[mythtv] AVSync2 Refinements

Mark Kendall mark.kendall at gmail.com
Fri Dec 13 08:15:10 UTC 2019

On Wed, 11 Dec 2019 at 14:14, Tim Pletcher <pletchtd at gmail.com> wrote:
> If anyone is interested, I threw together a crude simulation to theoretically demonstrate the different control responses with the various control options (plot shown at: https://imgur.com/a/DDBxcQR).  On the the plot, the green line is the gain only implementation and the red line is the gain + filter implementation provided in the second patch revision. The control loop will settle in around the process mean which includes the jitter / noise so it may have a little zero offset but this should not be enough to be evident for the user.


Out of curiosity - could that zero offset be estimated?

I ask because at some point I would like to test adding a couple of
additional a/v sync adjustments - and clearly the greater the accuracy
the better.

The first adjustment is to account for FFmpeg hardware deinterlacers
(currently only VAAPI VVP - but may add NVDEC soon) that do a little
buffering. As they are processed after a/v sync, we will need to pass
back an offset - probably on the next pass.

The second is to handle a/v sync adjustments that are
required/reported by displays via the EDID. I recently added some EDID
parsing to our code and it only requires a few extra lines to parse
out the sync adjustments required when displaying with interlaced and
progressive modelines.


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