Cocoa touch 使用iOS修剪音频

我想实现一个功能，允许用户修剪他录制的音频文件（.caf）。录音部分已经可以工作了，但是我如何添加一个类似Voicememos应用程序中的微调功能呢。苹果使用的音频微调器有api吗？

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任何帮助都很好…

使用AVFoundation怎么样？将音频文件导入AVAsset（合成等），然后您可以将其导出到文件中（设置首选时间+持续时间）

我不久前写了一个stock函数，它将资产导出到文件中，您还可以指定audiomix。如下所示，它导出所有文件，但您可以将NSTimeRange添加到exporter.timeRange，然后就可以了。虽然我还没有测试过，但应该有效（？）。另一种选择是在创建AVAsset+轨迹时调整时间范围。当然，出口商只处理m4a（AAC）。如果这不是你想要的，很抱歉

-(void)exportAsset:(AVAsset*)asset toFile:(NSString*)filename overwrite:(BOOL)overwrite withMix:(AVAudioMix*)mix {
//NSArray* availablePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:asset];

AVAssetExportSession* exporter = [AVAssetExportSession exportSessionWithAsset:asset presetName:AVAssetExportPresetAppleM4A];

if (exporter == nil) {
    DLog(@"Failed creating exporter!");
    return;
}

DLog(@"Created exporter! %@", exporter);

// Set output file type
DLog(@"Supported file types: %@", exporter.supportedFileTypes);
for (NSString* filetype in exporter.supportedFileTypes) {
    if ([filetype isEqualToString:AVFileTypeAppleM4A]) {
        exporter.outputFileType = AVFileTypeAppleM4A;
        break;
    }
}
if (exporter.outputFileType == nil) {
    DLog(@"Needed output file type not found? (%@)", AVFileTypeAppleM4A);
    return;
}

// Set outputURL
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* parentDir = [NSString stringWithFormat:@"%@/", [paths objectAtIndex:0]];

NSString* outPath = [NSString stringWithFormat:@"%@%@", parentDir, filename];

NSFileManager* manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:outPath]) {
    DLog(@"%@ already exists!", outPath);
    if (!overwrite) {
        DLog(@"Not overwriting, uh oh!");
        return;
    }
    else {
        // Overwrite
        DLog(@"Overwrite! (delete first)");
        NSError* error = nil;
        if (![manager removeItemAtPath:outPath error:&error]) {
            DLog(@"Failed removing %@, error: %@", outPath, error.description);
            return;
        }
        else {
            DLog(@"Removed %@", outPath);
        }
    }
}

NSURL* const outUrl = [NSURL fileURLWithPath:outPath];
exporter.outputURL = outUrl;
// Specify a time range in case only part of file should be exported
//exporter.timeRange =

if (mix != nil)
    exporter.audioMix = mix; // important

DLog(@"Starting export! (%@)", exporter.outputURL);
[exporter exportAsynchronouslyWithCompletionHandler:^(void) {
    // Export ended for some reason. Check in status
    NSString* message;
    switch (exporter.status) {
        case AVAssetExportSessionStatusFailed:
            message = [NSString stringWithFormat:@"Export failed. Error: %@", exporter.error.description];
            DLog(@"%@", message);
            [self showAlert:message];
            break;
        case AVAssetExportSessionStatusCompleted: {
            /*if (playfileWhenExportFinished) {
             DLog(@"playfileWhenExportFinished!");
             [self playfileAfterExport:exporter.outputURL];
             playfileWhenExportFinished = NO;
             }*/
            message = [NSString stringWithFormat:@"Export completed: %@", filename];
            DLog(@"%@", message);
            [self showAlert:message];
            break;
        }
        case AVAssetExportSessionStatusCancelled:
            message = [NSString stringWithFormat:@"Export cancelled!"];
            DLog(@"%@", message);
            [self showAlert:message];
            break;
        default:
            DLog(@"Export unhandled status: %d", exporter.status);
            break;
    }       
}];
}

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以上@Jonny的答案是正确的。在这里，我添加了AudioMixer的使用，以添加音频修剪时的淡入效果

输出：音频资源修剪为20秒，淡入10秒。 在代码段中设置的修剪在30秒时发生 资产的标记，因此跟踪持续时间应至少为 50秒

-（BOOL）exportAssettoFilePath:（NSString*）文件路径{
NSString*inputFilePath=；
NSURL*videoToTrimURL=[NSURL fileURLWithPath:inputFilePath]；
AVAsset*AVAsset=[AVAsset AssetWithur:videoToTrimURL]；
//对于这个片段，我们需要音频资源至少有50秒长
CMTime assetTime=[avAsset duration]；
Float64持续时间=CMTimeGetSeconds（assetTime）；
如果（持续时间<50.0）返回否；
//获取第一个音频曲目
NSArray*曲目=[avAsset tracks SwithMediaType:AVMediaTypeAudio]；
如果（[tracks count]==0）返回否；
AVAssetTrack*track=[tracks objectAtIndex:0]；
//创建导出会话
//此处无需保留，会话将由
//完成处理程序，因为它在那里被引用
AVAssetExportSession*exportSession=[AVAssetExportSession
exportSessionWithAsset:avAsset
预设名称：AVAssetExportPresetAppleM4A]；
if（nil==exportSession）返回NO；
//创建修剪时间范围-从30秒开始到资源中的20秒
CMTime startTime=CMTimeMake（30,1）；
CMTime stopTime=CMTimeMake（50,1）；
CMTimeRange exportTimeRange=CMTimeRangeFromTimeToTime（开始时间、停止时间）；
//创建淡入时间范围-从修剪后的资源开始10秒
CMTime startFadeInTime=开始时间；
CMTime endFadeInTime=CMTimeMake（40,1）；
CMTimeRange fadeInTimeRange=CMTimeRangeFromTimeToTime（startFadeInTime，
endFadeInTime）；
//设置音频混音
AVMutableAudioMix*exportAudioMix=[AVMutableAudioMix audioMix]；
AVMutableAudioMixInputParameters*exportAudioMixInputParameters=
[AVMutableAudioMixInputParameters AudioMixInputParameters SwithTrack:track]；
[exportAudioMixInputParameters setVolumeRampFromStartVolume:0.0到EndVolume:1.0
时间范围：fadeInTimeRange]；
exportAudioMix.inputParameters=[NSArray
arrayWithObject:exportAudioMixInputParameters]；
//使用所有参数配置导出会话输出
exportSession.outputURL=[NSURL fileURLWithPath:filePath]；//输出路径
exportSession.outputFileType=AVFileTypeAppleM4A；//输出文件类型
exportSession.timeRange=exportTimeRange；//修剪时间范围
//exportSession.audioMix=exportAudioMix；//淡入音频混合
//执行导出
[exportSession exportAsynchronouslyWithCompletionHandler:^{
if（AVAssetExportSessionStatusCompleted==exportSession.status）{
NSLog（“AVAssetExportSessionStatusCompleted”）；
}else if（AVAssetExportSessionStatusFailed==exportSession.status）{
//由于您无法控制的事件，可能会发生故障
//例如，一个像电话一样的中断即将到来
//确保并妥善处理此案例
NSLog（@“AVAssetExportSessionStatusFailed”）；
}否则{
NSLog（@“导出会话状态：%ld”，（长）exportSession.Status）；
}
}];
返回YES；}

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谢谢

有关详细信息：

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但这种方法只允许声音以m4a格式保存，如果您想修剪mp3或caf文件并保持格式，该怎么办？修剪mp3也可以工作，输出以m4a格式存储2年后，您仍然可以救我的命：）如果有人在swift 4中查找答案，请查看以下链接：

- (BOOL)exportAssettoFilePath:(NSString *)filePath {


NSString *inputFilePath = <inputFilePath>;

NSURL *videoToTrimURL = [NSURL fileURLWithPath:inputFilePath];
AVAsset *avAsset = [AVAsset assetWithURL:videoToTrimURL];

// 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: %ld", (long)exportSession.status);
    }
}];

return YES;}