裁剪音頻文件

Question

我想在iOS中實現音頻裁剪，我想要一個類似於雙向滑塊的東西，用戶可以在特定的錄製音頻週期內滑動，然後我會將該音頻存儲在以下

Answer 1

AVAssetExportSession - 導出修剪音頻資產

下面的代碼會爲你做，請參閱本link作進一步詳細的工作

- (BOOL)exportAsset:(AVAsset *)avAsset toFilePath:(NSString *)filePath { 

    // we need the audio asset to be at least 50 seconds long for this snippet 
    CMTime assetTime = [avAsset duration]; 
    Float64 duration = CMTimeGetSeconds(assetTime); 
    if (duration < 50.0) return NO; 

    // get the first audio track 
    NSArray *tracks = [avAsset tracksWithMediaType:AVMediaTypeAudio]; 
    if ([tracks count] == 0) return NO; 

    AVAssetTrack *track = [tracks objectAtIndex:0]; 

    // create the export session 
    // no need for a retain here, the session will be retained by the 
    // completion handler since it is referenced there 
    AVAssetExportSession *exportSession = [AVAssetExportSession 
              exportSessionWithAsset:avAsset 
              presetName:AVAssetExportPresetAppleM4A]; 
    if (nil == exportSession) return NO; 

    // create trim time range - 20 seconds starting from 30 seconds into the asset 
    CMTime startTime = CMTimeMake(30, 1); 
    CMTime stopTime = CMTimeMake(50, 1); 
    CMTimeRange exportTimeRange = CMTimeRangeFromTimeToTime(startTime, stopTime); 

    // create fade in time range - 10 seconds starting at the beginning of trimmed asset 
    CMTime startFadeInTime = startTime; 
    CMTime endFadeInTime = CMTimeMake(40, 1); 
    CMTimeRange fadeInTimeRange = CMTimeRangeFromTimeToTime(startFadeInTime, 
                  endFadeInTime); 

    // setup audio mix 
    AVMutableAudioMix *exportAudioMix = [AVMutableAudioMix audioMix]; 
    AVMutableAudioMixInputParameters *exportAudioMixInputParameters = 
      [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:track]; 

    [exportAudioMixInputParameters setVolumeRampFromStartVolume:0.0 toEndVolume:1.0 
            timeRange:fadeInTimeRange]; 
    exportAudioMix.inputParameters = [NSArray 
             arrayWithObject:exportAudioMixInputParameters]; 

    // configure export session output with all our parameters 
    exportSession.outputURL = [NSURL fileURLWithPath:filePath]; // output path 
    exportSession.outputFileType = AVFileTypeAppleM4A; // output file type 
    exportSession.timeRange = exportTimeRange; // trim time range 
    exportSession.audioMix = exportAudioMix; // fade in audio mix 

    // perform the export 
    [exportSession exportAsynchronouslyWithCompletionHandler:^{ 

     if (AVAssetExportSessionStatusCompleted == exportSession.status) { 
      NSLog(@"AVAssetExportSessionStatusCompleted"); 
     } else if (AVAssetExportSessionStatusFailed == exportSession.status) { 
      // a failure may happen because of an event out of your control 
      // for example, an interruption like a phone call comming in 
      // make sure and handle this case appropriately 
      NSLog(@"AVAssetExportSessionStatusFailed"); 
     } else { 
      NSLog(@"Export Session Status: %d", exportSession.status); 
     } 
    }]; 

    return YES; 
}