How to do Slow Motion video in IOS
Slower + Faster with or without audio track
I have tried and able to Slower the asset.
compositionVideoTrack?.scaleTimeRange(timeRange, toDuration: scaledVideoDuration) did the trick.
I made a class which will help you to generate a slower video from AVAsset.
+ point is you can also make it faster and another + point is it will handle the audio too.
Here is my custom class sample:
import UIKit
import AVFoundation
enum SpeedoMode {
case Slower
case Faster
}
class VSVideoSpeeder: NSObject {
/// Singleton instance of `VSVideoSpeeder`
static var shared: VSVideoSpeeder = {
return VSVideoSpeeder()
}()
/// Range is b/w 1x, 2x and 3x. Will not happen anything if scale is out of range. Exporter will be nil in case url is invalid or unable to make asset instance.
func scaleAsset(fromURL url: URL, by scale: Int64, withMode mode: SpeedoMode, completion: @escaping (_ exporter: AVAssetExportSession?) -> Void) {
/// Check the valid scale
if scale < 1 || scale > 3 {
/// Can not proceed, Invalid range
completion(nil)
return
}
/// Asset
let asset = AVAsset(url: url)
/// Video Tracks
let videoTracks = asset.tracks(withMediaType: AVMediaType.video)
if videoTracks.count == 0 {
/// Can not find any video track
completion(nil)
return
}
/// Get the scaled video duration
let scaledVideoDuration = (mode == .Faster) ? CMTimeMake(asset.duration.value / scale, asset.duration.timescale) : CMTimeMake(asset.duration.value * scale, asset.duration.timescale)
let timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)
/// Video track
let videoTrack = videoTracks.first!
let mixComposition = AVMutableComposition()
let compositionVideoTrack = mixComposition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)
/// Audio Tracks
let audioTracks = asset.tracks(withMediaType: AVMediaType.audio)
if audioTracks.count > 0 {
/// Use audio if video contains the audio track
let compositionAudioTrack = mixComposition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)
/// Audio track
let audioTrack = audioTracks.first!
do {
try compositionAudioTrack?.insertTimeRange(timeRange, of: audioTrack, at: kCMTimeZero)
compositionAudioTrack?.scaleTimeRange(timeRange, toDuration: scaledVideoDuration)
} catch _ {
/// Ignore audio error
}
}
do {
try compositionVideoTrack?.insertTimeRange(timeRange, of: videoTrack, at: kCMTimeZero)
compositionVideoTrack?.scaleTimeRange(timeRange, toDuration: scaledVideoDuration)
/// Keep original transformation
compositionVideoTrack?.preferredTransform = videoTrack.preferredTransform
/// Initialize Exporter now
let outputFileURL = URL(fileURLWithPath: "/Users/thetiger/Desktop/scaledVideo.mov")
/// Note:- Please use directory path if you are testing with device.
if FileManager.default.fileExists(atPath: outputFileURL.absoluteString) {
try FileManager.default.removeItem(at: outputFileURL)
}
let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)
exporter?.outputURL = outputFileURL
exporter?.outputFileType = AVFileType.mov
exporter?.shouldOptimizeForNetworkUse = true
exporter?.exportAsynchronously(completionHandler: {
completion(exporter)
})
} catch let error {
print(error.localizedDescription)
completion(nil)
return
}
}
}
I took 1x, 2x and 3x as a valid scale. Class contains the proper validation and handling. Below is the sample of how to use this function.
let url = Bundle.main.url(forResource: "1", withExtension: "mp4")!
VSVideoSpeeder.shared.scaleAsset(fromURL: url, by: 3, withMode: SpeedoMode.Slower) { (exporter) in
if let exporter = exporter {
switch exporter.status {
case .failed: do {
print(exporter.error?.localizedDescription ?? "Error in exporting..")
}
case .completed: do {
print("Scaled video has been generated successfully!")
}
case .unknown: break
case .waiting: break
case .exporting: break
case .cancelled: break
}
}
else {
/// Error
print("Exporter is not initialized.")
}
}
This line will handle the audio scaling
compositionAudioTrack?.scaleTimeRange(timeRange, toDuration: scaledVideoDuration)
I have achieved on adding slow motion to video including audio as well with proper output orientation.
- (void)SlowMotion:(NSURL *)URl
{
AVURLAsset* videoAsset = [AVURLAsset URLAssetWithURL:URl options:nil]; //self.inputAsset;
AVAsset *currentAsset = [AVAsset assetWithURL:URl];
AVAssetTrack *vdoTrack = [[currentAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
//create mutable composition
AVMutableComposition *mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
NSError *videoInsertError = nil;
BOOL videoInsertResult = [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
atTime:kCMTimeZero
error:&videoInsertError];
if (!videoInsertResult || nil != videoInsertError) {
//handle error
return;
}
NSError *audioInsertError =nil;
BOOL audioInsertResult =[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:[[currentAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
atTime:kCMTimeZero
error:&audioInsertError];
if (!audioInsertResult || nil != audioInsertError) {
//handle error
return;
}
CMTime duration =kCMTimeZero;
duration=CMTimeAdd(duration, currentAsset.duration);
//slow down whole video by 2.0
double videoScaleFactor = 2.0;
CMTime videoDuration = videoAsset.duration;
[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, videoDuration)
toDuration:CMTimeMake(videoDuration.value*videoScaleFactor, videoDuration.timescale)];
[compositionAudioTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, videoDuration)
toDuration:CMTimeMake(videoDuration.value*videoScaleFactor, videoDuration.timescale)];
[compositionVideoTrack setPreferredTransform:vdoTrack.preferredTransform];
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSString *outputFilePath = [docsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"slowMotion.mov"]];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
[[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];
NSURL *_filePath = [NSURL fileURLWithPath:outputFilePath];
//export
AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition
presetName:AVAssetExportPresetLowQuality];
assetExport.outputURL=_filePath;
assetExport.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;
[assetExport exportAsynchronouslyWithCompletionHandler:^
{
switch ([assetExport status]) {
case AVAssetExportSessionStatusFailed:
{
NSLog(@"Export session faiied with error: %@", [assetExport error]);
dispatch_async(dispatch_get_main_queue(), ^{
// completion(nil);
});
}
break;
case AVAssetExportSessionStatusCompleted:
{
NSLog(@"Successful");
NSURL *outputURL = assetExport.outputURL;
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputURL]) {
[self writeExportedVideoToAssetsLibrary:outputURL];
}
dispatch_async(dispatch_get_main_queue(), ^{
// completion(_filePath);
});
}
break;
default:
break;
}
}];
}
- (void)writeExportedVideoToAssetsLibrary :(NSURL *)url {
NSURL *exportURL = url;
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:exportURL]) {
[library writeVideoAtPathToSavedPhotosAlbum:exportURL completionBlock:^(NSURL *assetURL, NSError *error){
dispatch_async(dispatch_get_main_queue(), ^{
if (error) {
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:[error localizedDescription]
message:[error localizedRecoverySuggestion]
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[alertView show];
}
if(!error)
{
// [activityView setHidden:YES];
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Sucess"
message:@"video added to gallery successfully"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[alertView show];
}
#if !TARGET_IPHONE_SIMULATOR
[[NSFileManager defaultManager] removeItemAtURL:exportURL error:nil];
#endif
});
}];
} else {
NSLog(@"Video could not be exported to assets library.");
}
}
You could scale video using AVFoundation and CoreMedia frameworks. Take a look at the AVMutableCompositionTrack method:
- (void)scaleTimeRange:(CMTimeRange)timeRange toDuration:(CMTime)duration;
Sample:
AVURLAsset* videoAsset = nil; //self.inputAsset;
//create mutable composition
AVMutableComposition *mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
NSError *videoInsertError = nil;
BOOL videoInsertResult = [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
atTime:kCMTimeZero
error:&videoInsertError];
if (!videoInsertResult || nil != videoInsertError) {
//handle error
return;
}
//slow down whole video by 2.0
double videoScaleFactor = 2.0;
CMTime videoDuration = videoAsset.duration;
[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, videoDuration)
toDuration:CMTimeMake(videoDuration.value*videoScaleFactor, videoDuration.timescale)];
//export
AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition
presetName:AVAssetExportPresetLowQuality];
(Probably audio track from videoAsset should also be added to mixComposition)