苹果文档 https://web.archive.org/web/20140814091047/http://developer.apple.com/library/ios/DOCUMENTATION/AVFoundation/Reference/AVCaptureFileOutput_Class/Reference/Reference.html似乎表明在将视频录制到文件时，应用程序可以毫无问题地即时更改 URL。但我发现一个问题。当我尝试这个时，录制委托被调用并出现错误......
操作无法完成。 （操作系统状态错误-12780。）信息
字典是：{
AVErrorRecordingSuccessivelyFinishedKey = 0; }
（“couldn't”中的时髦单引号来自日志记录[错误本地化描述]）
这是代码，基本上是对 WWDC10 AVCam 示例的调整：
1) 开始录音。启动计时器每隔几秒更改一次输出 URL
- (void) startRecording
{
// start the chunk timer
self.chunkTimer = [NSTimer scheduledTimerWithTimeInterval:5
target:self
selector:@selector(chunkTimerFired:)
userInfo:nil
repeats:YES];
AVCaptureConnection *videoConnection = [AVCamCaptureManager connectionWithMediaType:AVMediaTypeVideo fromConnections:[[self movieFileOutput] connections]];
if ([videoConnection isVideoOrientationSupported]) {
[videoConnection setVideoOrientation:[self orientation]];
}
if ([[UIDevice currentDevice] isMultitaskingSupported]) {
[self setBackgroundRecordingID:[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{}]];
}
NSURL *fileUrl = [[ChunkManager sharedInstance] nextURL];
NSLog(@"now recording to %@", [fileUrl absoluteString]);
[[self movieFileOutput] startRecordingToOutputFileURL:fileUrl recordingDelegate:self];
}
2) 当定时器触发时，更改输出文件名而不停止录制
- (void)chunkTimerFired:(NSTimer *)aTimer {
if ([[UIDevice currentDevice] isMultitaskingSupported]) {
[self setBackgroundRecordingID:[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{}]];
}
NSURL *nextUrl = [self nextURL];
NSLog(@"changing capture output to %@", [[nextUrl absoluteString] lastPathComponent]);
[[self movieFileOutput] startRecordingToOutputFileURL:nextUrl recordingDelegate:self];
}
注意：[self nextURL] 生成文件 url，如 file-0.mov、file-5.mov、file-10.mov 等。
3）每次文件更改时都会调用此函数，并且每次其他调用都会出错......
- (void) captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
fromConnections:(NSArray *)connections
error:(NSError *)error
{
id delegate = [self delegate];
if (error && [delegate respondsToSelector:@selector(someOtherError:)]) {
NSLog(@"got an error, tell delegate");
[delegate someOtherError:error];
}
if ([self backgroundRecordingID]) {
if ([[UIDevice currentDevice] isMultitaskingSupported]) {
[[UIApplication sharedApplication] endBackgroundTask:[self backgroundRecordingID]];
}
[self setBackgroundRecordingID:0];
}
if ([delegate respondsToSelector:@selector(recordingFinished)]) {
[delegate recordingFinished];
}
}
运行时，file-0 被写入，然后我们在将 url 更改为 file-5 后看到错误 -12780，file-10 被写入，然后出现错误，然后正常，依此类推。
看来动态更改 URL 不起作用，但它会停止写入，从而允许下一个 URL 更改起作用。
