[Theora-dev] Theora camera/fast computers

Andrey Filippov theora at elphel.com
Wed Mar 23 09:10:30 PST 2005

Hi Ivan,

thanks for the testing - it gives me hope that it is possible to find a
computer that can do the job - I'll compare options and order one.

> Notes:
>  - the picture is not always smooth,
>    probably because of mplayer being single-threaded -
>    the peak load is not distributed over several frames,
>    so one or several frames become slightly delayed when the decoder
>    encounters an "extra expensive" frame

Did you notice if it were INTRA frames? In those clips they are exactly
frame 0, frame 256, and so on. You could see them on the video as they
"sweep" away some faint "turbulence" left by moving objects.

>  - adding "-framedrop" to the command line does not change timing, nor
>    the smoothness, i.e. the delays are under the threshhold where mplayer
>    begins to decimate frames

I can't imagine how "-framedrop"  could help with INTER frames - only
rendering could be skipped.

>  - this is the non-experimental decoder with the decoder-specific
>    MMX patches applied. It is the fastest decoder of those which I could
> test.
> My guess is that on a 3.3GHz hardware you will be fine for scenes like
> that one
> but possibly not when there is plenty of motion, like an exhibition
> hall...

So I'll just point the camera in such a way, that only a fraction of the
field will be moving :-)

> You would be fine though with even a slightly smaller resolution, due to
> the
> quadratic reduction in complexity.

Yes, that's true but I'm trying to demonstrate the camera-limited
performance. And for practical applications - I just hope that while
cameras are coming to full production, less expensive multi-core CPUs will
become available, as well as better optimized decoders. And maybe just the
existence of Elphel Model 333 cameras will add some challenge to the
software developers and that faster players will appear sooner :-)

BTW, now there are some experimental 333 cameras built and tested and we
will be able to give away several for the development purposes - i.e. as a
source of the high resolution/high frame rate Ogg/Theora video (Ogg
streamer is not implemented yet, but I hope will be soon). And of course,
possible hacking is not limited to the player - camera itself is not less
open (but still much less documented :-( ).


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