问题
I want to play video backward in AVPlayer. I have tried with changing rates property to -1.0, and although it did work it was not smooth. Is there any way through which I can smoothly play videos backward?
回答1:
As stated in the comments, the problem is with keyframes and the fact that most codecs are not designed to play backwards. There are 2 options for re-encoding the video that doesn't require you to actually reverse the video in editing.
- Make every frame a keyframe. I've seen this work well for codecs like H.264 that rely on keyframes. Basically if every frame is a key frame, then each frame can be decoded without relying on any previous frames so it's effectively the same as playing forward.
- Use a codec that doesn't use keyframes and non-keyframes (basically all frames are always keyframes). PhotoJPEG is one such option, although I'm not completely sure if it plays back on iOS. I would think so. It works great on a Mac.
Note that either of this options will result in larger file sizes compared to typical "keyframe every x frames" encoded video.
回答2:
You have to reach at the end of the current item and then set the rate to the negative value. Something like this:
-(void)reversePlay
{
CMTime durTime = myPlayer.currentItem.asset.duration;
if (CMTIME_IS_VALID(durTime))
{
[myPlayer seekToTime:durTime toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero];
[myPlayer setRate:-1.0];
}
else
NSLog(@"Invalid time");
}
source: https://stackoverflow.com/a/16104363/701043
来源：https://stackoverflow.com/questions/11902203/reverse-video-playback-in-ios