wave_player.cpp

00001 //-----------------------------------------------------------------------------
00002 // a sample mbed library to play back wave files.
00003 //
00004 // explanation of wave file format.
00005 // https://ccrma.stanford.edu/courses/422/projects/WaveFormat/
00006 
00007 // if VERBOSE is uncommented then the wave player will enter a verbose
00008 // mode that displays all data values as it reads them from the file
00009 // and writes them to the DAC.  Very slow and unusable output on the DAC,
00010 // but useful for debugging wave files that don't work.
00011 //#define VERBOSE
00012 
00013 
00014 #include <mbed.h>
00015 #include <stdio.h>
00016 #include <wave_player.h>
00017 
00018 extern void send_led2();
00019 
00020 
00021 
00022 //-----------------------------------------------------------------------------
00023 // constructor -- accepts an mbed pin to use for AnalogOut.  Only p18 will work
00024 wave_player::wave_player(AnalogOut *_dac, DigitalOut *_amp_enable)
00025 {
00026   wave_DAC=_dac;
00027   wave_DAC->write_u16(32768);        //DAC is 0-3.3V, so idles at ~1.6V
00028   verbosity=0;
00029   sound_stop = 0;
00030   Amp_Enable= _amp_enable;
00031   *Amp_Enable = 1;
00032 }
00033 
00034 //-----------------------------------------------------------------------------
00035 // if verbosity is set then wave player enters a mode where the wave file
00036 // is decoded and displayed to the screen, including sample values put into
00037 // the DAC FIFO, and values read out of the DAC FIFO by the ISR.  The DAC output
00038 // itself is so slow as to be unusable, but this might be handy for debugging
00039 // wave files that don't play
00040 //-----------------------------------------------------------------------------
00041 void wave_player::set_verbosity(int v)
00042 {
00043   verbosity=v;
00044 }
00045 
00046 //-----------------------------------------------------------------------------
00047 // player function.  Takes a pointer to an opened wave file.  The file needs
00048 // to be stored in a filesystem with enough bandwidth to feed the wave data.
00049 // LocalFileSystem isn't, but the SDcard is, at least for 22kHz files.  The
00050 // SDcard filesystem can be hotrodded by increasing the SPI frequency it uses
00051 // internally.
00052 //-----------------------------------------------------------------------------
00053 void wave_player::play(FILE *wavefile)
00054 {
00055         unsigned chunk_id,chunk_size,channel;
00056         unsigned data,samp_int,i;
00057         short unsigned dac_data;
00058         long long slice_value;
00059         char *slice_buf;
00060         short *data_sptr;
00061         unsigned char *data_bptr;
00062         int *data_wptr;
00063         FMT_STRUCT wav_format;
00064         long slice,num_slices;
00065   DAC_wptr=0;
00066   DAC_rptr=0;
00067   for (i=0;i<256;i+=2) {
00068     DAC_fifo[i]=0;
00069     DAC_fifo[i+1]=3000;
00070   }
00071   DAC_wptr=4;
00072   DAC_on=0;
00073   play_count = 0;
00074   *Amp_Enable = 1;
00075 
00076   fread(&chunk_id,4,1,wavefile);
00077   fread(&chunk_size,4,1,wavefile);
00078   while ((!feof(wavefile))&&(sound_stop==0)) {
00079     if (verbosity)
00080       printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size);
00081     switch (chunk_id) {
00082       case 0x46464952:
00083         fread(&data,4,1,wavefile);
00084         if (verbosity) {
00085           printf("RIFF chunk\n");
00086           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00087           printf("  RIFF type 0x%x\n",data);
00088         }
00089         break;
00090       case 0x20746d66:
00091         fread(&wav_format,sizeof(wav_format),1,wavefile);
00092         if (verbosity) {
00093           printf("FORMAT chunk\n");
00094           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00095           printf("  compression code %d\n",wav_format.comp_code);
00096           printf("  %d channels\n",wav_format.num_channels);
00097           printf("  %d samples/sec\n",wav_format.sample_rate);
00098           printf("  %d bytes/sec\n",wav_format.avg_Bps);
00099           printf("  block align %d\n",wav_format.block_align);
00100           printf("  %d bits per sample\n",wav_format.sig_bps);
00101         }
00102         if (chunk_size > sizeof(wav_format))
00103           fseek(wavefile,chunk_size-sizeof(wav_format),SEEK_CUR);
00104         break;
00105       case 0x61746164:
00106 // allocate a buffer big enough to hold a slice
00107         slice_buf=(char *)malloc(wav_format.block_align);
00108         if (!slice_buf) {
00109           printf("Unable to malloc slice buffer");
00110           exit(1);
00111         }
00112         num_slices=chunk_size/wav_format.block_align;
00113         samp_int=1000000/(wav_format.sample_rate);
00114         if (verbosity) {
00115           printf("DATA chunk\n");
00116           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00117           printf("  %d slices\n",num_slices);
00118           printf("  Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate));
00119           printf("  programmed interrupt tick interval=%d\n",samp_int);
00120         }
00121 
00122 // starting up ticker to write samples out -- no printfs until tick.detach is called
00123         if (verbosity)
00124           tick.attach_us(this,&wave_player::dac_out, 500000); 
00125         else
00126           tick.attach_us(this,&wave_player::dac_out, samp_int); 
00127         DAC_on=1; 
00128 
00129 // start reading slices, which contain one sample each for however many channels
00130 // are in the wave file.  one channel=mono, two channels=stereo, etc.  Since
00131 // mbed only has a single AnalogOut, all of the channels present are averaged
00132 // to produce a single sample value.  This summing and averaging happens in
00133 // a variable of type signed long long, to make sure that the data doesn't
00134 // overflow regardless of sample size (8 bits, 16 bits, 32 bits).
00135 //
00136 // note that from what I can find that 8 bit wave files use unsigned data,
00137 // while 16 and 32 bit wave files use signed data
00138 //
00139           for (slice=0;slice<num_slices;slice+=1) {
00140           fread(slice_buf,wav_format.block_align,1,wavefile);
00141           if (feof(wavefile)) {
00142             printf("Oops -- not enough slices in the wave file\n");
00143             exit(1);
00144           }
00145           play_count++;
00146           if( play_count > 100 )
00147           {
00148               *Amp_Enable = 0;
00149           }
00150           if( sound_stop == 1 )
00151           {
00152              tick.detach();
00153              free(slice_buf);
00154              sound_stop = 0;
00155              return;
00156           }
00157 
00158           data_sptr=(short *)slice_buf;     // 16 bit samples
00159           data_bptr=(unsigned char *)slice_buf;     // 8 bit samples
00160           data_wptr=(int *)slice_buf;     // 32 bit samples
00161           slice_value=0;
00162           for (channel=0;channel<wav_format.num_channels;channel++) {
00163 
00164           if( sound_stop == 1 )
00165           {
00166              tick.detach();
00167              free(slice_buf);
00168              sound_stop = 0;
00169               return;
00170           }
00171             switch (wav_format.sig_bps) {
00172               case 16:
00173                 if (verbosity)
00174                   printf("16 bit channel %d data=%d ",channel,data_sptr[channel]);
00175                 slice_value+=data_sptr[channel];
00176                 break;
00177               case 32:
00178                 if (verbosity)
00179                   printf("32 bit channel %d data=%d ",channel,data_wptr[channel]);
00180                 slice_value+=data_wptr[channel];
00181                 break;
00182               case 8:
00183                 if (verbosity)
00184                   printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]);
00185                 slice_value+=data_bptr[channel];
00186                 break;
00187             }
00188           }
00189           slice_value/=wav_format.num_channels;
00190           
00191 // slice_value is now averaged.  Next it needs to be scaled to an unsigned 16 bit value
00192 // with DC offset so it can be written to the DAC.
00193           switch (wav_format.sig_bps) {
00194             case 8:     slice_value<<=8;
00195                         break;
00196             case 16:    slice_value+=32768;
00197                         break;
00198             case 32:    slice_value>>=16;
00199                         slice_value+=32768;
00200                         break;
00201           }
00202           dac_data=(short unsigned)slice_value;
00203           if (verbosity)
00204             printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data);
00205           DAC_fifo[DAC_wptr]=dac_data;
00206           DAC_wptr=(DAC_wptr+1) & 0xff;
00207           while (DAC_wptr==DAC_rptr) {
00208           }
00209         }
00210         DAC_on=0;
00211         tick.detach();
00212         free(slice_buf);
00213         break;
00214       case 0x5453494c:
00215         if (verbosity)
00216           printf("INFO chunk, size %d\n",chunk_size);
00217         fseek(wavefile,chunk_size,SEEK_CUR);
00218         break;
00219       default:
00220         printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
00221         data=fseek(wavefile,chunk_size,SEEK_CUR);
00222         break;
00223     }
00224     fread(&chunk_id,4,1,wavefile);
00225     fread(&chunk_size,4,1,wavefile);
00226   }
00227   sound_stop = 0;
00228 }
00229 
00230 
00231 void wave_player::dac_out()
00232 {
00233   if (DAC_on) {
00234 #ifdef VERBOSE
00235   printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]);
00236 #endif
00237     wave_DAC->write_u16(DAC_fifo[DAC_rptr]);
00238     DAC_rptr=(DAC_rptr+1) & 0xff;
00239   }
00240 }
00241 
00242 void wave_player::set_s_stop(void)
00243 {
00244     sound_stop = 1;
00245 }
00246 
00247 
00248