Iphone 使用淡入淡出功能保存音频，设置VolumerampfromStartVolume在iOS中不工作

我正在尝试为一个iPhone项目剪切一个音频文件。我可以剪切并保存它，但是我尝试应用的任何淡入/淡出都不起作用，音频文件只是被剪切保存而不是淡出

我正在使用以下代码：

//
// NO PROBLEMS TO SEE HERE, MOVE ON
//
    NSArray *documentsFolders = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    int currentFileNum = 10;
    NSURL *url = [NSURL fileURLWithPath: [[documentsFolders objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@%d.%@", AUDIO_SOURCE_FILE_NAME ,currentFileNum, AUDIO_SOURCE_FILE_EXTENSION ]]];
    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES]
                                                        forKey:AVURLAssetPreferPreciseDurationAndTimingKey];
    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:url options:options];
    AVAssetExportSession* exporter = [AVAssetExportSession exportSessionWithAsset:asset presetName:AVAssetExportPresetAppleM4A];

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

    NSString* outPath = [[documentsFolders objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@%d.%@", AUDIO_CUTTED_FILE_NAME ,currentFileNum, AUDIO_SOURCE_FILE_EXTENSION ]];

    NSURL* const outUrl = [NSURL fileURLWithPath:outPath];
    exporter.outputURL = outUrl;

    float endTrimTime = CMTimeGetSeconds(asset.duration);
    float startTrimTime = fminf(AUDIO_DURATION, endTrimTime);
    CMTime startTrimCMTime=CMTimeSubtract(asset.duration, CMTimeMake(startTrimTime, 1));
    exporter.timeRange = CMTimeRangeMake(startTrimCMTime, asset.duration);

//
// TRYING TO APPLY FADEIN FADEOUT, NOT WORKING, NO RESULTS, "CODE IGNORED"
//
    AVMutableAudioMix *exportAudioMix = [AVMutableAudioMix audioMix];

    NSMutableArray* inputParameters = [NSMutableArray arrayWithCapacity:1];

    CMTime startFadeInTime = startTrimCMTime;
    CMTime endFadeInTime = CMTimeMake(startTrimTime+1, 1);
    CMTime startFadeOutTime = CMTimeMake(endTrimTime-1, 1);
    CMTime endFadeOutTime = CMTimeMake(endTrimTime, 1);

    CMTimeRange fadeInTimeRange = CMTimeRangeFromTimeToTime(startFadeInTime, endFadeInTime);

    CMTimeRange fadeOutTimeRange = CMTimeRangeFromTimeToTime(startFadeOutTime, endFadeOutTime);

    AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParameters];
    [exportAudioMixInputParameters setVolume:0.0 atTime:CMTimeMakeWithSeconds(startTrimTime-0.01, 1)];
    [exportAudioMixInputParameters setVolumeRampFromStartVolume:0.0 toEndVolume:1.0 timeRange:fadeInTimeRange];
    [exportAudioMixInputParameters setVolumeRampFromStartVolume:1.0 toEndVolume:0.0 timeRange:fadeOutTimeRange];

    [inputParameters insertObject:exportAudioMixInputParameters atIndex:0];

    exportAudioMix.inputParameters = inputParameters;
    exporter.audioMix = exportAudioMix;

    [exporter exportAsynchronouslyWithCompletionHandler:^(void) {
        NSString* message;
        switch (exporter.status) {
            case AVAssetExportSessionStatusFailed:
                message = [NSString stringWithFormat:@"Export failed. Error: %@", exporter.error.description];
                [asset release];
                break;
            case AVAssetExportSessionStatusCompleted: {
                [asset release];
                [self reallyConvert:currentFileNum];
                message = [NSString stringWithFormat:@"Export completed: %@", outPath];
                break;
            }
            case AVAssetExportSessionStatusCancelled:
                message = [NSString stringWithFormat:@"Export cancelled!"];
                [asset release];
                break;
            default:
                NSLog(@"Export 4 unhandled status: %d", exporter.status);
                [asset release];
                break;
        }       
    }];

---

您需要选择轨迹。而不是打电话：

AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParameters];

电话：

在现有代码中，还可以指定如下轨迹：

exportAudioMixInputParameters.trackID = [[[asset tracksWithMediaType:AVMediaTypeAudio]objectAtIndex:0] trackID];

祝你好运

这是解决方案

setVolumeRampFromStartVolume不起作用

AVMutableAudioMix *exportAudioMix = [AVMutableAudioMix audioMix];
AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:track];

//淡入

[exportAudioMixInputParameters setVolume:0.0 atTime:CMTimeMakeWithSeconds(start-1, 1)];
[exportAudioMixInputParameters setVolume:0.1 atTime:CMTimeMakeWithSeconds(start, 1)];
[exportAudioMixInputParameters setVolume:0.5 atTime:CMTimeMakeWithSeconds(start+1, 1)];
[exportAudioMixInputParameters setVolume:1.0 atTime:CMTimeMakeWithSeconds(start+2, 1)];

//淡出

[exportAudioMixInputParameters setVolume:1.0 atTime:CMTimeMakeWithSeconds((start+length-2), 1)];
[exportAudioMixInputParameters setVolume:0.5 atTime:CMTimeMakeWithSeconds((start+length-1), 1)];
[exportAudioMixInputParameters setVolume:0.1 atTime:CMTimeMakeWithSeconds((start+length), 1)];

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 ranges
exportSession.audioMix = exportAudioMix; // fade in audio mix
// perform the export
[exportSession exportAsynchronouslyWithCompletionHandler:^{

    if (AVAssetExportSessionStatusCompleted == exportSession.status) {
        NSLog(@"AVAssetExportSessionStatusCompleted");

    } else if (AVAssetExportSessionStatusFailed == exportSession.status) {
        NSLog(@"AVAssetExportSessionStatusFailed");

    } else {
        NSLog(@"Export Session Status: %d", exportSession.status);
    }
}];

---

这是我的工作代码，拿着它，祝你有愉快的一天

+(void)makeAudioFadeOutWithSourceURL:(NSURL*)sourceURL destinationURL:(NSURL*)destinationURL fadeOutBeginSecond:(NSInteger)beginTime fadeOutEndSecond:(NSInteger)endTime fadeOutBeginVolume:(CGFloat)beginVolume fadeOutEndVolume:(CGFloat)endVolume callback:(void(^)(BOOL))callback
{
    NSAssert(callback, @"need callback");
    NSParameterAssert(beginVolume >= 0 && beginVolume <=1);
    NSParameterAssert(endVolume >= 0 && endVolume <= 1);

    BOOL sourceExist = [[NSFileManager defaultManager] fileExistsAtPath:sourceURL.path];
    NSAssert(sourceExist, @"source not exist");

    AVURLAsset *asset = [AVAsset assetWithURL:sourceURL];;

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

    exporter.outputURL = destinationURL;
    exporter.outputFileType = AVFileTypeAppleM4A;

    AVMutableAudioMix *exportAudioMix = [AVMutableAudioMix audioMix];

    AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:asset.tracks.lastObject];
    [exportAudioMixInputParameters setVolumeRampFromStartVolume:beginVolume toEndVolume:endVolume timeRange:CMTimeRangeMake(CMTimeMakeWithSeconds(beginTime, 1), CMTimeSubtract(CMTimeMakeWithSeconds(endTime, 1), CMTimeMakeWithSeconds(beginTime, 1)))];
    NSArray *audioMixParameters = @[exportAudioMixInputParameters];
    exportAudioMix.inputParameters = audioMixParameters;

    exporter.audioMix = exportAudioMix;

    [exporter exportAsynchronouslyWithCompletionHandler:^(void){
        AVAssetExportSessionStatus status = exporter.status;
        if (status != AVAssetExportSessionStatusCompleted) {
            if (callback) {
                callback(NO);
            }
        }
        else {
            if (callback) {
                callback(YES);
            }
        }
        NSError *error = exporter.error;
        NSLog(@"export done,error %@,status %d",error,status);
    }];
}

+（void）makeAudioFadeOutWithSourceURL:（NSURL*）sourceURL destinationURL:（NSURL*）destinationURL fadeOutBeginSecond:（NSInteger）beginTime FadeOutSecond:（NSInteger）endTime fadeOutBeginVolume:（CGFloat）beginVolume FadeOutVolume:（CGFloat）endVolume回调:（void（^）（BOOL））回调
{
NSAssert（回调，@“需要回调”）；
NSParameterAssert（beginVolume>=0&&beginVolume=0&&endVolume我犯了几十次与您相同的错误！
苹果的API在这方面真的很奇怪：

CMTimeRange fadeInTimeRange = CMTimeRangeFromTimeToTime(startFadeInTime, endFadeInTime);

CMTimeRange fadeOutTimeRange = CMTimeRangeFromTimeToTime(startFadeOutTime, endFadeOutTime);

应该是：

CMTimeRangeFromTimeToTime(startFadeInTime, fadeInDURATION);

CMTimeRangeFromTimeToTime(startFadeOutTime, fadeOutDURATION);

CMTimeRange是从开始和持续时间创建的，而不是从开始和结束

但大多数情况下，结束时间也是持续时间（如果开始时间为0），这就是为什么这么多人（包括我）会犯错误

没有苹果，这一点都不直观！
你找到任何解决方案了吗？请帮助。这是大多数人犯的错误，因此看不到setVolumeRampFromStartVolume起作用。（这是我迄今为止的经验）。不要做：CMTimeRangeMake（开始时间，结束时间），而是做：CMTimeRangeMake（开始时间，范围持续时间）我犯过几十次这样的错误，因为如果你的持续时间从0开始，范围持续时间=结束时间，但在淡出的情况下，它不是！
CMTimeRangeFromTimeToTime(startFadeInTime, fadeInDURATION);

CMTimeRangeFromTimeToTime(startFadeOutTime, fadeOutDURATION);