Duration not appearing for after Video

Question

I have recorded live video from the camera using AVCaptureVideoDataOuput and AVAssetWriter but the resulting video has no duration. Can anyone give a brief idea or a point in the general direction to get the duration working?

Are you setting [AVAssetWriter startSessionAtSourceTime] to the first sample buffer's PTS? Are you calling [AVAssetWriter finishWriting]? You should show some code. — Rhythmic Fistman, May 18 '12 at 09:17

score 2 · Accepted Answer · answered May 18 '12 at 11:36

What needs to be done is define an initial CMTime.

self.time = CMMakeTime( 0, 30 /* some frame time */ );

then

[instanceAVAssetWriter setSessionAtSourceTime:self.time];

on captureOutput:didOutputSampleBuffer:fromConnection:

CMSampleBufferRef sb;
CMSampleTimingInfo sampleTimingInfo;

sampleTimingInfo.duration = CMTimeMake(1,30);
sampleTimingInfo.presentationTimeStamp = self.time;
sampleTimingInfo.decodeTimeStamp = kCMTimeInvalid;

CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault, sampleBuffer, 1, &sampleTimingInfo, &sb);

and the end

CFRelease( sb );
self.time.value += 1;

Can't even describe the frustration this answer brought an end to. Thanks! — Clay Garrett, Nov 24 '15 at 19:56

score 0 · Answer 2 · answered May 18 '12 at 20:38

This is what I do which is similar to NebulaFox's answer. This code is in the callback for the capturing of video data. The writer has already been initialized and setup.

switch (writer.status) {
        case AVAssetWriterStatusUnknown:

            startTime = CMSampleBufferGetPresentationTimeStamp(sample);

            [writer startWriting];
            [writer startSessionAtSourceTime:startTime];

            if (writer.status != AVAssetWriterStatusWriting) {
                break ;
            }  
....

Duration not appearing for after Video

2 Answers2