Hi,
this one was an experiment
/n/sources/contrib/maht/actionfs.c
invoked with a regex like actionfs (file.mpg).([0-9]+).(ppm)
if you then
cat /n/actionfs/file.mpg.100.ppm
actionfs responds with the output from executing
/bin/action-read $fd file.mpg.100.ppm file.mpg 100 ppm
where $fd will be an fd to write to
i.e. trivially action-read would be something like
----
#!/bin/rc
fd = $1
shift
echo $* > /fd/$fd
-----
The coresponding action-write also works
----
#!/bin/rc
fd = $1
shift
cat /fd/$fd > /dev/null # or whatever
-----
I wrote it specifically to extract individual frames from video files using
ffmpeg on Linux and
bring them into Plan9 for processing but generalized the arguments in case I
thought of something
interesting later.
My first round of experiment went like this
cpu% cat /bin/action-read
#!/bin/rc
# expect fd fullname videoname frameno
fname = `{echo -n $3 | tr ! '/'}
{
ssh storm single_frame $fname $4
} > /fd/$1
cpu% cat /n/storm/home/maht/bin/single_frame
#!/usr/local/plan9/bin/rc
# expect filename frameno
timer = `{echo $2 | awk ' { printf "%d.%02d\n", $1/ 25, 4 * ($1 % 25) }'}
{
ffmpeg -i $1 -t 00.001 -ss $timer /tmp/frame_$pid ^_%d.ppm
cat /tmp/frame_$pid ^_1.ppm
rm -f frame_$pid ^_1.ppm
rm -f frame_$pid ^_2.ppm # stupid ffmpeg outputs 2 frames (sometimes)
} >[2] /dev/null
I was then using imgfs to calculate the average rgb value to look for black
frames but (unsurprisingly) it was taking too long (4 secs per frame) esp. as
the Plan9 I was using is in Qemu, cue installing Plan 9 on my terminal.
The ffmpeg part on the Linux side (2Ghz Opteron) was taking 1 second on its own
so I have to come up with some sort of look ahead cache which is contrary to
the idea, I may as well just convert the whole file to ppms at the start! I've
not looked if it is I/O or CPU - perhaps a bit of both.
I've not got round to doing it on my fresh terminal yet. I've got a new 3.2Ghz
Dual Xeon server to migrate to and a Quad Core terminal to play with so we'll
see how that works out.
I was hoping to get Xcpu in there but I couldn't see how to get the Plan9 part
working though I have the Linux bits up.
I have a couple of decent OSX boxes available too (one PPC one Intel) but I
gave up getting it to compile :)
too many projects .....
matt
