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Altera_Forum's avatar
Altera_Forum
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16 years ago

Mp3 decoder too slow on NiosII

Hi,all

I'm now designing a mp3 player for DE2 board, which use libmad for mp3 decoding. But currently, the speed is too slow for real time playing. The core is NiosII fastest core,i cache=8kb, d cache=16kb, cpu clk is set to 100MHz. It still require 380s to decode a 274s mp3 file. Can anyone tell me, is it reasonable?

I have also tried to add custom instruction to replace the macro "mad_f_mul" in libmad, but the decoding speed remain the same or even worse. I can't understand it.

The platform I'm using is QuartusII 9.1.

any guidelines, thx!

20 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I just use the new CI marco in system.h. The gcc will not compile the new CI automatically? But it still give the correct results.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Have you enabled -O2 or -O3 ?

    If you rip out all calls into libc, can you fit the whole code into internal memory?

    (It might be that the resident set fits in the cache though.)
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    No, I get the result with optimization off. Does that make so much difference?

    I tired to enable -O3 once, but the program didn't work correctly, it seems the program stopped at some place and a lot of codes can't be executed, so I change it back to no optimization.

    I don't quite understand the meaning of "If you rip out all calls into libc, can you fit the whole code into internal memory? (It might be that the resident set fits in the cache though.)". I use the 512K sram as memory and the program size is 167K.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Definitely use -O3 - the speed-up is huge. Also, create onchip RAM and find the most often called functions and move them to this RAM until it's full.

    Bill
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Thank you. I shall try -O3 or -O2 again.

    I don't know how to create onchip RAM and move any function to it. I just know how to add the onchip RAM componet to the system using SOPC, what else should I do?
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    --- Quote Start ---

    Thank you. I shall try -O3 or -O2 again.

    I don't know how to create onchip RAM and move any function to it. I just know how to add the onchip RAM componet to the system using SOPC, what else should I do?

    --- Quote End ---

    Use this before functions going into onchip ram: 

    
void function(void) __attribute__((section(".onchip_mem")));
void function(void)
{
}
    Of course onchip_mem has to match the name used in SOPC.

    Bill
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    --- Quote Start ---

    cpu clk is set to 100Hz.

    --- Quote End ---

    I imagine cpu is set to 100MHz. If you are really using 100Hz cpu clk that might be the problem.