mp3_drmp3.c 1.5 KB

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  1. /*
  2. * MP3 decoding using dr_mp3
  3. * (C) kub, 2020
  4. *
  5. * This work is licensed under the terms of MAME license.
  6. * See COPYING file in the top-level directory.
  7. */
  8. #include <stdio.h>
  9. #include <pico/pico_int.h>
  10. #define DR_MP3_IMPLEMENTATION
  11. #include "dr_libs/dr_mp3.h"
  12. #include "mp3.h"
  13. static drmp3dec mp3dec;
  14. static unsigned char mp3_input_buffer[2 * 1024];
  15. int mp3dec_start(FILE *f, int fpos_start)
  16. {
  17. drmp3dec_init(&mp3dec);
  18. return 0;
  19. }
  20. int mp3dec_decode(FILE *f, int *file_pos, int file_len)
  21. {
  22. drmp3dec_frame_info info;
  23. unsigned char *readPtr;
  24. int bytesLeft;
  25. int offset; // mp3 frame offset from readPtr
  26. int len;
  27. int retry = 3;
  28. do
  29. {
  30. if (*file_pos >= file_len)
  31. return 1; /* EOF, nothing to do */
  32. fseek(f, *file_pos, SEEK_SET);
  33. bytesLeft = fread(mp3_input_buffer, 1, sizeof(mp3_input_buffer), f);
  34. offset = mp3_find_sync_word(mp3_input_buffer, bytesLeft);
  35. if (offset < 0) {
  36. lprintf("find_sync_word (%i/%i) err %i\n",
  37. *file_pos, file_len, offset);
  38. *file_pos = file_len;
  39. return 1; // EOF
  40. }
  41. *file_pos += offset;
  42. readPtr = mp3_input_buffer + offset;
  43. bytesLeft -= offset;
  44. len = drmp3dec_decode_frame(&mp3dec, readPtr, bytesLeft, cdda_out_buffer, &info);
  45. if (len > 0) // retrieved decoded data
  46. *file_pos += info.frame_bytes;
  47. else if (info.frame_bytes > 0) // no output but input consumed?
  48. *file_pos += 1; // try to skip frame
  49. else if (offset == 0) // bad frame?
  50. *file_pos += 1; // try resyncing
  51. // else // truncated frame, try more data
  52. }
  53. while (len <= 0 && --retry > 0);
  54. return len <= 0;
  55. }