+static int try_get_bitrate(unsigned char *buf, int buf_size)
+{
+ int offs1, offs = 0;
+ int ret;
+
+ while (1)
+ {
+ offs1 = mp3_find_sync_word(buf + offs, buf_size - offs);
+ if (offs1 < 0)
+ return -2;
+ offs += offs1;
+ if (buf_size - offs < 4)
+ return -3;
+
+ // printf("trying header %08x\n", *(int *)(buf + offs));
+
+ ret = mpeg1_l3_bitrates[buf[offs + 2] >> 4];
+ if (ret > 0)
+ return ret;
+ }
+
+ return -2;
+}
+
+int mp3_get_bitrate(void *f_, int len)
+{
+ unsigned char buf[2048];
+ FILE *f = f_;
+ int retval = -1;
+ int ret;
+
+ memset(buf, 0, sizeof(buf));
+
+ fseek(f, 0, SEEK_SET);
+ ret = fread(buf, 1, sizeof(buf), f);
+ if (ret != sizeof(buf))
+ goto out;
+
+ ret = try_get_bitrate(buf, sizeof(buf));
+ if (ret <= 0) {
+ // try to read somewhere around the middle
+ fseek(f, len / 2, SEEK_SET);
+ ret = fread(buf, 1, sizeof(buf), f);
+ if (ret == sizeof(buf))
+ ret = try_get_bitrate(buf, sizeof(buf));
+ }
+ if (ret > 0)
+ retval = ret;
+
+ //printf("bitrate: %i\n", retval);
+
+out:
+ fseek(f, 0, SEEK_SET);
+ return retval;
+}
+
+void mp3_start_play(void *f_, int pos1024)
+{
+ unsigned char buf[2048];
+ FILE *f = f_;
+ int ret;
+
+ mp3_file_len = mp3_file_pos = 0;
+ mp3_current_file = NULL;
+ cdda_out_pos = 0;
+ decoder_active = 0;
+
+ if (!(PicoOpt & POPT_EN_MCD_CDDA) || f == NULL) // cdda disabled or no file?
+ return;
+
+ fseek(f, 0, SEEK_END);
+ mp3_file_len = ftell(f);
+
+ // search for first sync word, skipping stuff like ID3 tags
+ while (mp3_file_pos < 128*1024) {
+ int offs, bytes;
+
+ fseek(f, mp3_file_pos, SEEK_SET);
+ bytes = fread(buf, 1, sizeof(buf), f);
+ if (bytes < 4)
+ break;
+ offs = mp3_find_sync_word(buf, bytes);
+ if (offs >= 0) {
+ mp3_file_pos += offs;
+ break;
+ }
+ mp3_file_pos += bytes - 3;
+ }
+
+ // seek..
+ if (pos1024 != 0) {
+ unsigned long long pos64 = mp3_file_len - mp3_file_pos;
+ pos64 *= pos1024;
+ mp3_file_pos += pos64 >> 10;
+ }
+
+ ret = mp3dec_start(f, mp3_file_pos);
+ if (ret != 0) {
+ return;
+ }
+
+ mp3_current_file = f;
+ decoder_active = 1;
+
+ mp3dec_decode(mp3_current_file, &mp3_file_pos, mp3_file_len);
+}
+
+void mp3_update(int *buffer, int length, int stereo)
+{
+ int length_mp3, shr = 0;
+ void (*mix_samples)(int *dest_buf, short *mp3_buf, int count) = mix_16h_to_32;
+
+ if (mp3_current_file == NULL || mp3_file_pos >= mp3_file_len)
+ return; /* no file / EOF */
+
+ if (!decoder_active)
+ return;
+
+ length_mp3 = length;
+ if (PsndRate <= 11025 + 100) {
+ mix_samples = mix_16h_to_32_s2;
+ length_mp3 <<= 2; shr = 2;
+ }
+ else if (PsndRate <= 22050 + 100) {
+ mix_samples = mix_16h_to_32_s1;
+ length_mp3 <<= 1; shr = 1;
+ }
+
+ if (1152 - cdda_out_pos >= length_mp3) {
+ mix_samples(buffer, cdda_out_buffer + cdda_out_pos * 2,
+ length * 2);
+
+ cdda_out_pos += length_mp3;
+ } else {
+ int ret, left = 1152 - cdda_out_pos;
+
+ if (left > 0)
+ mix_samples(buffer, cdda_out_buffer + cdda_out_pos * 2,
+ (left >> shr) * 2);
+
+ ret = mp3dec_decode(mp3_current_file, &mp3_file_pos,
+ mp3_file_len);
+ if (ret == 0) {
+ cdda_out_pos = length_mp3 - left;
+ mix_samples(buffer + (left >> shr) * 2,
+ cdda_out_buffer,
+ (cdda_out_pos >> shr) * 2);
+ } else
+ cdda_out_pos = 0;
+ }
+}
+