Сохраняйте звук с постепенным исчезновением с setVolumeRampFromStartVolume, не работающим в iOS

Question

Я пытаюсь вырезать аудиофайл для проекта iPhone. Я могу обрезать его и сохранить, но любое исчезновение / исчезновение, которое я пытаюсь применить, не работает, аудиофайл просто сохраняется вырезанным, но не выцветшим.

Я использую следующий код:

//
// 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;
        }       
    }];

Answer 1

Я совершил ту же ошибку, что и вы, десятки раз! API от Apple действительно странный в этом:

CMTimeRange fadeInTimeRange = CMTimeRangeFromTimeToTime(startFadeInTime, endFadeInTime);

CMTimeRange fadeOutTimeRange = CMTimeRangeFromTimeToTime(startFadeOutTime, endFadeOutTime);

Должно быть:

CMTimeRangeFromTimeToTime(startFadeInTime, fadeInDURATION);

CMTimeRangeFromTimeToTime(startFadeOutTime, fadeOutDURATION);

CMTimeRange создается из начала и продолжительности, а не из начала и конца!

Но в большинстве случаев время окончания также является продолжительностью (если время начала равно 0), поэтому многие люди (включая меня) допускают ошибку.

И нет Apple, это совсем не интуитивно понятно!

Answer 2

Вот решение.

setVolumeRampFromStartVolume не работает.

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

// исчезновение

[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)];

// исчезновение

[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);
    }
}];

Answer 3

Вам нужно выбрать трек. Вместо звонка:

AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParameters];

Звоните:

AVAssetTrack *assetTrack = [[asset tracksWithMediaType:AVMediaTypeAudio]objectAtIndex:0];

AVMutableAudioMixInputParameters *exportAudioMixInputParameters = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:assetTrack];

В вашем существующем коде вы также можете указать трек следующим образом:

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

Удачи!

Answer 4

Это мой рабочий код, просто возьми его и хорошего дня!

+(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);
    }];
}