iOS StreamingKit 如何录制/保存音频？

Question

我正在使用 https://github.com/tumtumtum/StreamingKit

用于流式传输实时 url。工作得很好。我想在我的应用程序中添加录音/保存音频功能。有谁知道这个图书馆是否可以做到这一点？如果没有，是否有其他选择？请注意，我需要录制实时流音频，而不是本地文件/静态 url。

该页面显示您可以在播放之前拦截 PCM 数据:

[audioPlayer appendFrameFilterWithName:@"MyCustomFilter" block:^(UInt32 channelsPerFrame, UInt32 bytesPerFrame, UInt32 frameCount, void* frames)
{
   ...
}];

但是，我不确定如何将其转换为实际的录音/mp3 文件，甚至无法从中截取实际数据？

Answer 1

您可以这样做，尽管 StreamingKit 似乎对它提供给您的样本的格式有点保密。采样率是多少？ float 还是整数？我想你可以从样本量中猜出。此示例假定 16 位整数。

NSURL *dstUrl = [[NSURL fileURLWithPath:NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0] ] URLByAppendingPathComponent:@"output.m4a"];

NSLog(@"write to %@", dstUrl);

__block AVAudioFile *audioFile = nil;

[audioPlayer appendFrameFilterWithName:@"MyCustomFilter" block:^(UInt32 channelsPerFrame, UInt32 bytesPerFrame, UInt32 frameCount, void* frames)
 {
     NSError *error;

     // what's the sample rate? StreamingKit doesn't seem to tell us
     double sampleRate = 44100;

     if (!audioFile) {
         NSDictionary *settings =
         @{
           AVFormatIDKey : @(kAudioFormatMPEG4AAC),
           AVSampleRateKey : @(sampleRate),
           AVNumberOfChannelsKey : @(channelsPerFrame),
           };

         // need commonFormat?
         audioFile = [[AVAudioFile alloc] initForWriting:dstUrl settings:settings commonFormat:AVAudioPCMFormatInt16 interleaved:YES error:&error];
         if (!audioFile) {
             // error
         }
     }

     AVAudioFormat *format = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatInt16 sampleRate:sampleRate channels:channelsPerFrame interleaved:YES];
     AVAudioPCMBuffer *buffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:format frameCapacity:frameCount];

     buffer.frameLength = frameCount;
     memmove(buffer.int16ChannelData[0], frames, frameCount*bytesPerFrame);

     if (![audioFile writeFromBuffer:buffer error:&error]) {
         NSLog(@"write error: %@", error);
     }
}];

[self.audioPlayer performSelector:@selector(removeFrameFilterWithName:) withObject:@"MyCustomFilter" afterDelay:10];