How to do Slow Motion video in IOS
Solution 1:
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)
Solution 2:
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)
Solution 3:
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.");
}
}
Solution 4:
I would extract all frames from initial video using ffmpeg and then collect together using AVAssetWriter but with lower frame rate. For getting more fulid slow motion maybe you will need to apply some blur effect, or even generate frame between existing, which will be mix from two frames.
Solution 5:
An example in swift :
I
var asset: AVAsset?
func configureAssets(){
let videoAsset = AVURLAsset(url: Bundle.main.url(forResource: "sample", withExtension: "m4v")!)
let audioAsset = AVURLAsset(url: Bundle.main.url(forResource: "sample", withExtension: "m4a")!)
// let audioAsset2 = AVURLAsset(url: Bundle.main.url(forResource: "audio2", withExtension: "m4a")!)
let comp = AVMutableComposition()
let videoAssetSourceTrack = videoAsset.tracks(withMediaType: AVMediaTypeVideo).first! as AVAssetTrack
let audioAssetSourceTrack = videoAsset.tracks(withMediaType: AVMediaTypeAudio).first! as AVAssetTrack
// let audioAssetSourceTrack2 = audioAsset2.tracks(withMediaType: AVMediaTypeAudio).first! as AVAssetTrack
let videoCompositionTrack = comp.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
let audioCompositionTrack = comp.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)
do {
try videoCompositionTrack.insertTimeRange(
CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(9 , 600)),
of: videoAssetSourceTrack,
at: kCMTimeZero)
try audioCompositionTrack.insertTimeRange(
CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(9, 600)),
of: audioAssetSourceTrack,
at: kCMTimeZero)
//
// try audioCompositionTrack.insertTimeRange(
// CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(3, 600)),
// of: audioAssetSourceTrack2,
// at: CMTimeMakeWithSeconds(7, 600))
let videoScaleFactor = Int64(2.0)
let videoDuration: CMTime = videoAsset.duration
videoCompositionTrack.scaleTimeRange(CMTimeRangeMake(kCMTimeZero, videoDuration), toDuration: CMTimeMake(videoDuration.value * videoScaleFactor, videoDuration.timescale))
audioCompositionTrack.scaleTimeRange(CMTimeRangeMake(kCMTimeZero, videoDuration), toDuration: CMTimeMake(videoDuration.value * videoScaleFactor, videoDuration.timescale))
videoCompositionTrack.preferredTransform = videoAssetSourceTrack.preferredTransform
}catch { print(error) }
asset = comp
}
II
func createFileFromAsset(_ asset: AVAsset){
let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0] as URL
let filePath = documentsDirectory.appendingPathComponent("rendered-audio.m4v")
deleteFile(filePath)
if let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetLowQuality){
exportSession.canPerformMultiplePassesOverSourceMediaData = true
exportSession.outputURL = filePath
exportSession.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)
exportSession.outputFileType = AVFileTypeQuickTimeMovie
exportSession.exportAsynchronously {
_ in
print("finished: \(filePath) : \(exportSession.status.rawValue) ")
}
}
}
func deleteFile(_ filePath:URL) {
guard FileManager.default.fileExists(atPath: filePath.path) else {
return
}
do {
try FileManager.default.removeItem(atPath: filePath.path)
}catch{
fatalError("Unable to delete file: \(error) : \(#function).")
}
}