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Altera_Forum's avatar
Altera_Forum
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14 years ago

DE2-115 - MP3 decoding from Flash with libMAD - searching examples

Hello Alteraforum,

I am searching for help, with the libMAD, because it drives me mad. :) I am working on an easy example to decode a MP3-file from flash, decode it into sram and output the PCM from there.

I have verified, that the output is working. So when I read an PCM (16bit, 44.1kHz) from the flash and output it, it plays nice. I then tried to write and read from sram, no problem. I then tried the same with a MP3 and libMAD. As codebase I tried to adept the minimad.c example, but I do not get it working and I even can't really determine where the error occurs. There is audio output, but just plain noise.

Has someone here an easy example for the DE2-Family that he would share with me, where you decode an MP3 with libMAD and use the Wolfson to output the data?

(please don't refer to the Neek-Example, because there they do so much more to output the id-tags and read the files, I have looked quite deep into that example already).

I think my problem lies somewhere in the scale function or I get mixed up with the endians.

Any example code would be really appreciated.

Yours, Peter.

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Ok, I got it running now. The problem was the output method of the minimad.c example. I have now written some new code for it, see below. 

             
//j is a global variable, that i use to count the length of the pcm. 
//I use it to output from the sram in another method
 
        while (nsamples--) {
        	unsigned int sample;
        	
            //i am sure, that i only decode stereo, so I don't check nsamples == 2
            unsigned int audioausgabe = 0;
            //sample = scale(*left_ch++);
            sample = (*left_ch++);
            audioausgabe = sample&0xFFFF;
            audioausgabe = audioausgabe << 16;
            //sample = scale(*right_ch++);
            sample = (*right_ch++);
            audioausgabe = audioausgabe|(sample & 0xFFFF);
            //write to sram the resulting 32bit word
            IOWR(SRAM_BASE,j,audioausgabe);
            j++;
          }
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Could you provide me with the working project?

    Jeff Goeders

    jeffrey.goeders (GMAIL)