On Wed, 06 Feb 2008 03:41:46 +0100, Scott C. Frase <[EMAIL PROTECTED]>
wrote:
On Wed, 2008-02-06 at 01:35 +0100, Herman Robak wrote:
http://www.heroinewarrior.com/cinelerra/cinelerra.html#VIDEO-OUT
...
"If you have lots of memory and more than one CPU, this option can
improve
playback performance by decoding video on one CPU as fast as possible
while dedicating other CPU to displaying video only. It assumes all
playback operations are forward and no frames are dropped. Operations
involving reverse playback or frame dropping are negatively impacted."
I was dismayed that I could only enable it if "play every frame"
was toggled, but it _certainly_ helped forward playback! Now there
were no pauses around edits anymore. (my laptop is a Core Duo)
Backward playback, however, was slooow.
...
Herman,
I tested the code change tonight. Previous to making the change, I
didn't have a problem or slow downs playing back HDV video, as my box is
pretty powerful. I usually get 30FPS on video that isn't under a
transition or effect of some kind. This performance was achieved with
"Play Every Frame" and "Decode Frames Async" off.
On my 2GHz dual/dual Opteron (two CPUs with two cores each) I only got
1-2 frames per second unless I started playback at the beginning of the
timeline; then I got the full 25 fps. If I stopped playback and started
it again, I got the miserable 1-2 fps. If I placed the cursor somewhere
on the timeline, likewise.
This was a regression. It wasn't like this a couple of years ago, and
the one-bit fix that we've both tried out brought back the previous
performance.
When I enabled "PEF &
Decode frames asynchronously", my video playback slowed down terribly,
to 6-8fps.
I did not try out this setting prior to the one-bit patch. I would not
have noticed any improvement, for that matter (1-2 fps, remember?)
Now that I got full framerate I was eager to find a way to get read of
the brief freeze around cut points. Do you get those?
Then I made the code change and recompiled. I found no difference while
"Play Every Frame" and "Decode frames asynchronously" were unchecked.
However, I did see that playback improved when those two options were
selected. Playback increased to about 20fps. Alas, when playback would
hit an effect or transition, it would slow down quite a bit.
For my taste, I will stick with "Play Every Frame" and "Decode.."
switched off.
There is more ...
This is what _our_ version of the manual says:
"Play every frame
This causes every frame of video to be displayed even if it means that the
playback of the video track(s) will fall behind. This option should always
be enabled unless you use uncompressed codecs. As of 1/2007, most
compressed codecs do not support frame dropping anymore."
http://cv.cinelerra.org/docs/split_manual_en/cinelerra_cv_manual_en_3.html#SEC53
What is the source of this statement? The recommendation seems completely
unworkable and misguided to me. If you don't allow frame dropping, the
video will easily get out of synch with the audio.
--
Herman Robak
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