David D. Hagood wrote:
Also,
many of the operations in video codecs are multiply-and-accumulate
operations ( a += b*c ), which DSPs have a single instruction to do.
In short, clock per clock, I suspect the DSP can do more video work than
the ARM can.
Well OMAP 1710 is ARM5-TEJ - the E letter means EDSP extensions so it
has MAC operations too.
Remember what step 0 of optimization is: MEASURE IT FIRST!
Until somebody can actually measure where all the time is going, making
pronouncements like "It's slow because of X - I just know it" are the
root of all evil - you spend a great deal of time tweaking that one
thing only to find out that it was only 1% of the time to begin with.
True. Well, as for the measuring, I only know my Tungsten T2 (OMAP
1510,168Mhz) can play 320x240, 25FPS, 300Kbits mp4 videos better than my
N770. And TCPMP (palmos video player) uses ARM core only. So I suppose
even ARM4 core is good enough. I guess 250Mhz ARM5 together with DSP
helping with decoding audio (and maybe some video step - blitting with
color space conversion?) could do much better.
You can watch /sys/devices/platform/dsp/loadinfo while playing video,
the DSP is constantly at 100% when playing video.
But I admit these are just my theories. I still had no time to
investigate gstreamer framework on N770 in detail.
Frantisek
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