我正在用AVAssetWriter
录制视频(用户也可以切换到音频)。我在应用程序启动时开始录制。但是第一帧是黑色(或非常暗)。当我从音频切换到视频时也会发生这种情况。感觉就像AVAssetWriter
和/或AVAssetWriterInput
尚未准备好记录。我怎么能避免这个?
我不知道这是否是一个有用的信息,但我也使用GLKView
来显示视频。
func start_new_record(){
do{
try self.file_writer=AVAssetWriter(url: self.file_url!, fileType: AVFileTypeMPEG4)
if video_on{
if file_writer.canAdd(video_writer){
file_writer.add(video_writer)
}
}
if file_writer.canAdd(audio_writer){
file_writer.add(audio_writer)
}
}catch let e as NSError{
print(e)
}
}
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!){
guard is_recording else{
return
}
guard CMSampleBufferDataIsReady(sampleBuffer) else{
print("data not ready")
return
}
guard let w=file_writer else{
print("video writer nil")
return
}
if w.status == .unknown && start_recording_time==nil{
if (video_on && captureOutput==video_output) || (!video_on && captureOutput==audio_output){
print("START RECORDING")
file_writer?.startWriting()
start_recording_time=CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
file_writer?.startSession(atSourceTime: start_recording_time!)
}else{
return
}
}
if w.status == .failed{
print("failed /", w.error ?? "")
return
}
if captureOutput==audio_output{
if audio_writer.isReadyForMoreMediaData{
if !video_on || (video_on && video_written){
audio_writer.append(sampleBuffer)
//print("write audio")
}
}else{
print("audio writer not ready")
}
}else if video_output != nil && captureOutput==video_output{
if video_writer.isReadyForMoreMediaData{
video_writer.append(sampleBuffer)
if !video_written{
print("added 1st video frame")
video_written=true
}
}else{
print("video writer not ready")
}
}
}
SWIFT 4
解决方案#1:
我在启动应用程序时尽快调用file_writer?.startWriting()解决了这个问题。然后当你想开始录制时,执行file_writer?.startSession(atSourceTime:...)。
当您完成录制并调用finishRecording时,当您收到完整的回调时,再次设置一个新的写入会话。
解决方案#2:
我通过在调用AVAssetWriter.startSession时将起始时间加半秒来解决这个问题,如下所示:
start_recording_time = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
let startingTimeDelay = CMTimeMakeWithSeconds(0.5, 1000000000)
let startTimeToUse = CMTimeAdd(start_recording_time!, startingTimeDelay)
file_writer?.startSession(atSourceTime: startTimeToUse)
解决方案#3:
这里更好的解决方案是记录您收到的第一帧的时间戳并决定写入,然后用它开始您的会话。那你就不需要任何延迟了:
//Initialization, elsewhere:
var is_session_started = false
var videoStartingTimestamp = CMTime.invalid
// In code where you receive frames that you plan to write:
if (!is_session_started) {
// Start writing at the timestamp of our earliest sample
videoStartingTimestamp = currentTimestamp
print ("First video sample received: Starting avAssetWriter Session: \(videoStartingTimestamp)")
avAssetWriter?.startSession(atSourceTime: videoStartingTimestamp)
is_session_started = true
}
// add the current frame
pixelBufferAdapter?.append(myPixelBuffer, withPresentationTime: currentTimestamp)
好吧,愚蠢的错误......
当启动应用程序时,我初始化我的AVCaptureSession
,添加输入,输出等等。我只是在调用start_new_record
有点太快,就在我的捕获会话上调用commitConfiguration
之前。
至少我的代码可能对某些人有用。