.value*videoScaleFactor,videoDuration.timescale)];
//export
AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition
presetName:AVAssetExportPresetLowQuality];
(也许也可以将来自videoAsset的音轨添加到mixComposition中)