如何使用AVAssetExportSession导出AVPlayer音频mp3文件？ [英] How can I export a AVPlayer audio mp3 file using AVAssetExportSession?

问题描述

我现在正在尝试导出一个使用AVPlayer（使用网址）播放器的mp3文件，因此不必下载两次。

I am now trying to export an mp3 file that has been player using AVPlayer (using an url) so it doesn't have to be downloaded twice.

这是我的示例代码：

我已尝试过每个outputFileType ...

I've tried every 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");
        }

如果无法完成，有什么工作吗？

If this is not possible to accomplish, is there any work around?

另外，因为我可以改变音频文件的格式。什么是使用AVAudioPlayer的理想类型？

Also, as I can change the format of the audio file. What's the ideal type to work with AVAudioPlayer?

推荐答案

它出现 AVAssetExportSession 仅使用<$ c $支持使用 com.apple.quicktime-movie （。mov）和 com.apple.coreaudio-format （.caf）进行mp3转码的文件类型c> AVAssetExportPresetPassthrough 预设。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。

It appears AVAssetExportSession only supports filetypes for mp3 transcoding with com.apple.quicktime-movie (.mov) and com.apple.coreaudio-format (.caf) using the AVAssetExportPresetPassthrough preset. You must also be sure to use one of these file extensions when writing your output file otherwise it won't save.

支持的输出文件类型和mp3输入文件的扩展名为粗体（在OS X 10.11.6上测试）：

Supported output filetype and extensions for an mp3 input file are in bold (tested on OS X 10.11.6):

• com.apple.quicktime-movie（.mov）


• com.apple.m4a-audio（.m4a）


• public.mpeg-4（.mp4）


• com.apple.m4v-video（.m4v）


• org.3gpp.adaptive-multi-rate-audio（.amr）


• com.microsoft.waveform-audio（.wav）


• public.aiff-audio（.aiff）


• public.aifc-audio （.aifc）


• com.apple.coreaudio-format（.caf）

• com.apple.quicktime-movie (.mov)
• com.apple.m4a-audio (.m4a)
• public.mpeg-4 (.mp4)
• com.apple.m4v-video (.m4v)
• org.3gpp.adaptive-multi-rate-audio (.amr)
• com.microsoft.waveform-audio (.wav)
• public.aiff-audio (.aiff)
• public.aifc-audio (.aifc)
• com.apple.coreaudio-format (.caf)

如果您不介意将音频数据的正确转码转换为其他格式，则您不必使用 AVAssetExportPresetPassthrough 预设。还有 AVAssetExportPresetLowQuality ， AVAssetExportPresetMediumQuality 和 AVAssetExportPresetHighestQuality 。在随后的示例代码中，输出网址的扩展名为 .m4a ，结果转码在iTunes和其他媒体播放器中播放：

If you don't mind performing a proper transcode of the audio data to another format, then you don't have to use the AVAssetExportPresetPassthrough preset. There are also AVAssetExportPresetLowQuality, AVAssetExportPresetMediumQuality, and AVAssetExportPresetHighestQuality. In the sample code that follows, the output URL has extension .m4a and the resulting transcode plays in iTunes and other media players:

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);
    }
}];

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