Finding first audio frame in a MP3 file

// XXX: Find the first sync

uint32\_t id3\_bytes\_read = 0;

uint8\_t id3\_buffer\[2881\] = {0};

uint32\_t last\_file\_location = 0;

uint32\_t current\_file\_location = 0;

ptrdiff\_t diff = 0;


do {

last_file_location = f_tell(&track);

// XXX: Get a chunk of data from the SD card

retSD = f_read(&track, id3_buffer, 1024, (UINT *) &id3_bytes_read);

if (FR_OK != retSD) {

FatFsError(retSD);

    }

// XXX: Set the read data as mad stream

    mad\_stream\_buffer(&id3\_stream, (unsigned char const \*) id3\_buffer, sizeof id3\_buffer);

// XXX: Try to decode it, TODO: check return

    mad\_frame\_decode(&id3\_frame, &id3\_stream);

// XXX: Try to find a SYNC flag

    if (0 == mad\_stream\_sync(&id3\_stream)) {

diff = id3_stream.this_frame - id3_buffer;

break;

    }

    HAL\_Delay(25);

} while (1);


current_file_location = f_tell(&track);

DBG_println("We're at 0x%X", current_file_location);

DBG_println("Diff: 0x%X (%d)", current_file_location - (last_file_location + diff), current_file_location - (last_file_location + diff));

// XXX: Go back N bytes so from now on we read data from the location of the first SYNC flag

retSD = f_lseek(&track, current_file_location - (current_file_location - last_file_location + diff));


// XXX: We're done

mad_stream_finish(&id3_stream);

mad_frame_finish(&id3_frame);