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 
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 
00025     wave_DAC->write_u16(32768);        //DAC is 0-3.3V, so idles at ~1.6V
00026     verbosity=0;
00027     volumeMod=0;
00028 }
00029 int * wave_player:: getVolumeMod() 
00030 {
00031 
00032         return & volumeMod;
00033 
00034     }
00035 
00036 //-----------------------------------------------------------------------------
00037 // if verbosity is set then wave player enters a mode where the wave file
00038 // is decoded and displayed to the screen, including sample values put into
00039 // the DAC FIFO, and values read out of the DAC FIFO by the ISR.  The DAC output
00040 // itself is so slow as to be unusable, but this might be handy for debugging
00041 // wave files that don't play
00042 //-----------------------------------------------------------------------------
00043 void wave_player::set_verbosity(int v)
00044 {
00045     verbosity=v;
00046 }
00047 
00048 //-----------------------------------------------------------------------------
00049 // player function.  Takes a pointer to an opened wave file.  The file needs
00050 // to be stored in a filesystem with enough bandwidth to feed the wave data.
00051 // LocalFileSystem isn't, but the SDcard is, at least for 22kHz files.  The
00052 // SDcard filesystem can be hotrodded by increasing the SPI frequency it uses
00053 // internally.
00054 //-----------------------------------------------------------------------------
00055 void wave_player::play(FILE *wavefile,bool *ptr)
00056 {
00057     unsigned chunk_id,chunk_size,channel;
00058     unsigned data,samp_int,i;
00059     short unsigned dac_data;
00060     long long slice_value;
00061     char *slice_buf;
00062     short *data_sptr;
00063     unsigned char *data_bptr;
00064     int *data_wptr;
00065     FMT_STRUCT wav_format;
00066     long slice,num_slices;
00067     DAC_wptr=0;
00068     DAC_rptr=0;
00069     for (i=0; i<256; i+=2) {
00070         DAC_fifo[i]=0;
00071         DAC_fifo[i+1]=3000;
00072     }
00073     DAC_wptr=4;
00074     DAC_on=0;
00075 
00076     fread(&chunk_id,4,1,wavefile);
00077     fread(&chunk_size,4,1,wavefile);
00078     while (!feof(wavefile)) {
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                     if(*ptr==0)
00141                         break;
00142                     fread(slice_buf,wav_format.block_align,1,wavefile);
00143                     if (feof(wavefile)) {
00144                         printf("Oops -- not enough slices in the wave file\n");
00145                         exit(1);
00146                     }
00147                     data_sptr=(short *)slice_buf;     // 16 bit samples
00148                     data_bptr=(unsigned char *)slice_buf;     // 8 bit samples
00149                     data_wptr=(int *)slice_buf;     // 32 bit samples
00150                     slice_value=0;
00151                     for (channel=0; channel<wav_format.num_channels; channel++) {
00152                         switch (wav_format.sig_bps) {
00153                             case 16:
00154                                 if (verbosity)
00155                                     printf("16 bit channel %d data=%d ",channel,data_sptr[channel]);
00156                                 slice_value+=data_sptr[channel];
00157                                 break;
00158                             case 32:
00159                                 if (verbosity)
00160                                     printf("32 bit channel %d data=%d ",channel,data_wptr[channel]);
00161                                 slice_value+=data_wptr[channel];
00162                                 break;
00163                             case 8:
00164                                 if (verbosity)
00165                                     printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]);
00166                                 slice_value+=data_bptr[channel];
00167                                 break;
00168                         }
00169                     }
00170                     slice_value/=wav_format.num_channels;
00171 
00172 // slice_value is now averaged.  Next it needs to be scaled to an unsigned 16 bit value
00173 // with DC offset so it can be written to the DAC.
00174                     switch (wav_format.sig_bps) {
00175                         case 8:
00176                             slice_value<<=8;
00177                             break;
00178                         case 16:
00179                             slice_value+=32768;
00180                             break;
00181                         case 32:
00182                             slice_value>>=16;
00183                             slice_value+=32768;
00184                             break;
00185                     }
00186                     dac_data=(short unsigned)slice_value;
00187                     if (verbosity)
00188                         printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data);
00189                     DAC_fifo[DAC_wptr]=dac_data;
00190                     DAC_wptr=(DAC_wptr+1) & 0xff;
00191                     while (DAC_wptr==DAC_rptr) {
00192                     }
00193                 }
00194                 DAC_on=0;
00195                 tick.detach();
00196                 free(slice_buf);
00197                 break;
00198             case 0x5453494c:
00199                 if (verbosity)
00200                     printf("INFO chunk, size %d\n",chunk_size);
00201                 fseek(wavefile,chunk_size,SEEK_CUR);
00202                 break;
00203             default:
00204                 printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
00205                 data=fseek(wavefile,chunk_size,SEEK_CUR);
00206                 break;
00207         }
00208         fread(&chunk_id,4,1,wavefile);
00209         fread(&chunk_size,4,1,wavefile);
00210     }
00211 }
00212 
00213 
00214 void wave_player::dac_out()
00215 {
00216 
00217     if (DAC_on) {
00218 #ifdef VERBOSE
00219         printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]);
00220 #endif
00221 
00222         wave_DAC->write_u16(DAC_fifo[DAC_rptr] * (16 - volumeMod)>>4);
00223 
00224         DAC_rptr=(DAC_rptr+1) & 0xff;
00225     }
00226     
00227 
00228 }
00229