简介
首先我们需要了解在使用LivePhoto是会有这样的效果,我们点击拍照键,系统会为我们展示一段视频和一张封面图。
如果只是视频和图片我们可简单地将其合称为一段LivePhoto,但是最难实现的效果就是,系统为我们展示的3秒视频,前面1.5秒是在你按拍照键之前的。基于这一点我们要实现预录制的功能。
实现方案
要实现这一效果,我们通常会想到,在我点击实况按钮或者进入我的相机App的时候就开始录制视频,点击拍照键后1.5秒就结束录制,最终裁剪最后的三秒。这么做也未尝不可,但是带来是后果是如果在live页面停留太久,低内存的机器的缓冲区会满,造成崩溃。
我在stackoverflow上提问后,有人告诉我,可以维护一个缓冲区,缓冲区内只保存最近的1.5s视频,拍摄完成再进行拼接。
那么问题来了,缓冲区该如何设计呢?怎么才能实现只保存最近1.5秒这一效果呢?
1.设置缓存队列
我经过思考,认为,维护一个视频队列是最合适的,也是较容易去实现的。
我在用户点击实况按钮时,开始录制,但是所不同的是,我会设置一个计时器,每过1.5秒就停止录制,存到缓存区队列,然后继续录制。如果队列的长度超过2,那么就把队首的一段视频删除。
这样就保证了缓冲区一定存在我拍照前1.5秒的视频,也不会造成缓存区满的状况。
2.点击拍照键的操作
用户点击拍照键时,立即停止录制,保存,然后开始录制1.5秒的视频。这样就有了后面两段视频。
我简单的画了个示意图:
字丑,凑合着看:
IMG_20180904_144636.jpg
也就是说,我点击拍照键的一瞬间,肯定不是恰好的1.5秒视频录制结束的时候,比如是0.6秒,那么我把这三段视频保存,三段视频即可合成一段LivePhoto。
所以,核心思想就是用队列保存三段视频,最后只对这三段视频进行裁切合并。
3.具体实现代码
这里给出部分代码。项目来自于AppStore上线项目#折纸相机#,希望大家多多支持。
最新版本尚未更新预录制livephoto功能。
变量定义
//判断是否正在拍摄livePhoto
var isLivePhoto = false
//第一段计时器
var liveTimer:Timer?
//第二段计时器
var liveTimer2:Timer?
var liveCounter:Double = 0.5;
var liveCounter2:Double = 0.5;
var liveUrl:URL!
var videoUrls = [URL]()
var saveManager:SaveVieoManager?
具体核心代码
func setLiveMode(){
if !isLivePhoto{
isLivePhoto = true
setLiveStart()
}else{
isLivePhoto = false
movieWriter?.finishRecording()
liveTimer?.invalidate()
liveTimer = nil
}
}
/// 开始录制LivePhoto
func setLiveStart(){
//shotButton.isUserInteractionEnabled = false
startRecord()
videoUrls.append(videoUrl!)
self.topView.liveCounter.isHidden = false
topView.setCounter(text: "0")
liveTimer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(updateLiveCounter), userInfo: nil, repeats: true)
// liveTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateLiveCounter), userInfo: nil, repeats: true)
}
//倒计时控制
@objc func updateLiveCounter(){
liveCounter = liveCounter + 0.5
print("正在拍摄LivePhoto: ",liveCounter)
topView.setCounter(text: "\(liveCounter)")
// if liveCounter == 3{
// finishLiveRecord()
// }
if liveCounter == 1.5{
movieWriter?.finishRecording()
deleteLiveBuffer()
startRecord()
videoUrls.append(videoUrl!)
liveCounter = 0
}
}
/// 倒计时结束,结束录制
func finishLiveRecord(){
movieWriter?.finishRecording()
shotButton.isUserInteractionEnabled = false
liveTimer?.invalidate()
startRecord()
liveCounter2 = 0
liveTimer2 = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(setIntervalFinish), userInfo: nil, repeats: true)
}
//录制完成,进行合成和跳转
@objc func setIntervalFinish(){
liveCounter2 = liveCounter2 + 0.5
if liveCounter2 == 1.5{
deleteAdditionalBuffer()
shotButton.isUserInteractionEnabled = false
movieWriter?.failureBlock = {
Error in
print(Error as Any)
}
// movieWriter?.completionBlock = {
self.videoUrls.append(self.videoUrl!)
self.movieWriter?.finishRecording()
print("-------------:",self.videoUrls)
self.topView.liveCounter.isHidden = true
self.shotButton.isUserInteractionEnabled = true
self.liveTimer = nil
self.liveTimer2?.invalidate()
self.liveTimer2 = nil
self.liveCounter2 = 0
setLiveStart()
//视频合成
// ProgressHUD.show("合成中")
saveManager = SaveVieoManager(urls: videoUrls)
let newUrl = URL(fileURLWithPath: "\(NSTemporaryDirectory())folder_all.mp4")
unlink(newUrl.path)
videoUrl = newUrl
//视频裁剪以及合成
saveManager?.combineLiveVideos(success: {
com in
self.saveManager?.store(com, storeUrl: newUrl, success:{
DispatchQueue.main.async {
let vc = CheckViewController.init(image: nil, type: 2)
vc.videoUrl = newUrl
weak var weakSelf = self
vc.videoScale = weakSelf?.scaleRate
vc.willDismiss = {
//将美颜状态重置
if (weakSelf?.isBeauty)!{
weakSelf?.isBeauty = false
weakSelf?.defaultBottomView.beautyButton.isSelected = false
}
//使用闭包,在vc返回时将底部隐藏,点击切换时在取消隐藏
if weakSelf?.scaleRate != 0{
// weakSelf?.scaleRate = 0
weakSelf?.defaultBottomView.backgroundColor = UIColor.clear
}
//LivePhoto录像状态重置
}
// ProgressHUD.showSuccess("合成成功")
// weakSelf?.videoUrls.removeAll()
weakSelf?.present(vc, animated: true, completion: nil)
//self.setLiveStart()
}
})
})
}
}
func deleteLiveBuffer(){
if videoUrls.count>=2{
do {
try FileManager.default.removeItem(atPath: (videoUrls.first!.path))
videoUrls.removeFirst()
} catch {
}
}
}
func deleteAdditionalBuffer(){
while videoUrls.count>=3{
do {
try FileManager.default.removeItem(atPath: (videoUrls.first!.path))
videoUrls.removeFirst()
} catch {
}
}
}
视频裁剪和合成部分代码:
裁剪视频
/// 剪辑视频
///
/// - Parameters:
/// - frontOffset: 前面剪几秒
/// - endOffset: 后面剪几秒
/// - index: url的下标
/// - Returns: 合成
func cutLiveVideo(frontOffset:Float64,endOffset:Float64,index:Int)->AVMutableComposition{
let composition = AVMutableComposition()
// Create the video composition track.
let compositionVideoTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)
// Create the audio composition track.
let compositionAudioTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
let pathUrl = videoUrls[index]
let asset = AVURLAsset(url: pathUrl, options: nil)
let videoTrack: AVAssetTrack = asset.tracks(withMediaType: .video)[0]
let audioTrack: AVAssetTrack = asset.tracks(withMediaType: .audio)[0]
compositionVideoTrack?.preferredTransform = videoTrack.preferredTransform
// CMTime
let trackDuration: CMTime = videoTrack.timeRange.duration
let trackTimescale: CMTimeScale = trackDuration.timescale
// 用timescale构造前后截取位置的CMTime
let startTime: CMTime = CMTimeMakeWithSeconds(frontOffset, trackTimescale)
let endTime: CMTime = CMTimeMakeWithSeconds(endOffset, trackTimescale)
let intendedDuration: CMTime = CMTimeSubtract(asset.duration, CMTimeAdd(startTime, endTime))
try? compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(startTime, intendedDuration), of: videoTrack, at: kCMTimeZero)
try? compositionAudioTrack?.insertTimeRange(CMTimeRangeMake(startTime, intendedDuration), of: audioTrack, at: kCMTimeZero)
return composition
}
合成视频
func combineLiveVideos(success:@escaping(_ mixComposition:AVMutableComposition)->()){
for i in 0...videoUrls.count-1{
//剪第一段
if i == 0{
//求liveVideo第二段长度n,需要用1.5 - 此长度作为第一段需要减去的长度
if videoUrls.count >= 1{
var videoAsset2:AVURLAsset?
videoAsset2 = AVURLAsset.init(url: videoUrls[1])
let tt = videoAsset2!.duration
let getLengthOfVideo2 = Double(tt.value)/Double(tt.timescale)
//减掉开始 n 秒
let video1Composition = cutLiveVideo(frontOffset: getLengthOfVideo2, endOffset: 0.0, index: 0)
let newUrl = URL(fileURLWithPath: "\(NSTemporaryDirectory())foldercut_1.mp4")
unlink(newUrl.path)
videoUrls[0] = newUrl
//裁剪完第一段视频后,开始进行三段视频的合成
store(video1Composition, storeUrl: newUrl, success: {
let mixCom = self.combineVideos()
success(mixCom)
})
}
}
}
}
存储视频
/**
* 存储合成的视频
*
* @param mixComposition mixComposition参数
* @param storeUrl 存储的路径
* @param successBlock successBlock
* @param failureBlcok failureBlcok
*/
func store(_ mixComposition:AVMutableComposition,storeUrl:URL,success successBlock:@escaping ()->()){
//weak var weakSelf = self
var assetExport: AVAssetExportSession? = nil
assetExport = AVAssetExportSession.init(asset: mixComposition, presetName: AVAssetExportPreset640x480)
assetExport?.outputFileType = AVFileType("com.apple.quicktime-movie")
assetExport?.outputURL = storeUrl
assetExport?.exportAsynchronously(completionHandler: {
successBlock()
// UISaveVideoAtPathToSavedPhotosAlbum((storeUrl.path), self,#selector(weakSelf?.saveVideo(videoPath:didFinishSavingWithError:contextInfo:)), nil)
})
}
好了,就到这里。
网友评论