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 //Serial pc(USBTX, USBRX);
00019 //-----------------------------------------------------------------------------
00020 // constructor -- accepts an mbed pin to use for AnalogOut.  Only p18 will work
00021 wave_player::wave_player(AnalogOut *_dac)
00022 {
00023   wave_DAC=_dac;
00024   wave_DAC->write_u16(32768);        //DAC is 0-3.3V, so idles at ~1.6V
00025   verbosity=0;
00026   play_state=1;
00027 }
00028 
00029 //-----------------------------------------------------------------------------
00030 // if verbosity is set then wave player enters a mode where the wave file
00031 // is decoded and displayed to the screen, including sample values put into
00032 // the DAC FIFO, and values read out of the DAC FIFO by the ISR.  The DAC output
00033 // itself is so slow as to be unusable, but this might be handy for debugging
00034 // wave files that don't play
00035 //-----------------------------------------------------------------------------
00036 void wave_player::set_verbosity(int v)
00037 {
00038   verbosity=v;
00039 }
00040 
00041 void wave_player::set_play_state(int p) 
00042 {
00043     play_state = p;
00044 }
00045 
00046 int wave_player::get_play_state()
00047 {
00048     return play_state;
00049 }
00050 
00051 //-----------------------------------------------------------------------------
00052 // player function.  Takes a pointer to an opened wave file.  The file needs
00053 // to be stored in a filesystem with enough bandwidth to feed the wave data.
00054 // LocalFileSystem isn't, but the SDcard is, at least for 22kHz files.  The
00055 // SDcard filesystem can be hotrodded by increasing the SPI frequency it uses
00056 // internally.
00057 //-----------------------------------------------------------------------------
00058 void wave_player::play(FILE *wavefile)
00059 {
00060         unsigned chunk_id,chunk_size,channel;
00061         unsigned data,samp_int,i;
00062         //short unsigned dac_data;
00063         long long slice_value;
00064         char *slice_buf;
00065         short *data_sptr;
00066         unsigned char *data_bptr;
00067         int *data_wptr;
00068         FMT_STRUCT wav_format;
00069         long slice,num_slices;
00070   DAC_wptr=0;
00071   DAC_rptr=0;
00072   for (i=0;i<256;i+=2) {
00073     DAC_fifo[i]=0;
00074     DAC_fifo[i+1]=3000;
00075   }
00076   DAC_wptr=4;
00077   DAC_on=0;
00078 
00079   fread(&chunk_id,4,1,wavefile);
00080   fread(&chunk_size,4,1,wavefile);
00081   while (!feof(wavefile) && play_state) {
00082     if (verbosity)
00083       printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size);
00084     switch (chunk_id) {
00085       case 0x46464952:
00086         fread(&data,4,1,wavefile);
00087         if (verbosity) {
00088           printf("RIFF chunk\n");
00089           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00090           printf("  RIFF type 0x%x\n",data);
00091         }
00092         break;
00093       case 0x20746d66:
00094         fread(&wav_format,sizeof(wav_format),1,wavefile);
00095         if (verbosity) {
00096           printf("FORMAT chunk\n");
00097           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00098           printf("  compression code %d\n",wav_format.comp_code);
00099           printf("  %d channels\n",wav_format.num_channels);
00100           printf("  %d samples/sec\n",wav_format.sample_rate);
00101           printf("  %d bytes/sec\n",wav_format.avg_Bps);
00102           printf("  block align %d\n",wav_format.block_align);
00103           printf("  %d bits per sample\n",wav_format.sig_bps);
00104         }
00105         if (chunk_size > sizeof(wav_format))
00106           fseek(wavefile,chunk_size-sizeof(wav_format),SEEK_CUR);
00107         break;
00108       case 0x61746164:
00109 // allocate a buffer big enough to hold a slice
00110         slice_buf=(char *)malloc(wav_format.block_align);
00111         if (!slice_buf) {
00112           printf("Unable to malloc slice buffer");
00113           exit(1);
00114         }
00115         num_slices=chunk_size/wav_format.block_align;
00116         samp_int=1000000/(wav_format.sample_rate);
00117         if (verbosity) {
00118           printf("DATA chunk\n");
00119           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00120           printf("  %d slices\n",num_slices);
00121           printf("  Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate));
00122           printf("  programmed interrupt tick interval=%d\n",samp_int);
00123         }
00124 
00125 // starting up ticker to write samples out -- no printfs until tick.detach is called
00126         if (verbosity)
00127           tick.attach_us(this,&wave_player::dac_out, 500000); 
00128         else
00129           tick.attach_us(this,&wave_player::dac_out, samp_int); 
00130         DAC_on=1; 
00131 
00132 // start reading slices, which contain one sample each for however many channels
00133 // are in the wave file.  one channel=mono, two channels=stereo, etc.  Since
00134 // mbed only has a single AnalogOut, all of the channels present are averaged
00135 // to produce a single sample value.  This summing and averaging happens in
00136 // a variable of type signed long long, to make sure that the data doesn't
00137 // overflow regardless of sample size (8 bits, 16 bits, 32 bits).
00138 //
00139 // note that from what I can find that 8 bit wave files use unsigned data,
00140 // while 16 and 32 bit wave files use signed data
00141 //
00142         for (slice=0;slice<num_slices;slice+=1) {
00143           fread(slice_buf,wav_format.block_align,1,wavefile);
00144           if (feof(wavefile)) {
00145             printf("Oops -- not enough slices in the wave file\n");
00146             exit(1);
00147           }
00148           data_sptr=(short *)slice_buf;     // 16 bit samples
00149           data_bptr=(unsigned char *)slice_buf;     // 8 bit samples
00150           data_wptr=(int *)slice_buf;     // 32 bit samples
00151           slice_value=0;
00152           for (channel=0;channel<wav_format.num_channels;channel++) {
00153             switch (wav_format.sig_bps) {
00154               case 16:
00155                 if (verbosity)
00156                   printf("16 bit channel %d data=%d ",channel,data_sptr[channel]);
00157                 slice_value+=data_sptr[channel];
00158                 break;
00159               case 32:
00160                 if (verbosity)
00161                   printf("32 bit channel %d data=%d ",channel,data_wptr[channel]);
00162                 slice_value+=data_wptr[channel];
00163                 break;
00164               case 8:
00165                 if (verbosity)
00166                   printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]);
00167                 slice_value+=data_bptr[channel];
00168                 break;
00169             }
00170           }
00171           slice_value/=wav_format.num_channels;
00172           
00173 // slice_value is now averaged.  Next it needs to be scaled to an unsigned 16 bit value
00174 // with DC offset so it can be written to the DAC.
00175         
00176           switch (wav_format.sig_bps) {
00177             case 8:     slice_value<<=8;
00178                         break;
00179             case 16:    slice_value+=32768;
00180                         break;
00181             case 32:    slice_value>>=16;
00182                         slice_value+=32768;
00183                         break;
00184           }
00185           dac_data=(short unsigned)slice_value;
00186           if (verbosity)
00187             printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data);
00188           DAC_fifo[DAC_wptr]=dac_data;
00189           
00190           DAC_fifo2[DAC_wptr]=dac_data;
00191           //pc.printf("buffer data: %x\n", DAC_fifo[DAC_wptr]);
00192           
00193           DAC_wptr=(DAC_wptr+1) & 0xff;
00194           while (DAC_wptr==DAC_rptr) {
00195           }
00196         }
00197         DAC_on=0;
00198         tick.detach();
00199         free(slice_buf);
00200         break;
00201       case 0x5453494c:
00202         if (verbosity)
00203           printf("INFO chunk, size %d\n",chunk_size);
00204         fseek(wavefile,chunk_size,SEEK_CUR);
00205         break;
00206       default:
00207         printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
00208         data=fseek(wavefile,chunk_size,SEEK_CUR);
00209         break;
00210     }
00211     fread(&chunk_id,4,1,wavefile);
00212     fread(&chunk_size,4,1,wavefile);
00213   }
00214 }
00215 
00216 
00217 void wave_player::dac_out()
00218 {
00219   if (DAC_on) {
00220 #ifdef VERBOSE
00221   printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]);
00222 #endif
00223     wave_DAC->write_u16(DAC_fifo[DAC_rptr]);
00224     DAC_rptr=(DAC_rptr+1) & 0xff;
00225   }
00226 }
00227 
00228