Oliver Seitz wrote:
If you have to use mjpeg for
playback, go buying several of the fastest harddisks (like 10000rpm
types) and connect them in RAID0 or RAID5 array. That might give
bandwith that can cope with mjpeg.
Wouldn't storing the file on a RAM disk potentially also work, if disk
throughput is the problem?
It most surely would. If there's enough RAM for it. I've got a mjpeg
encoded 720p-video without sound here. It plays less than five minutes and
the file is 885MByte.
Faster is always better, but I've been using mjpeg encoding for quite a
while (for various reasons) and seldom run into any throughput problems
with it. In fact one of the reasons I use it is because it uses very
little cpu power and I can run it on very underpowered machines. With
newer video chipsets of course the decoding isn't really a problem even
with "real" codecs, but I've gotten used to using mjpeg at high quality
settings and am happy with it.
As a reference, I have a 1264 x 528 mjpeg file that's about 3 1/2
minutes long. It's 571 MB and runs at about 22 mbps. This works out to
around 2 1/2 MB per second which almost any drive can handle. I use a
cache setting of 8192 and get smooth playback on a 1.8 Ghz Sempron
processor with 1 Gig of ram, a 5400 rpm drive, and an nvidia 5700
graphics card. The video has lots of solid blocks of graphics moving
from right to left across the screen and it all runs very smoothly on
this machine (using about 30% cpu under windows xp).
If however, I add sharpening to the mplayer command line, the cpu goes
to 85% and the clip starts stuttering pretty badly. This is of course
all with mplayer; windows media player doesn't like the odml files
created by mencoder and quicktime just doesn't play back smoothly enough
with low powered machines - at least under windows.
I can even play 1024 x 768 mjpeg clips on a via cpu with on board
graphics with little problem either, but only under linux.
While mjpeg does use a lot of disk space and bandwidth, I really not
sure that it's your core problem. As I mentioned above, sharpening or
other filters can add a lot of overhead and maybe a little tweaking of
your command line can yield some information as to what's going on.
good luck,
morris
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