Video Capture (webcam): [HACK] do synch frame notifications

[dscherba]

• Recent change moved webcam video capture to asynchronous
  signals towards upper layers
• But some upper layers (e.g. P4C) have heavyweight handlers
  • Heavyweight enough to not service the thread message queue
  • ... which can create a pileup of video frames

[dscherba]

//cc: @digitalmouse12 ( @willkelleher if he's still looking), @DinhNguyenCat

This sort of reverts timing to what webrtc would do. The issue with the asynchronous implementation is that if you have a slow network, or similar, our video encoding can slow down enough to not service the video frame queue quickly enough. This looks like a really bad (and unsurvivable) memory leak.

[willkelleher]

So is the "OnEncoded" handler blocking for too long when the network is slow, causing the encoder to slow down the capture handler thread, thereby building up a huge queue of frames that can't be handled?

[dscherba]

Didn't trace all the way down to onencoded, but the time across the video
encoder definitely increases. May be due to linkage with the onencoded/net
send stuff, could just be long encode time.

Either way, some more work should probably be done there, but until then
this is needed to make sure we don't pile-up/crash (this basically gives us
the old timing/behavior).
On Oct 8, 2015 6:00 PM, "Will Kelleher" notifications@github.com wrote:

So is the "OnEncoded" handler blocking for too long when the network is
slow, causing the encoder to slow down the capture handler thread, thereby
building up a huge queue of frames that can't be handled?

—
Reply to this email directly or view it on GitHub
#19 (comment).

[longk15t]

What does the phenomenon look like ? Is it about recording with webcam and video quality really bad/slow ? Just curious if I'm seeing same issue with you.

[dscherba]

@longk15t : this was in a call (low/constrained uplink) with a webcam. Video would be really sluggish/delayed and memory would start ramping hard until Personify crashed (out of memory).

[dscherba]

@DinhNguyenCat , @digitalmouse12 : any thoughts (note: feedback on this is lower priority than chroma stuff--not in critical path)?