On Tue, Mar 18, 2008 at 2:14 PM, Philip Heron <[email protected]> wrote:
> [email protected] wrote:
> > On Sat, Mar 15, 2008 at 4:01 PM, Philip Heron <[email protected]> wrote:
> >> Hi all,
> >>
> >> Attached is a trivial patch that speeds up encoding for key frame only
> >> streams. It skips the motion vector search which is not needed when
> >> there are never going to be any delta frames. It was made against
> >> thusnelda SVN revision 14589.
> >
> > The results of the current frame's (and previous frame's) MV search
> > are needed by subsequent frames to seed constant speed and constant
> > accelleration candidates. That includes INTRA frames. This breaks
> > that part of the analysis.
> >
> > It would be valid to skip MV analysis on scene-change INTRA frames so
> > long as you also reset the persistent MV analysis state, but it is
> > incorrect behavior for INTRA frames forced by the keyframe max
> > interval.
>
> Is it possible to skip MV analysis completly as a speedup, and still
> produce a valid bitstream? Or am I barking up the wrong tree? I'm trying
> to encode full screen video (720x576x25fps) in real time for
> transmission on a LAN, so speed is more important than efficiency.
Valid, yes. You'll just end up with partly nonsensical motion vectors
for the two frames after-- also, having low-quality candidate vectors
from a previous frame will slightly slow down the search in later
frames as the code may decide to 'throw away' the inadequate candidate
vectors and start a search from scratch.
If you want Thusnelda speed now, turn off halfpel MV and get ASM
replacements for BInterSAD* in place in mode.c.
Monty
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