Thank you. That helps. I was not able to use your script. I copied the
script in a text file and I execute it in terminal like that:
jrls-pro:~ jrls$ chmod +x /Users/jrls/Desktop/ram.sh
jrls-pro:~ jrls$ chmod 0755 /Users/jrls/Desktop/ram.sh
jrls-pro:~ jrls$ /Users/jrls/Desktop/ram.sh
Usage: newRamDisk.sh <size in MB>
Example: newRamDisk.sh 20
But nothing appends after that. Will there be a new drive in the Finder?
Anyway, I tried another script found at : http://snippets.dzone.com/posts/show/1808
(the script posted below) and it gave me a new image with the size I
specified. I've put my movie inside and I did some tests.
From hard drive
Movie loader Asynch mode off : 27
Movie loader Asynch mode on : 27
Movie's cache hint on : 28
From ram disk
Movie loader Asynch mode off : 25
Movie loader Asynch mode on : 28
Movie's cache hint on : 27
It was difficult to find an average frame rate because it moves quite
a lot.
So, this is quite similar in any case. Use a jpeg compression instead
of dv helped.
Thanks.
Le 08-02-27 à 13:10, Michael Diehr a écrit :
On Feb 27, 2008, at 7:41 AM, Christopher Wright wrote:
I want to read a movie in loop (approx. 3 sec.) amongs others
synthetised images. When I start the movie (dv compression, 30
fps, 720x480), I'm seing the frame rate lowering (about 15 fps
instead of 30 without the movie playing). I checked my processor
and it's still not very hight (about 40%). I presumed that the
diskdrive reading the movie would slow down the frame rate?
You can try setting "Synchronous Mode" on the Movie Loader, and see
if that helps. Some tests show that this setting may improve QT's
movie caching stuff.
So, I wonder, is it possible to put my little movie directly in
RAM to avoid to read it from the hard drive?
There's some way of making a ram disk. I don't know how in OS X,
but people have mentioned it, and I'm sure there are docs on how to
do it.
I just completed some tests on a very similar setup, and here's what
I found:
Movies loading from hard disk:
* Movieloader Asynch mode off : ~20 fps
* Movieloader Asynch mode ON : ~30 fps
* Movie's "cache hint" ON : ~33 fps
Movies loading from ram disk:
* Movieloader Asynch mode ON : ~40 fps
* Movie's "cache hint" ON : ~43 fps
As mentioned before, I think it's odd that QC is so un-aggressive
about caching entire movies (and/or individual movie frames).
So the best performance is given with a combination of:
Movie:
use as few pixels as possible (e.g. 640x480 or lower, if
quality is ok)
use a hiqh quality, low-CPU codec such as Motion JPEG / High
enable the movie file's Cache in RAM hint
(open in quicktime player then apple-J, then select video track)
Movieloader :
enable Asynch mode
disable high quality
disable deinterlacing
RAMdisk:
use one!
Here's a script to create a ram disk.
Save this as a text file, chmod 755, and then run from the terminal:
#!/bin/sh
if [ $# -ne 1 ]
then
echo " Usage: newRamDisk.sh <size in MB>"
echo "Example: newRamDisk.sh 20"
exit
fi
if [ $1 -lt 4 ]
then
echo "Error: Size must be greater than or equal to four megabytes"
exit
fi
volName="RamDisk$1"
ramDiskSize=`echo "${1}*2048" | bc`
echo "Allocating $ramDiskSize blocks"
mydev=`hdid -nomount ram://${ramDiskSize}`
echo -n "Create/erase HFS Plus filesystem named $volName on $mydev"
diskutil eraseVolume HFS+ $volName $mydev
exit
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