Question

我尝试从iPod-Library导出音频文件。我的目标是使用此iPod-Library文件在应用程序文档文件夹中创建新文件。它无法仅为某些项目创建文件。以下是我的代码段。

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

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];

AVAssetExportSession *exporter = [[AVAssetExportSession alloc]
                                  initWithAsset: songAsset
                                  presetName: AVAssetExportPresetAppleM4A];

exporter.outputFileType = @"com.apple.m4a-audio";

NSString *songName  =   [filename stringByAppendingString:@".m4a"];

NSString *musicfilepath  = [documentsDirectory stringByAppendingPathComponent:@"musics/"];

[[NSFileManager defaultManager] createDirectoryAtPath:musicfilepath withIntermediateDirectories:YES attributes:nil error:nil];

NSString *exportFile = [musicfilepath stringByAppendingPathComponent:songName];



NSError *error1;

if([[NSFileManager defaultManager] fileExistsAtPath:exportFile]) 
{

    [[NSFileManager defaultManager] removeItemAtPath:exportFile error:&error1];

}

NSURL* exportURL = [[NSURL fileURLWithPath:exportFile] retain];

exporter.outputURL = exportURL;

使用错误处理程序块尝试时，如下所示出现错误：

    [exporter exportAsynchronouslyWithCompletionHandler:^{

    int exportStatus = exporter.status;

    switch (exportStatus) {

        case AVAssetExportSessionStatusFailed: {

            NSError *exportError = exporter.error;

            NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);

            break;
        }
  }
 }];

AVAssetExportSessionStatusFailed：错误域= AVFoundationErrorDomain代码= -11800＆＃34;操作无法完成＆＃34; UserInfo = 0x214f20 {NSLocalizedFailureReason =发生未知错误（-12124），NSUnderlyingError = 0x218270＆＃34;操作无法完成。（OSStatus错误-12124。）＆＃34;，NSLocalizedDescription =操作无法完成}

Answer 1

自己玩了很多，一些答案可能是相关和正确的。需要注意的另一件事是，如果尝试组合具有不同帧速率的视频，我经常会遇到类似的AVFoundation错误。检查源文件的帧速率并检查CMTime。在将某些文件添加到AVMutableComposition之前，您可能需要对其进行预处理。

Answer 2

如果您启用了iTunes匹配并且文件未下载到设备，则可能会发生这种情况。你能检查一下你的情况吗？如果是这样，我可以提供代码来检测它。

+ (BOOL)isDownloadedFromiCloud:(MPMediaItem *)item {
    if ([item valueForProperty:MPMediaItemPropertyAssetURL] != nil) {
        AVURLAsset *asset = [AVURLAsset assetWithURL:[item valueForProperty:MPMediaItemPropertyAssetURL]];
        if (asset.exportable)
            return YES;
    }

    return NO;
}

Answer 3

我也经历过这一点。你在使用iTunes匹配吗？可能是该文件不在实际设备上。您可以通过检查hasProtectedContent或确保exportable为YES等属性在AVAsset上进行检查。

另外，我注意到您正在使用AVExportSession预设AVAssetExportPresetAppleM4A'. This will re-encode the file you are exporting. It may be easier (and much faster) to just pass-though instead using AVAssetExportPresetPassthrough`。这假设您对现有的文件格式感到满意，可能是.m4a，.mp3，.wav等......

Answer 4

您正在使用的音乐文件路径可能有误。试试这个

NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, 

NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0]; 
documentsDirectory = [documentsDirectory stringByAppendingPathComponent:@"Music"];
NSError* error;
if (![[NSFileManager defaultManager] fileExistsAtPath:documentsDirectory])
    [[NSFileManager defaultManager] createDirectoryAtPath:documentsDirectory                withIntermediateDirectories:NO attributes:nil error:&error]; 

NSString *exportFile = [documentsDirectory stringByAppendingPathComponent:songName];

if([[NSFileManager defaultManager] fileExistsAtPath:exportFile]) 
{

    [[NSFileManager defaultManager] removeItemAtPath:exportFile error:&error1];

}

if (error != nil) {
NSURL* exportURL = [[NSURL fileURLWithPath:exportFile] retain];

exporter.outputURL = exportURL; 
[exporter exportAsynchronouslyWithCompletionHandler:^{

int exportStatus = exporter.status;

switch (exportStatus) {

    case AVAssetExportSessionStatusFailed: {

        NSError *exportError = exporter.error;

        NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);

        break;
        }
    }
  }
];
}

某些文件的AVAssetExport失败

4 个答案: