I think in absolute time you are right, the "P" points do not move.
Instead everything else would move left by .5, resulting in the same
image I described with the vertical arrows always tilting to the right.
The green decision lines move left by .5 to align with the "P" points
since the decision is strictly whether a "T" is between two "P".
The "T" points move left by .5 because the client will have to timestamp
everything .5 earlier.
I still feel it would be less confusing to avoid negative numbers and to
match what I am pretty certain is mainstream usage of integer timestamps
on frames.
Pekka Paalanen wrote:
On Mon, 10 Feb 2014 12:20:00 -0800
Bill Spitzak <spit...@gmail.com> wrote:
Pekka Paalanen wrote:
This algorithm aims to start showing an update between t-T/2 and t+T/2,
which means that presentation may occur a little early or late, with
an "average" of zero. Another option would be to show the update between
t and t+T, which would mean that presentation would be always late with
an "average" of T/2.
I think there would be a lot less confusion if this was described using
the t,t+1 model. I think in your diagram it would move the 'P' line .5
to the right so they line up with the green lines, and all the red
arrows would tilt to the right. It makes no difference to the result
(the same frames are selected) but I think makes it a lot easier to
describe.
Another reason is that media starts at time 0, not time -.5*frame.
Hmm, I'm not sure. The green lines are not frame boundaries, they are
decision boundaries. In the picture, the points P are the exact time
when a framebuffer flip happens, which means that the hardware starts
to scan out a new image. Each image is shown for the interval
P[n]..P[n+1], not the interval between green lines.
So the green lines only divide the queue axis into intervals, that get
assigned to a particular P. Both axes are the same time axis, with
units of nanoseconds which are not marked. The black ticks on both axes
denote when a new frame begins.
Did we have some confusion here?
- pq
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