我现在正在尝试导出一个播放器使用AVPlayer（使用网址）的mp3文件，因此不必下载两次。
这是我的示例代码：
我已经尝试过每个outputFileType ......
self.exporter = [[AVAssetExportSession alloc] initWithAsset:self.asset presetName:AVAssetExportPresetPassthrough];
}
NSError *error;
NSLog(@"export.supportedFileTypes : %@",self.exporter.supportedFileTypes);
// "com.apple.quicktime-movie",
// "com.apple.m4a-audio",
// "public.mpeg-4",
// "com.apple.m4v-video",
// "public.3gpp",
// "org.3gpp.adaptive-multi-rate-audio",
// "com.microsoft.waveform-audio",
// "public.aiff-audio",
// "public.aifc-audio",
// "com.apple.coreaudio-format"
self.exporter.outputFileType = @"public.aiff-audio";
self.exporter.shouldOptimizeForNetworkUse = YES;
NSURL *a = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:&error];
NSURL *url = [a URLByAppendingPathComponent:@"filename.mp3"];
NSString *filePath = [url absoluteString];
self.exporter.outputURL = url;
if (![[NSFileManager defaultManager] fileExistsAtPath:filePath]){
[self.exporter exportAsynchronouslyWithCompletionHandler:^{
if (self.exporter.status == AVAssetExportSessionStatusCompleted)
{
if (![[NSFileManager defaultManager] fileExistsAtPath:filePath]){
NSLog(@"File doesn't exist at path");
}else {
NSLog@"File saved!");
}
}
else if(self.exporter.status == AVAssetExportSessionStatusFailed){
NSLog(@"Failed");
}else if(self.exporter.status == AVAssetExportSessionStatusUnknown){
NSLog(@"Unknown");
}else if(self.exporter.status == AVAssetExportSessionStatusCancelled){
NSLog(@"Cancelled");
}else if(self.exporter.status == AVAssetExportSessionStatusWaiting){
NSLog(@"Waiting");
}else if(self.exporter.status == AVAssetExportSessionStatusExporting){
NSLog(@"Exporting");
}
NSLog(@"Exporter error! : %@",self.exporter.error);
}];
}}else{
NSLog(@"File already exists at path");
}
如果无法做到这一点，有什么工作吗？
另外，因为我可以更改音频文件的格式。使用AVAudioPlayer的理想类型是什么？
看来AVAssetExportSession只支持使用AVAssetExportPresetPassthrough预设的com.apple.quicktime-movie（.mov）和com.apple.coreaudio-format（.caf）进行mp3转码的文件类型。在编写输出文件时，您还必须确保使用其中一个文件扩展名，否则将无法保存。
支持的输出文件类型和mp3输入文件的扩展名以粗体显示（在OS X 10.11.6上测试）：
如果您不介意将音频数据转换为其他格式，则不必使用AVAssetExportPresetPassthrough预设。还有AVAssetExportPresetLowQuality，AVAssetExportPresetMediumQuality和AVAssetExportPresetHighestQuality。在随后的示例代码中，输出URL具有扩展名.m4a，并且生成的转码在iTunes和其他媒体播放器中播放：
AVAsset * asset = [AVAsset assetWithURL:inputURL];
AVAssetExportSession * exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality];
exportSession.outputFileType = AVFileTypeMPEG4;
exportSession.outputURL = outputURL;
exportSession.metadata = asset.metadata;
[exportSession exportAsynchronouslyWithCompletionHandler:^{
if (exportSession.status == AVAssetExportSessionStatusCompleted)
{
NSLog(@"AV export succeeded.");
}
else if (exportSession.status == AVAssetExportSessionStatusCancelled)
{
NSLog(@"AV export cancelled.");
}
else
{
NSLog(@"AV export failed with error: %@ (%ld)", exportSession.error.localizedDescription, (long)exportSession.error.code);
}
}];
我试图从ipod库导出mp3格式的音频文件。这是我的解决方案。
extension DirectoryListViewController: MPMediaPickerControllerDelegate {
public func mediaPicker(_ mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {
guard let mediaItem = mediaItemCollection.items.first else { ImportExternalFileService.shared.alertImportError(); return }
guard let url = mediaItem.assetURL else { ImportExternalFileService.shared.alertImportError(); return }
guard let songTitle = mediaItem.title else { ImportExternalFileService.shared.alertImportError(); return }
guard let exportSession = AVAssetExportSession(asset: AVURLAsset(url: url), presetName: AVAssetExportPresetAppleM4A) else {
ImportExternalFileService.shared.alertImportError(); return
}
exportSession.outputFileType = .m4a
exportSession.metadata = AVURLAsset(url: url).metadata
exportSession.shouldOptimizeForNetworkUse = true
guard let fileExtension = UTTypeCopyPreferredTagWithClass(exportSession.outputFileType!.rawValue as CFString, kUTTagClassFilenameExtension) else {
ImportExternalFileService.shared.alertImportError(); return
}
let documentURL = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
let outputURL = documentURL.appendingPathComponent("\(songTitle).\(fileExtension.takeUnretainedValue())")
/* Dont't forget to remove the existing url, or exportSession will throw error: can't save file */
do {
try FileManager.default.removeItem(at: outputURL)
} catch let error as NSError {
print(error.debugDescription)
}
exportSession.outputURL = outputURL
exportSession.exportAsynchronously(completionHandler: {
if exportSession.status == .completed {
DispatchQueue.main.async {
ImportExternalFileService.shared.importRecordFile(url: exportSession.outputURL!)
}
} else {
print("AV export failed with error:- ", exportSession.error!.localizedDescription)
}
})
}
public func mediaPickerDidCancel(_ mediaPicker: MPMediaPickerController) {
dismiss(animated: true, completion: nil)
}
}