wave_player.cpp

00001 
00002  
00003 #include <mbed.h>
00004 #include <stdio.h>
00005 #include <wave_player.h>
00006  
00007 Serial pc(USBTX, USBRX);
00008 //-----------------------------------------------------------------------------
00009 // constructor -- accepts an mbed pin to use for AnalogOut.  Only p18 will work
00010 wave_player::wave_player(AnalogOut *_dac)
00011 {
00012   wave_DAC=_dac;
00013   wave_DAC->write_u16(32768);        //DAC is 0-3.3V, so idles at ~1.6V
00014   verbosity=0;
00015 }
00016  
00017 //-----------------------------------------------------------------------------
00018 // if verbosity is set then wave player enters a mode where the wave file
00019 // is decoded and displayed to the screen, including sample values put into
00020 // the DAC FIFO, and values read out of the DAC FIFO by the ISR.  The DAC output
00021 // itself is so slow as to be unusable, but this might be handy for debugging
00022 // wave files that don't play
00023 //-----------------------------------------------------------------------------
00024 void wave_player::set_verbosity(int v)
00025 {
00026   verbosity=v;
00027 }
00028  
00029 //-----------------------------------------------------------------------------
00030 // player function.  Takes a pointer to an opened wave file.  The file needs
00031 // to be stored in a filesystem with enough bandwidth to feed the wave data.
00032 // LocalFileSystem isn't, but the SDcard is, at least for 22kHz files.  The
00033 // SDcard filesystem can be hotrodded by increasing the SPI frequency it uses
00034 // internally.
00035 //-----------------------------------------------------------------------------
00036 void wave_player::play(FILE *wavefile)
00037 {
00038         unsigned chunk_id,chunk_size,channel;
00039         unsigned data,samp_int,i;
00040         short unsigned dac_data;
00041         long long slice_value;
00042         char *slice_buf;
00043         short *data_sptr;
00044         unsigned char *data_bptr;
00045         int *data_wptr;
00046         FMT_STRUCT wav_format;
00047         long slice,num_slices;
00048   DAC_wptr=0;
00049   DAC_rptr=0;
00050   for (i=0;i<256;i+=2) {
00051     DAC_fifo[i]=0;
00052     DAC_fifo[i+1]=3000;
00053   }
00054   DAC_wptr=4;
00055   DAC_on=0;
00056  
00057   fread(&chunk_id,4,1,wavefile);
00058   fread(&chunk_size,4,1,wavefile);
00059   while (!feof(wavefile)) {
00060     if (verbosity)
00061       pc.printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size);
00062     switch (chunk_id) {
00063       case 0x46464952:
00064         fread(&data,4,1,wavefile);
00065         if (verbosity) {
00066           pc.printf("RIFF chunk\n");
00067           pc.printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00068           pc.printf("  RIFF type 0x%x\n",data);
00069         }
00070         pc.printf("case1\n");
00071         break;
00072       case 0x20746d66:
00073         fread(&wav_format,sizeof(wav_format),1,wavefile);
00074         if (verbosity) {
00075           pc.printf("FORMAT chunk\n");
00076           pc.printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00077           pc.printf("  compression code %d\n",wav_format.comp_code);
00078           pc.printf("  %d channels\n",wav_format.num_channels);
00079           pc.printf("  %d samples/sec\n",wav_format.sample_rate);
00080           pc.printf("  %d bytes/sec\n",wav_format.avg_Bps);
00081           pc.printf("  block align %d\n",wav_format.block_align);
00082           pc.printf("  %d bits per sample\n",wav_format.sig_bps);
00083         }
00084         if (chunk_size > sizeof(wav_format))
00085           fseek(wavefile,chunk_size-sizeof(wav_format),SEEK_CUR);
00086          pc.printf("case2\n");
00087         break;
00088       case 0x61746164:
00089 // allocate a buffer big enough to hold a slice
00090         slice_buf=(char *)malloc(wav_format.block_align);
00091         if (!slice_buf) {
00092           pc.printf("Unable to malloc slice buffer");
00093           exit(1);
00094         }
00095         num_slices=chunk_size/wav_format.block_align;
00096         samp_int=1000000/(wav_format.sample_rate);
00097         if (verbosity) {
00098           pc.printf("DATA chunk\n");
00099           pc.printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00100           pc.printf("  %d slices\n",num_slices);
00101           pc.printf("  Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate));
00102           pc.printf("  programmed interrupt tick interval=%d\n",samp_int);
00103         }
00104  
00105 // starting up ticker to write samples out -- no printfs until tick.detach is called
00106         if (verbosity)
00107           tick.attach_us(this,&wave_player::dac_out, 500000); 
00108         else
00109           tick.attach_us(this,&wave_player::dac_out, samp_int); 
00110         DAC_on=1; 
00111  
00112 // start reading slices, which contain one sample each for however many channels
00113 // are in the wave file.  one channel=mono, two channels=stereo, etc.  Since
00114 // mbed only has a single AnalogOut, all of the channels present are averaged
00115 // to produce a single sample value.  This summing and averaging happens in
00116 // a variable of type signed long long, to make sure that the data doesn't
00117 // overflow regardless of sample size (8 bits, 16 bits, 32 bits).
00118 //
00119 // note that from what I can find that 8 bit wave files use unsigned data,
00120 // while 16 and 32 bit wave files use signed data
00121 //
00122         for (slice=0;slice<num_slices;slice+=1) {
00123           fread(slice_buf,wav_format.block_align,1,wavefile);
00124           if (feof(wavefile)) {
00125             pc.printf("Oops -- not enough slices in the wave file\n");
00126             exit(1);
00127           }
00128           data_sptr=(short *)slice_buf;     // 16 bit samples
00129           data_bptr=(unsigned char *)slice_buf;     // 8 bit samples
00130           data_wptr=(int *)slice_buf;     // 32 bit samples
00131           slice_value=0;
00132           for (channel=0;channel<wav_format.num_channels;channel++) {
00133             
00134             switch (wav_format.sig_bps) {
00135               case 16:
00136                 if (verbosity)
00137                   pc.printf("16 bit channel %d data=%d ",channel,data_sptr[channel]);
00138                 slice_value+=data_sptr[channel];
00139                 break;
00140               case 32:
00141                 if (verbosity)
00142                   pc.printf("32 bit channel %d data=%d ",channel,data_wptr[channel]);
00143                 slice_value+=data_wptr[channel];
00144                 break;
00145               case 8:
00146                 if (verbosity)
00147                   pc.printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]);
00148                 slice_value+=data_bptr[channel];
00149                 break;
00150             }
00151           }
00152           slice_value/=wav_format.num_channels;
00153           
00154 // slice_value is now averaged.  Next it needs to be scaled to an unsigned 16 bit value
00155 // with DC offset so it can be written to the DAC.
00156           switch (wav_format.sig_bps) {
00157             case 8:     slice_value<<=8;
00158                         break;
00159             case 16:    slice_value+=32768;
00160                         break;
00161             case 32:    slice_value>>=16;
00162                         slice_value+=32768;
00163                         break;
00164           }
00165           dac_data=(short unsigned)slice_value;
00166           if (verbosity)
00167             pc.printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data);
00168           DAC_fifo[DAC_wptr]=dac_data*volume; //--> modified: adjusting the volume
00169           
00170           //controls end     
00171           DAC_wptr=(DAC_wptr+1) & 0xff;
00172           while (DAC_wptr==DAC_rptr) {
00173           }
00174         }
00175         DAC_on=0;
00176         tick.detach();
00177         free(slice_buf);
00178          pc.printf("case3\n");
00179         break;
00180       case 0x5453494c:
00181         if (verbosity)
00182           pc.printf("INFO chunk, size %d\n",chunk_size);
00183         fseek(wavefile,chunk_size,SEEK_CUR);
00184          pc.printf("case4\n");
00185         break;
00186       default:
00187         pc.printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
00188         data=fseek(wavefile,chunk_size,SEEK_CUR);
00189         break;
00190     }
00191     fread(&chunk_id,4,1,wavefile);
00192     fread(&chunk_size,4,1,wavefile);
00193   }
00194 }
00195  
00196  
00197 void wave_player::dac_out()
00198 {
00199   if (DAC_on) {
00200 #ifdef VERBOSE
00201   pc.printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]);
00202 #endif
00203     wave_DAC->write_u16(DAC_fifo[DAC_rptr]);
00204     DAC_rptr=(DAC_rptr+1) & 0xff;
00205   }
00206 }