Ios AVMutableComposition减少最终视频的大小和分辨率

我用一组图像创建了一个视频

它成功创建了视频，然后我将音频添加到创建的视频文件中

我创建AVMuatableComposition对象，通过创建AVAssetTracks添加视频和音频，最后在AvassetExportSession的帮助下导出为单个视频文件

假设第一个没有音频的视频是vdo.mp4，final（添加音频后）是final.mp4，那么my final.mp4的大小和分辨率都低于vdo.mp4

这是我的代码，它结合了这两个文件

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSError * error = nil;

AVMutableComposition * composition = [AVMutableComposition composition];

NSURL *url = [NSURL fileURLWithPath:filePath];

AVURLAsset * videoAsset = [AVURLAsset URLAssetWithURL:url options:nil];

AVAssetTrack * videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                            preferredTrackID: kCMPersistentTrackID_Invalid];

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,videoAsset.duration) ofTrack:videoAssetTrack atTime:kCMTimeZero error:&error];

CMTime audioStartTime = kCMTimeZero;
for (   NSInteger i = 0;i< [mArrAudioFileNames count];i++ )
{
    NSString *audioFileName = nil;
    NSString *docsDir = nil;
    if ( [mArrAudioFileNames objectAtIndex:i] != [NSNull null]) {
        audioFileName = [mArrAudioFileNames objectAtIndex:i];
        docsDir = [[self dataFolderPathForAudio] stringByAppendingPathComponent:audioFileName];

    }else{
        //audioFileName = @" ";
        docsDir = [[NSBundle mainBundle] pathForResource:@"sample" ofType:@"mp3"];
    }

    // NSString *docsDir = [[self dataFolderPathForAudio] stringByAppendingPathComponent:audioFileName];
    AVURLAsset * urlAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:docsDir] options:nil];

    AVAssetTrack * audioAssetTrack = [[urlAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                                preferredTrackID: kCMPersistentTrackID_Invalid];

    [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,urlAsset.duration) ofTrack:audioAssetTrack atTime:audioStartTime error:&error];

    Float64 duration = CMTimeGetSeconds(urlAsset.duration);

    audioStartTime = CMTimeAdd(audioStartTime, CMTimeMake((int) ((duration * kRecordingFPS) + 0.5), kRecordingFPS));
}

AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality];
//assetExport.videoComposition = compositionVideoTrack;

 assetExport.outputFileType = AVFileTypeQuickTimeMovie;// @"com.apple.quicktime-movie";
assetExport.outputURL = [NSURL fileURLWithPath:outFilePath];

[assetExport exportAsynchronouslyWithCompletionHandler:
 ^(void ) {
     switch (assetExport.status)
     {
         case AVAssetExportSessionStatusCompleted:
             //                export complete
             NSLog(@"Export Complete");
             [self performSelectorOnMainThread:@selector(creatingVideoDone:)
                                    withObject:outFilePath waitUntilDone:NO];
             [assetExport release];
             break;
         case AVAssetExportSessionStatusFailed:
             NSLog(@"Export Failed");
             NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
             // Set delegate to move to view
             if ( mDelegate!= nil && [mDelegate respondsToSelector:@selector(errorAlert:)])
             {
                 [self performSelectorOnMainThread:@selector(errorOccured:)
                                        withObject:[assetExport.error
                                                    localizedDescription]
                                     waitUntilDone:NO];
             }
             [assetExport release];
             break;
         case AVAssetExportSessionStatusCancelled:
             NSLog(@"Export Failed");
             NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
             // Set delegate to move to view
             if ( mDelegate!= nil && [mDelegate respondsToSelector:@selector(errorAlert:)])
             {
                 [self performSelectorOnMainThread:@selector(errorOccured:)
                                        withObject:[assetExport.error
                                                    localizedDescription]
                                     waitUntilDone:NO];
             }
             [assetExport release];
             break;
     }
 }];

NSAutoreleasePool*pool=[[NSAutoreleasePool alloc]init]；
n错误*错误=nil；
AVMutableComposition*composition=[AVMutableComposition]；
NSURL*url=[NSURL fileURLWithPath:filePath]；
AVURLAsset*videoAsset=[AVURLAsset UrlAssetTwithUrl:url选项：无]；
AVAssetTrack*videoAssetTrack=[[videoAsset tracksWithMediaType:AVMediaTypeVideo]对象索引：0]；
AVMutableCompositionTrack*compositionVideoTrack=[composition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCompersistentTrackID_无效]；
[compositionVideoTrack insertTimeRange:CMTimeRangeMake（kCMTimeZero，videoAsset.duration）of Track:videoAssetTrack atTime:kCMTimeZero错误：&错误]；
CMTime audioStartTime=kCMTimeZero；
对于（NSInteger i=0；i<[marraAudioFileNames计数]；i++）
{
NSString*audioFileName=nil；
NSString*docsDir=nil；
if（[mArrAudioFileNames对象索引：i]！=[NSNull]）{
audioFileName=[mArrAudioFileNames对象索引：i]；
docsDir=[[self-dataFolderPathForAudio]stringByAppendingPathComponent:audioFileName]；
}否则{
//audioFileName=@；
docsDir=[[NSBundle mainBundle]pathForResource:@“mp3”类型的“sample”；
}
//NSString*docsDir=[[self-dataFolderPathForAudio]stringByAppendingPathComponent:audioFileName]；
AVURLAsset*urlAsset=[AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:docsDir]选项：nil]；
AVAssetTrack*audioAssetTrack=[[urlAsset tracksWithMediaType:AVMediaTypeAudio]对象索引：0]；
AVMutableCompositionTrack*compositionAudioTrack=[CompositionAddMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCompersistentTrackID_无效]；
[compositionAudioTrack insertTimeRange:CMTimeRangeMake（kCMTimeZero，urlAsset.duration）of Track:audioAssetTrack atTime:audioStartTime错误：&error]；
Float64 duration=CMTimeGetSeconds（urlAsset.duration）；
audioStartTime=CMTimeAdd（audioStartTime，CMTimeMake（（int）（（持续时间*kRecordingFPS）+0.5），kRecordingFPS））；
}
AVAssetExportSession*assetExport=[[AVAssetExportSession alloc]initWithAsset:composition预设名称：AVAssetExportPresetMediumQuality]；
//assetExport.videoComposition=合成视频跟踪；
assetExport.outputFileType=AVFileTypeQuickTimeMovie；//@“com.apple.quicktime电影”；
assetExport.outputURL=[NSURL fileURLWithPath:outFilePath]；
[assetExport exportAsynchronouslyWithCompletionHandler:
^（无效）{
交换机（assetExport.status）
{
案例AvassetExportSessionStatus已完成：
//出口完成
NSLog（“导出完成”）；
[self-performSelectorOnMainThread:@selector（creatingVideoDone:）
withObject:outFilePath waitUntilDone:NO]；
[港口放行]；
打破
案例AvassetExportSessionStatus失败：
NSLog（@“导出失败”）；
NSLog（@“ExportSessionError:%@，[assetExport.error localizedDescription]）；
//将委托设置为移动到视图
if（mDelegate！=nil&&[mDelegate respondsToSelector:@selector（errorAlert:）]））
{
[self-performSelectorOnMainThread:@selector（发生错误：）
withObject:[assetExport.error
本地化描述]
waitUntilDone：没有]；
}
[港口放行]；
打破
案例AvassetExportSessionStatus取消：
NSLog（@“导出失败”）；
NSLog（@“ExportSessionError:%@，[assetExport.error localizedDescription]）；
//将委托设置为移动到视图
if（mDelegate！=nil&&[mDelegate respondsToSelector:@selector（errorAlert:）]））
{
[self-performSelectorOnMainThread:@selector（发生错误：）
withObject:[assetExport.error
本地化描述]
waitUntilDone：没有]；
}
[港口放行]；
打破
}
}];

感谢您的帮助

---

谢谢。

您是否尝试过其他值而不是AvassetExportPresetMediumQuality是的。我还使用了AVAssetExportPresetHighestQuality值。它确实增加了最终输出文件的大小（数据），但分辨率不同。是否还有指定宽度和高度的方法？@subhashAmale找到了用宽度和高度调整大小的答案？