Swift: How to Delete Part of Audio

swift: how to delete part of audio?

CMTimeRangeGetUnion returns another CMTimeRange, which is just a (start-)time and a duration. So there is nothing than can hold the two time ranges required to do what you are expecting. In extension, AVAssetExportSession has no API that takes a list of time ranges to export.

But there is a way to accomplish it. The idea is to create an editable copy of the asset, delete the time range, and then export the editable copy. AVMutableComposition does this:

// assuming 'asset', 'endTimeOfRange1' and 'startTimeOfRange2' from the question:

// create empty mutable composition
let composition: AVMutableComposition = AVMutableComposition()
// copy all of original asset into the mutable composition, effectively creating an editable copy
try composition.insertTimeRange( CMTimeRangeMake( kCMTimeZero, asset.duration), of: asset, at: kCMTimeZero)

// now edit as required, e.g. delete a time range
let startTime = CMTime(seconds: endTimeOfRange1, preferredTimescale: 100)
let endTime = CMTime(seconds: startTimeOfRange2, preferredTimescale: 100)
composition.removeTimeRange( CMTimeRangeFromTimeToTime( startTime, endTime))

// since AVMutableComposition is an AVAsset subclass, it can be exported with AVAssetExportSession (or played with an AVPlayer(Item))
if let exporter = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetAppleM4A) 
{
    // configure session and exportAsynchronously as above. 
    // You don't have to set the timeRange of the exportSession
}

Note that copying from the asset to the composition only modifies some in-memory structures defining which samples go where on the time line, but doesn't actually moves any media samples around. This is not done until exporting; as result, editing is (relatively) fast, and you have to keep the source file around at least until export is finished.

Swift - Remove audio from video

with the help of this link I wrote this code & this worked for me...

var mutableVideoURL = NSURL() //final video url
func removeAudioFromVideo(_ videoURL: URL) {
        let inputVideoURL: URL = videoURL
        let sourceAsset = AVURLAsset(url: inputVideoURL)
        let sourceVideoTrack: AVAssetTrack? = sourceAsset.tracks(withMediaType: AVMediaTypeVideo)[0]
        let composition : AVMutableComposition = AVMutableComposition()
        let compositionVideoTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
        let x: CMTimeRange = CMTimeRangeMake(kCMTimeZero, sourceAsset.duration)
        _ = try? compositionVideoTrack!.insertTimeRange(x, of: sourceVideoTrack!, at: kCMTimeZero)
        mutableVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/FinalVideo.mp4")
        let exporter: AVAssetExportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.outputURL = mutableVideoURL as URL
        removeFileAtURLIfExists(url: mutableVideoURL)
        exporter.exportAsynchronously(completionHandler:
            {
                switch exporter.status
                {
                    case AVAssetExportSessionStatus.failed:
                        print("failed \(exporter.error)")
                    case AVAssetExportSessionStatus.cancelled:
                        print("cancelled \(exporter.error)")
                    case AVAssetExportSessionStatus.unknown:
                        print("unknown\(exporter.error)")
                    case AVAssetExportSessionStatus.waiting:
                        print("waiting\(exporter.error)")
                    case AVAssetExportSessionStatus.exporting:
                        print("exporting\(exporter.error)")
                    default:
                        print("-----Mutable video exportation complete.")
                }
            })
    }

    func removeFileAtURLIfExists(url: NSURL) {
        if let filePath = url.path {
            let fileManager = FileManager.default
            if fileManager.fileExists(atPath: filePath) {
                do{
                    try fileManager.removeItem(atPath: filePath)
                } catch let error as NSError {
                    print("Couldn't remove existing destination file: \(error)")
                }
            }
        }
    }

iOS Audio Trimming

Here's the code that I've used to trim audio from a pre-existing file. You'll need to change the M4A related constants if you've saved or are saving to another format.

- (BOOL)trimAudio
{
    float vocalStartMarker = <starting time>;
    float vocalEndMarker = <ending time>;

    NSURL *audioFileInput = <your pre-existing file>;
    NSURL *audioFileOutput = <the file you want to create>;

    if (!audioFileInput || !audioFileOutput)
    {
        return NO;
    }

    [[NSFileManager defaultManager] removeItemAtURL:audioFileOutput error:NULL];
    AVAsset *asset = [AVAsset assetWithURL:audioFileInput];

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

    if (exportSession == nil)
    {        
        return NO;
    }

    CMTime startTime = CMTimeMake((int)(floor(vocalStartMarker * 100)), 100);
    CMTime stopTime = CMTimeMake((int)(ceil(vocalEndMarker * 100)), 100);
    CMTimeRange exportTimeRange = CMTimeRangeFromTimeToTime(startTime, stopTime);

    exportSession.outputURL = audioFileOutput;
    exportSession.outputFileType = AVFileTypeAppleM4A;
    exportSession.timeRange = exportTimeRange;

    [exportSession exportAsynchronouslyWithCompletionHandler:^
     {
         if (AVAssetExportSessionStatusCompleted == exportSession.status)
         {
             // It worked!
         } 
         else if (AVAssetExportSessionStatusFailed == exportSession.status)
         {
             // It failed...
         }
     }];

    return YES;
}

There's also Technical Q&A 1730, which gives a slightly more detailed approach.

How to trim audio data?

You are taking compressed audio (M4A) and uncompressing it, which is what you need to do to trim down the audio content. If you want to get back to the 2.5 MB range, you will need to recompress your audio when done.

Keep in mind that repeated lossy uncompress-edit-recompress cycles will degrade the quality of your audio. If you are going to be performing a lot of audio edit operations, you should transform your audio from compressed to uncompressed, then run your transforms, and finally recompress at the end.

Audio cutter native iOS element

UI element for audio wave - https://stackoverflow.com/a/64709493/13296047. This post answers exactly how to create a audio wave from recorded audio.

UI element for cutting an audio wave - https://stackoverflow.com/a/52062837/13296047

UI element in the bottom for audio cutting feature - https://stackoverflow.com/a/40670853/13296047

This is a very good Voice Memos clone you can use for reference: https://github.com/HassanElDesouky/VoiceMemosClone

Remove all files from within documentDirectory in Swift

First of all the error occurs because the signature of the API is wrong. It's just removeItem(at:) without the other parameters.

A second issue is that you are going to delete the Documents directory itself rather than the files in the directory which you are discouraged from doing that.

You have to get the contents of the directory and add a check for example to delete only MP3 files. A better solution would be to use a subfolder.

let documentsUrl =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

do {
    let fileURLs = try FileManager.default.contentsOfDirectory(at: documentsUrl,
                                                               includingPropertiesForKeys: nil,
                                                               options: .skipsHiddenFiles)
    for fileURL in fileURLs where fileURL.pathExtension == "mp3" {
        try FileManager.default.removeItem(at: fileURL)   
    }
} catch  { print(error) }

Side note: It is highly recommended to use always the URL related API of FileManager.

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