2011-06-23 10:45:46     what's the max ability of bf561 in decoder jpeg image?

2011-06-23 10:45:46     what's the max ability of bf561 in decoder jpeg image?

macgrady tracy (CHINA)

Message: 101614   

hi,

I have  try the  jpeg-6b in my blackfin531 board, use -O2 FLAGS in compiling and only use "C" code,  to my disappointing,  the lib can only decoder 2 pictures per second,  the  resolution of the picture is 1024x768.

my question is :

what is the max ability of blackfin561?

Can decoder 100 pictures(1024x768)  per seconds?

thanks!

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2011-06-23 10:51:35     Re: what's the max ability of bf561 in decoder jpeg image?

Mike Frysinger (UNITED STATES)

Message: 101616   

the jpeg code in the dist has Blackfin optimizations if you enable the config option.  make sure you're using 2010R1.

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2011-06-23 13:45:14     Re: what's the max ability of bf561 in decoder jpeg image?

macgrady tracy (CHINA)

Message: 101628   

thank u for u reply.

yes,i have enable the optimizations options, only one assamble file compliled when compiling.

Can u give me a estimate value of  the max ablity of bf561?

Can decoder 100 pictures of resolution 1024x768 per seconds?

I Think the code in the 2010R1 havn't been optimized enough.

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2011-06-23 13:52:54     Re: what's the max ability of bf561 in decoder jpeg image?

Mike Frysinger (UNITED STATES)

Message: 101629   

i have no idea.  we dont really compute metrics like that for library code.

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2011-06-24 03:01:51     Re: what's the max ability of bf561 in decoder jpeg image?

Simon Brewer (AUSTRALIA)

Message: 101642   

Just to help you out a little here.  On the BF561 there is an 133MHz 32 bit interface.

Some back of the envelope calculations: 1024x748x 3 (pixels) /2 (assume YUV420) x 100 (pictures second) = ~120 Mbytes/sec  You also need to write out the image to an output port e.g. PPI, so you at least need to double that number = 240Mbytes/sec.

You will find that at best you might get about 40% utilization out of your external bus, so expect about 200Mbyte/sec performance at best out of the BF561.  So there is not enough external bus bandwidth to do what you want.

Some other calcs.  1024x768x3x100= 2.4x10^8 pixels per second.  On a 2*550 MHz part that is about 4.7 cycles/pixel.  Not a lot of cycles to do useful work.  In summary, you don't have enough memory bandwidth, or cpu power to do what you want, regardless of any level of code optimization.

Simon

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2011-06-24 11:07:40     Re: what's the max ability of bf561 in decoder jpeg image?

macgrady tracy (CHINA)

Message: 101663   

hi, Simon

thank you very much for your suggestion!

I said 100 pictures per seconds not means i should decoder 100 pictures per seconds!

my application is as follows:

Use V4l to get a 1024x768 JPEG image and then decoder this picture to RGB24 used for my other algorithm.

for example:

i can only use 10% CPU ability to decoder jpeg image, and other 90% userd for algorithm.

and i should decoder 10 pictures every seconds(So i said i wanna decoder 100 pictures per second, and i ignore the bandwidth).

After complish the algorithm, i need not output my image.

thanks again

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2011-06-26 21:32:18     Re: what's the max ability of bf561 in decoder jpeg image?

Simon Brewer (AUSTRALIA)

Message: 101689   

> I said 100 pictures per seconds not means i should decoder 100 pictures per seconds!

Ok...

> i can only use 10% CPU ability to decoder jpeg image, and other 90% userd for algorithm.

You are still going to have the cycles/pel problem.  Like I said I estimate you need only have about 4 cycles/pel available to do the decompression.  You should probably look at dedicated JPEG hardware for this task.

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2011-06-27 05:44:49     Re: what's the max ability of bf561 in decoder jpeg image?

macgrady tracy (CHINA)

Message: 101709   

Thank you very much, I 'll try it, and i estimate i should use a jpeg dec SOC ic to realize this function.