ref: bd30e1069a2783b4e1c7a5538d5ff711d6eca715
dir: /player/decode.c/
#include <stdio.h> #include <string.h> #include <errno.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include <fcntl.h> #include <stdlib.h> #include <math.h> #define MINIMP3_IMPLEMENTATION #include "decode.h" #define MIN(a, b) ((a) < (b) ? (a) : (b)) static void get_spectrum(decoder *dec, int numch) { int i, ch, band; const mp3dec_t *d = &dec->mp3d.mp3d; // Average spectrum power for 32 frequency band for (ch = 0; ch < numch; ch++) { for (band = 0; band < 32; band++) { float band_power = 0; for (i = 0; i < 9; i++) { float sample = d->mdct_overlap[ch][i + band*9]; band_power += sample*sample; } // with averaging //dec->spectrum[band][ch] += (band_power/9 - spectrum[band][ch]) * 0.25; // w/o averaging dec->spectrum[band][ch] = band_power/9; } } // Calculate dB scale from power for better visualization for (ch = 0; ch < numch; ch++) { for (band = 0; band < 32; band++) { float power = dec->spectrum[band][ch]; float db_offset = 100; // to shift dB values from [0..-inf] to [max..0] float db = 10*log10f(power + 1e-15) + db_offset; if (db < 0) db = 0; //printf("% .5f\t", db); } //printf("\n"); } } void decode_samples(decoder *dec, uint8_t *buf, int bytes) { memset(buf, 0, bytes); mp3dec_ex_read(&dec->mp3d, (mp3d_sample_t*)buf, bytes/sizeof(mp3d_sample_t)); } int open_dec(decoder *dec, const char *file_name) { if (!dec || !file_name || !*file_name) return 0; memset(dec, 0, sizeof(*dec)); mp3dec_ex_open(&dec->mp3d, file_name, MP3D_SEEK_TO_SAMPLE); if (!dec->mp3d.samples) return 0; return 1; } int close_dec(decoder *dec) { mp3dec_ex_close(&dec->mp3d); memset(dec, 0, sizeof(*dec)); }