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Diff: wave_player.cpp
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- 0:62c18ade9a60
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diff -r 000000000000 -r 62c18ade9a60 wave_player.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/wave_player.cpp Tue Jan 18 03:41:02 2011 +0000 @@ -0,0 +1,211 @@ +//----------------------------------------------------------------------------- +// a sample mbed library to play back wave files. +// +// explanation of wave file format. +// https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ + +// if VERBOSE is uncommented then the wave player will enter a verbose +// mode that displays all data values as it reads them from the file +// and writes them to the DAC. Very slow and unusable output on the DAC, +// but useful for debugging wave files that don't work. +//#define VERBOSE + + +#include <mbed.h> +#include <stdio.h> +#include <wave_player.h> + + +//----------------------------------------------------------------------------- +// constructor -- accepts an mbed pin to use for AnalogOut. Only p18 will work +wave_player::wave_player(AnalogOut *_dac) +{ + wave_DAC=_dac; + wave_DAC->write_u16(32768); //DAC is 0-3.3V, so idles at ~1.6V + verbosity=0; +} + +//----------------------------------------------------------------------------- +// if verbosity is set then wave player enters a mode where the wave file +// is decoded and displayed to the screen, including sample values put into +// the DAC FIFO, and values read out of the DAC FIFO by the ISR. The DAC output +// itself is so slow as to be unusable, but this might be handy for debugging +// wave files that don't play +//----------------------------------------------------------------------------- +void wave_player::set_verbosity(int v) +{ + verbosity=v; +} + +//----------------------------------------------------------------------------- +// player function. Takes a pointer to an opened wave file. The file needs +// to be stored in a filesystem with enough bandwidth to feed the wave data. +// LocalFileSystem isn't, but the SDcard is, at least for 22kHz files. The +// SDcard filesystem can be hotrodded by increasing the SPI frequency it uses +// internally. +//----------------------------------------------------------------------------- +void wave_player::play(FILE *wavefile) +{ + unsigned chunk_id,chunk_size,channel; + unsigned data,samp_int,i; + short unsigned dac_data; + long long slice_value; + char *slice_buf; + short *data_sptr; + unsigned char *data_bptr; + int *data_wptr; + FMT_STRUCT wav_format; + long slice,num_slices; + DAC_wptr=0; + DAC_rptr=0; + for (i=0;i<256;i+=2) { + DAC_fifo[i]=0; + DAC_fifo[i+1]=3000; + } + DAC_wptr=4; + DAC_on=0; + + fread(&chunk_id,4,1,wavefile); + fread(&chunk_size,4,1,wavefile); + while (!feof(wavefile)) { + if (verbosity) + printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size); + switch (chunk_id) { + case 0x46464952: + fread(&data,4,1,wavefile); + if (verbosity) { + printf("RIFF chunk\n"); + printf(" chunk size %d (0x%x)\n",chunk_size,chunk_size); + printf(" RIFF type 0x%x\n",data); + } + break; + case 0x20746d66: + fread(&wav_format,sizeof(wav_format),1,wavefile); + if (verbosity) { + printf("FORMAT chunk\n"); + printf(" chunk size %d (0x%x)\n",chunk_size,chunk_size); + printf(" compression code %d\n",wav_format.comp_code); + printf(" %d channels\n",wav_format.num_channels); + printf(" %d samples/sec\n",wav_format.sample_rate); + printf(" %d bytes/sec\n",wav_format.avg_Bps); + printf(" block align %d\n",wav_format.block_align); + printf(" %d bits per sample\n",wav_format.sig_bps); + } + if (chunk_size > sizeof(wav_format)) + fseek(wavefile,chunk_size-sizeof(wav_format),SEEK_CUR); + break; + case 0x61746164: +// allocate a buffer big enough to hold a slice + slice_buf=(char *)malloc(wav_format.block_align); + if (!slice_buf) { + printf("Unable to malloc slice buffer"); + exit(1); + } + num_slices=chunk_size/wav_format.block_align; + samp_int=1000000/(wav_format.sample_rate); + if (verbosity) { + printf("DATA chunk\n"); + printf(" chunk size %d (0x%x)\n",chunk_size,chunk_size); + printf(" %d slices\n",num_slices); + printf(" Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate)); + printf(" programmed interrupt tick interval=%d\n",samp_int); + } + +// starting up ticker to write samples out -- no printfs until tick.detach is called + if (verbosity) + tick.attach_us(this,&wave_player::dac_out, 500000); + else + tick.attach_us(this,&wave_player::dac_out, samp_int); + DAC_on=1; + +// start reading slices, which contain one sample each for however many channels +// are in the wave file. one channel=mono, two channels=stereo, etc. Since +// mbed only has a single AnalogOut, all of the channels present are averaged +// to produce a single sample value. This summing and averaging happens in +// a variable of type signed long long, to make sure that the data doesn't +// overflow regardless of sample size (8 bits, 16 bits, 32 bits). +// +// note that from what I can find that 8 bit wave files use unsigned data, +// while 16 and 32 bit wave files use signed data +// + for (slice=0;slice<num_slices;slice+=1) { + fread(slice_buf,wav_format.block_align,1,wavefile); + if (feof(wavefile)) { + printf("Oops -- not enough slices in the wave file\n"); + exit(1); + } + data_sptr=(short *)slice_buf; // 16 bit samples + data_bptr=(unsigned char *)slice_buf; // 8 bit samples + data_wptr=(int *)slice_buf; // 32 bit samples + slice_value=0; + for (channel=0;channel<wav_format.num_channels;channel++) { + switch (wav_format.sig_bps) { + case 16: + if (verbosity) + printf("16 bit channel %d data=%d ",channel,data_sptr[channel]); + slice_value+=data_sptr[channel]; + break; + case 32: + if (verbosity) + printf("32 bit channel %d data=%d ",channel,data_wptr[channel]); + slice_value+=data_wptr[channel]; + break; + case 8: + if (verbosity) + printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]); + slice_value+=data_bptr[channel]; + break; + } + } + slice_value/=wav_format.num_channels; + +// slice_value is now averaged. Next it needs to be scaled to an unsigned 16 bit value +// with DC offset so it can be written to the DAC. + switch (wav_format.sig_bps) { + case 8: slice_value<<=8; + break; + case 16: slice_value+=32768; + break; + case 32: slice_value>>=16; + slice_value+=32768; + break; + } + dac_data=(short unsigned)slice_value; + if (verbosity) + printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data); + DAC_fifo[DAC_wptr]=dac_data; + DAC_wptr=(DAC_wptr+1) & 0xff; + while (DAC_wptr==DAC_rptr) { + } + } + DAC_on=0; + tick.detach(); + free(slice_buf); + break; + case 0x5453494c: + if (verbosity) + printf("INFO chunk, size %d\n",chunk_size); + fseek(wavefile,chunk_size,SEEK_CUR); + break; + default: + printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size); + data=fseek(wavefile,chunk_size,SEEK_CUR); + break; + } + fread(&chunk_id,4,1,wavefile); + fread(&chunk_size,4,1,wavefile); + } +} + + +void wave_player::dac_out() +{ + if (DAC_on) { +#ifdef VERBOSE + printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]); +#endif + wave_DAC->write_u16(DAC_fifo[DAC_rptr]); + DAC_rptr=(DAC_rptr+1) & 0xff; + } +} +