使用AVMutableVideoComposition时AVMutableComposition冻结的奇怪行为 [英] Weird behaviour of AVMutableComposition freezing while using AVMutableVideoComposition
问题描述
我正在尝试使用 AVMutableComposition 合并多个视频。我遇到的问题是每当我尝试添加任何 AVMutableVideoComposition 来应用任何指令时，我的播放都会在 AVPlayer 中冻结准确的6秒持续时间。
另一个有趣的事情是，如果我在使用相同的 videoComposition导出后在iPad的照片应用中播放它，它会正常播放。那么为什么它会在6秒内在 AVPlayer 中冻结？
代码：
AVMutableComposition * mutableComposition = [AVMutableComposition composition];
AVMutableCompositionTrack * videoCompositionTrack = [mutableComposition addMutableTrackWithMediaType：AVMediaTypeVideo
preferredTrackID：kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack * audioCompositionTrack = [mutableComposition addMutableTrackWithMediaType：AVMediaTypeAudio
preferredTrackID：kCMPersistentTrackID_Invalid];
for（AVURLAsset *资产中的资产）
{
AVAssetTrack * assetTrack;
assetTrack = [[asset tracksWithMediaType：AVMediaTypeVideo] objectAtIndex：0];
AVAssetTrack * audioAssetTrack = [asset tracksWithMediaType：AVMediaTypeAudio] .firstObject;
NSError *错误;
[videoCompositionTrack insertTimeRange：CMTimeRangeMake（kCMTimeZero，assetTrack.timeRange.duration）
ofTrack：assetTrack
atTime：time
error：& error];
if（error）{
NSLog（@asset url ::％@，assetTrack.asset）;
NSLog（@Error1 - ％@，error.debugDescription）;
}
[audioCompositionTrack insertTimeRange：CMTimeRangeMake（kCMTimeZero，audioAssetTrack.timeRange.duration）
ofTrack：audioAssetTrack
atTime：time
error：& error ]。
if（error）{
NSLog（@Error2 - ％@，error.debugDescription）;
}
time = CMTimeAdd（time，assetTrack.timeRange.duration）;
if（CGSizeEqualToSize（size，CGSizeZero））{
size = assetTrack.naturalSize ;;
}
}
AVMutableVideoCompositionInstruction * mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
AVMutableVideoCompositionLayerInstruction * videoTrackLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack：videoCompositionTrack];
mainInstruction.timeRange = CMTimeRangeMake（kCMTimeZero，time）;
mainInstruction.layerInstructions = [NSArray arrayWithObjects：videoTrackLayerInstruction，nil];
AVMutableVideoComposition * mainCompositionInst = [AVMutableVideoComposition videoComposition];
mainCompositionInst.instructions = [NSArray arrayWithObject：mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake（1,30）;
mainCompositionInst.renderSize = size;
pi = [AVPlayerItem playerItemWithAsset：mutableComposition];
pi.videoComposition = mainCompositionInst;
此外，我知道问题主要是 videoComposition 因为如果我删除了 videoComposition ，那么它在 AVPlayer 上播放正常。
UPDATE 1 ：我刚发现它在6秒后冻结，如果我向后或向前拖动滑块（即使用 seekToTime ），它再次开始正常播放而不再进一步冻结。
即使视频被冻结，音频也能保持正常播放。
更新2 ：如果我继续使用 AVAssetExportSession 进行导出相同的 AVMutableComposition ，并从导出的视频加载资产，它工作正常。所以当我直接玩 AVMutableComposition 时，问题就出现了。
最后，我得到了解决这个问题的解决方案。
你应该在playerItem的状态改为.ReadyToPlay之后玩。
<请参见下文。
func startVideoPlayer（）{
let playerItem = AVPlayerItem（asset：self.composition ！）
playerItem.videoComposition = self.videoComposition！
让玩家= AVPlayer（playerItem：playerItem）
player.actionAtItemEnd = .None
videoPlayerLayer = AVPlayerLayer（玩家：玩家）
videoPlayerLayer！。 frame = self.bounds
/ * add playerItem的observer * /
player.addObserver（self，forKeyPath：player.currentItem.status，options：.New，context：nil）
NSNotificationCenter.defaultCenter（）。addObserver（self，selector：playerItemDidReachEnd：，name：AVPlayerItemDidPlayToEndTimeNotification，object：playerItem）;
self.layer.addSublayer（videoPlayerLayer！）
}
覆盖func observeValueForKeyPath（keyPath：String？，ofObject object：AnyObject ?, change：[String： AnyObject] ?, context：UnsafeMutablePointer< Void>）{
if keyPath！= nil&&的keyPath！ ==player.currentItem.status{
如果让newValue =更改？[NSKeyValueChangeNewKey] {
如果AVPlayerStatus（rawValue：newValue as！Int）== .ReadyToPlay {
playVideo（） / *播放状态更改为.ReadyToPlay * /
}
}
} else {
super.observeValueForKeyPath（keyPath，ofObject：object，change：change，context：context ）
}
}
func playerItemDidReachEnd（通知：NSNotification）{
让playerItem = notification.object as！ AVPlayerItem
playerItem.seekToTime（kCMTimeZero）
playVideo（）
}
func playVideo（）{
videoPlayerLayer？.player！。 play（）
}
I am trying to merge multiple videos using AVMutableComposition. The problem I face is that whenever I try to add any AVMutableVideoComposition for applying any instructions, my playback freezes in AVPlayer at exact 6 seconds duration.
Another interesting thing is that it plays fine if I play it in Photos app of iPad after exporting using same videoComposition. So why does it freezes in AVPlayer at 6 seconds?
Code:
AVMutableComposition *mutableComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *videoCompositionTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo
preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *audioCompositionTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio
preferredTrackID:kCMPersistentTrackID_Invalid];
for (AVURLAsset *asset in assets)
{
AVAssetTrack *assetTrack;
assetTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
AVAssetTrack *audioAssetTrack = [asset tracksWithMediaType:AVMediaTypeAudio].firstObject;
NSError *error;
[videoCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, assetTrack.timeRange.duration )
ofTrack:assetTrack
atTime:time
error:&error];
if (error) {
NSLog(@"asset url :: %@",assetTrack.asset);
NSLog(@"Error1 - %@", error.debugDescription);
}
[audioCompositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioAssetTrack.timeRange.duration)
ofTrack:audioAssetTrack
atTime:time
error:&error];
if (error) {
NSLog(@"Error2 - %@", error.debugDescription);
}
time = CMTimeAdd(time, assetTrack.timeRange.duration);
if (CGSizeEqualToSize(size, CGSizeZero)) {
size = assetTrack.naturalSize;;
}
}
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
AVMutableVideoCompositionLayerInstruction *videoTrackLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoCompositionTrack];
mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, time);
mainInstruction.layerInstructions = [NSArray arrayWithObjects:videoTrackLayerInstruction, nil];
AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];
mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake(1, 30);
mainCompositionInst.renderSize = size;
pi = [AVPlayerItem playerItemWithAsset:mutableComposition];
pi.videoComposition = mainCompositionInst;
Also, I know problem is mostly videoComposition because if I remove the videoComposition, then it plays fine on AVPlayer.
UPDATE 1: I just found out that when it freezes after 6 seconds, if I drag the slider back or forward(i.e. use seekToTime), it starts playing normally again without any further freeze.
Also audio keeps on playing fine even when video is frozen.
UPDATE 2: If I just go ahead and export it using AVAssetExportSession with same AVMutableComposition, and load asset from of exported video, it works fine. So its just when I play AVMutableComposition directly, problem arises.
Finally, I got the solution to fix this.
You should play after playerItem's status is changed to .ReadyToPlay.
Please see as below.
func startVideoPlayer() {
let playerItem = AVPlayerItem(asset: self.composition!)
playerItem.videoComposition = self.videoComposition!
let player = AVPlayer(playerItem: playerItem)
player.actionAtItemEnd = .None
videoPlayerLayer = AVPlayerLayer(player: player)
videoPlayerLayer!.frame = self.bounds
/* add playerItem's observer */
player.addObserver(self, forKeyPath: "player.currentItem.status", options: .New, context: nil)
NSNotificationCenter.defaultCenter().addObserver(self, selector: "playerItemDidReachEnd:", name: AVPlayerItemDidPlayToEndTimeNotification, object: playerItem);
self.layer.addSublayer(videoPlayerLayer!)
}
override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
if keyPath != nil && keyPath! == "player.currentItem.status" {
if let newValue = change?[NSKeyValueChangeNewKey] {
if AVPlayerStatus(rawValue: newValue as! Int) == .ReadyToPlay {
playVideo() /* play after status is changed to .ReadyToPlay */
}
}
} else {
super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
}
}
func playerItemDidReachEnd(notification: NSNotification) {
let playerItem = notification.object as! AVPlayerItem
playerItem.seekToTime(kCMTimeZero)
playVideo()
}
func playVideo() {
videoPlayerLayer?.player!.play()
}
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