Just a thought as you are only mentioning DVD-O-Matic...
Maybe DVD-O-Matic uses an older version of FFMPEG that isn't as
multithreaded as the one used in *DCP*-O-Matic?
I'm just curious if it's something 'silly', as Carl said, in the software
that creates the bottleneck.
Best regards,
Jonathan
On Mon, Dec 16, 2013 at 2:15 AM, Carsten Kurz <audiovisual(a)t-online.de>wrote;wrote:
Am 16.12.2013 um 01:17 schrieb Carl Hetherington:
I guess the encoding threads are being starved.
Maybe a screenshot of the taskmanager showing the individual core/thread
loads (must be quite impressing anyway with 16 individual load scales ;-) ?
If the 'master thread' is starving the encode threads, we would probably
see one or two threads at 100% and all the others at something between 30%
and 50%?
I already suggested to this user to do a test with a second instance of
DVD-o-matic encoding the SINTEL Trailer in parallel a second time. If the
single main thread is the bottleneck, both encodes would still run for
roughly the same time as a single encode at something like 90-100% total
CPU load. Would be another hint.
For the same reason, using multiple fast network clients will be of little
use - besides the aspect of gigabit network saturation beginning at
probably 10fps total node encoding capability, the master
application/thread will starve the network nodes just as well around
10-12fps for the same reason, I guess. Only segmented offloading of the
complete conversion could solve that - but then (partial) source and target
files would have to be located on all remote machines, distributed and
collected/assembled before/afterwards. That sounds like a lot of work - for
a relatively small group of users being able to benefit ;-)
If the machine has enough memory, means, no major swapping, I, too, think
disc performance is nearly irrelevant, as typically both input and output
is compressed and thus comparatively small and read/written quickly.
Actually I am not citing these benchmarks to suggest a major modification
of the framework to improve the performance for this high end machine class
- again that could be a lot of work for a rather small user base. My real
intention with these numbers is to find the sweetspot where a moderately
priced machine will deliver maximum throughput with DVD-o-matic. It seems
that currently this is a single CPU 6-8 core HT machine and something
around 10-12fps where DVD-o-matic maxes out under practical conditions.
But maybe, minor changes to the program framework and FFMPEG calls could
still improve the thread balancing somewhat.
This issue, however, should be solved once we see a GPU accelerated
version of OpenJPEG ;-)
- Carsten
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