Xcode：如何将MP4文件转换为音频文件 [英] Xcode: How to convert MP4-File to Audio-File

问题描述

我想将MP4文件从apps文件夹转换为音频文件（mp3或m4a）。
我已经试过，但是我不能用AVPlayer播放转换后的MP3文件。

这是我的代码：

   - （void）convertMP4toMP3withFile：（NSString *）dstPath 
 {
 NSURL * dstURL = [NSURL fileURLWithPath：dstPath]; 
 
 AVMutableComposition * newAudioAsset = [AVMutableComposition构成]; 
 
 AVMutableCompositionTrack * dstCompositionTrack; 
 dstCompositionTrack = [newAudioAsset addMutableTrackWithMediaType：AVMediaTypeAudio preferredTrackID：kCMPersistentTrackID_Invalid]; 
 
 AVAsset * srcAsset = [AVURLAsset URLAssetWithURL：dstURL options：nil]; 
 AVAssetTrack * srcTrack = [[srcAsset tracksWithMediaType：AVMediaTypeAudio] objectAtIndex：0]; 
 
 
 CMTimeRange timeRange = srcTrack.timeRange; 
 
 NSError *错误; 
 
 if（NO == [dstCompositionTrack insertTimeRange：timeRange ofTrack：srcTrack atTime：kCMTimeZero error& error]）{
 NSLog（@track insert failed：％@ \\\
 ，错误）; 
 return; 
 
 
 $ b AVAssetExportSession * exportSesh = [[AVAssetExportSession alloc] initWithAsset：newAudioAsset presetName：AVAssetExportPresetPassthrough]; 
 
 exportSesh.outputFileType = AVFileTypeAppleM4A; 
 exportSesh.outputURL = dstURL; 
 
 [[NSFileManager defaultManager] removeItemAtURL：dstURL error：nil]; 
 
 [exportSesh exportAsynchronouslyWithCompletionHandler：^ {
 AVAssetExportSessionStatus status = exportSesh.status; 
 NSLog（@exportAsynchronouslyWithCompletionHandler：％i \\\
，status）; 
 
 if（AVAssetExportSessionStatusFailed == status）{
 NSLog（@FAILURE：％@ \\\
，exportSesh.error）; 
} else if（AVAssetExportSessionStatusCompleted == status）{
 NSLog（@SUCCESS！\\\
）; 
 
 
 NSError *错误; 
 //以
 
的格式附加文件的名称//检查文件是否存在（完全不必要）。 
 NSString * onlyPath = [dstPath stringByDeletingLastPathComponent]; 
 NSString * toPathString = [NSString stringWithFormat：@％@ / testfile.m4a，onlyPath]; 
 [[NSFileManager defaultManager] moveItemAtPath：dstPath toPath：toPathString error：& error]; 
 [self loadFiles]; 
} 
}]; 
 
 
 
 
 
 $ b 
有没有人可以解决我的问题，或者可以改善我的代码？
解决方案
替换此行： 
 
 
  exportSesh.outputFileType = AVFileTypeAppleM4A; 
  
： 
 
 
  exportSesh.outputFileType = AVFileTypeCoreAudioFormat; 
  
&这： 
 
 
  NSString * toPathString = [NSString stringWithFormat：@％@ / testfile.m4a，onlyPath]; 
  
： 
 
 
  NSString * toPathString = [NSString stringWithFormat：@％@ / testfile.mp3，onlyPath]; 
  
为我工作：）
I want to convert a MP4-file from the apps Document folder into an Audio-file (mp3 or m4a).
I already tried, but i can not play the converted MP3-file with AVPlayer.


Here is my code:
-(void)convertMP4toMP3withFile:(NSString*)dstPath
{
    NSURL *dstURL = [NSURL fileURLWithPath:dstPath];

AVMutableComposition*   newAudioAsset = [AVMutableComposition composition];

AVMutableCompositionTrack*  dstCompositionTrack;
dstCompositionTrack = [newAudioAsset addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

AVAsset*    srcAsset = [AVURLAsset URLAssetWithURL:dstURL options:nil];
AVAssetTrack*   srcTrack = [[srcAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];


CMTimeRange timeRange = srcTrack.timeRange;

NSError*    error;

if(NO == [dstCompositionTrack insertTimeRange:timeRange ofTrack:srcTrack atTime:kCMTimeZero error:&error]) {
    NSLog(@"track insert failed: %@\n", error);
    return;
}


AVAssetExportSession*   exportSesh = [[AVAssetExportSession alloc] initWithAsset:newAudioAsset presetName:AVAssetExportPresetPassthrough];

exportSesh.outputFileType = AVFileTypeAppleM4A;
exportSesh.outputURL = dstURL;

[[NSFileManager defaultManager] removeItemAtURL:dstURL error:nil];

[exportSesh exportAsynchronouslyWithCompletionHandler:^{
    AVAssetExportSessionStatus  status = exportSesh.status;
    NSLog(@"exportAsynchronouslyWithCompletionHandler: %i\n", status);

    if(AVAssetExportSessionStatusFailed == status) {
        NSLog(@"FAILURE: %@\n", exportSesh.error);
    } else if(AVAssetExportSessionStatusCompleted == status) {
        NSLog(@"SUCCESS!\n");


        NSError *error;
        //append the name of the file in jpg form

        //check if the file exists (completely unnecessary).
        NSString *onlyPath = [dstPath stringByDeletingLastPathComponent];
        NSString *toPathString = [NSString stringWithFormat:@"%@/testfile.m4a", onlyPath];
        [[NSFileManager defaultManager] moveItemAtPath:dstPath toPath:toPathString error:&error];
        [self loadFiles];
    }
}];
}
Has anyone a solution for my problem or can improve my code?
解决方案
replace this line:
exportSesh.outputFileType = AVFileTypeAppleM4A;
with:
exportSesh.outputFileType = AVFileTypeCoreAudioFormat;
& this: 
NSString *toPathString = [NSString stringWithFormat:@"%@/testfile.m4a", onlyPath];
with:
NSString *toPathString = [NSString stringWithFormat:@"%@/testfile.mp3", onlyPath];
Worked for me :)

                        
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