[英]Error in extracting audio from .m4v video file
我正在嘗試從.m4v視頻中提取音頻文件。 它顯示錯誤,如,
Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo=0x15e350d0 {NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x15d1c6b0 "The operation couldn’t be completed. (OSStatus error -12124.)", NSLocalizedFailureReason=An unknown error occurred (-12124)}
這是我的代碼:
-(void)extractAudioFromVideo{
//Create a audia composition and add audio track
AVMutableComposition *newAudioAsset = [AVMutableComposition composition];
AVMutableCompositionTrack *dstCompositionTrack = [newAudioAsset addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
//Get video asset from which the audio should be extracted
NSURL *url = [[NSBundle mainBundle] URLForResource:@"sample_iPod" withExtension:@"m4v"];
AVAsset *srcAsset = [AVAsset assetWithURL:url];
NSArray *trackArray = [srcAsset tracksWithMediaType:AVMediaTypeAudio];
if(!trackArray.count){
NSLog(@"Track returns empty array for mediatype AVMediaTypeAudio");
return;
}
AVAssetTrack *srcAssetTrack = [trackArray objectAtIndex:0];
//Extract time range
CMTimeRange timeRange = srcAssetTrack.timeRange;
//Insert audio from the video to mutable avcomposition track
NSError *err = nil;
if(NO == [dstCompositionTrack insertTimeRange:timeRange ofTrack:srcAssetTrack atTime:kCMTimeZero error:&err]){
NSLog(@"Failed to insert audio from the video to mutable avcomposition track");
return;
}
//Export the avcompostion track to destination path
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex: 0];
NSString *dstPath = [documentsDirectory stringByAppendingString:@"sample_audio.mp4"];
NSURL *dstURL = [NSURL fileURLWithPath:dstPath];
//Remove if any file already exists
[[NSFileManager defaultManager] removeItemAtURL:dstURL error:nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:newAudioAsset presetName:AVAssetExportPresetPassthrough];
NSLog(@"support file types= %@", [exportSession supportedFileTypes]);
exportSession.outputFileType = @"public.mpeg-4";
exportSession.outputURL = dstURL;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
AVAssetExportSessionStatus status = exportSession.status;
if(AVAssetExportSessionStatusCompleted != status){
NSLog(@"Export status not yet completed. Error: %@", exportSession.error.description);
}
}];
}
我該如何解決這個錯誤?
我已經在模擬器中測試了你的代碼。 它在模擬器(IOS7)中運行良好。 但是當我在iPodTouch-5上運行時,它會像你提到的那樣顯示錯誤。 花了超過15分鍾,發現和愚蠢的錯誤。
我在Device中運行時獲取如下路徑( Documentssample_audio.mp4
)
@"file:///var/mobile/Applications/A1E1D85F-0198-4A0C-80F8-222F0DA1C31A/Documentssample_audio.mp4"
所以我修改了路徑...
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex: 0];
NSString *dstPath = [documentsDirectory stringByAppendingString:@"/sample_audio.mp4"];
現在我得到如下路徑( /Documents/sample_audio.mp4
)並正常工作。 但我不知道,它是如何發生的
@"file:///var/mobile/Applications/A1E1D85F-0198-4A0C-80F8-222F0DA1C31A/Documents/sample_audio.mp4"
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