Set rate at which AVSampleBufferDisplayLayer renders sample buffers

Question

I am using an AVSampleBufferDisplayLayer to display CMSampleBuffers which are coming over a network connection in the h.264 format. Video playback is smooth and working corr

Answer 1

The Timebase needs to be set to the presentation time stamp (pts) of the first frame you intend to decode. I was indexing the pts of the first frame to 0 by subtracting the initial pts from all subsequent pts and setting the Timebase to 0. For whatever reason, that didn't work.

You want something like this (called before a call to decode):

CMTimebaseRef controlTimebase;
CMTimebaseCreateWithMasterClock( CFAllocatorGetDefault(), CMClockGetHostTimeClock(), &controlTimebase );

displayLayer.controlTimebase = controlTimebase;

// Set the timebase to the initial pts here
CMTimebaseSetTime(displayLayer.controlTimebase, CMTimeMake(ptsInitial, 1));
CMTimebaseSetRate(displayLayer.controlTimebase, 1.0);

Set the PTS for the CMSampleBuffer...

CMSampleBufferSetOutputPresentationTimeStamp(sampleBuffer, presentationTimeStamp);

And maybe make sure display immediately isn't set....

CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanFalse);

This is covered very briefly in WWDC 2014 Session 513.