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65 lines
1.5 KiB
C
65 lines
1.5 KiB
C
/*
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* MP3 decoding using dr_mp3
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* (C) kub, 2020
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*
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* This work is licensed under the terms of MAME license.
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* See COPYING file in the top-level directory.
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*/
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#include <stdio.h>
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#include <pico/pico_int.h>
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#define DR_MP3_IMPLEMENTATION
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#include "dr_libs/dr_mp3.h"
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#include "mp3.h"
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static drmp3dec mp3dec;
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static unsigned char mp3_input_buffer[2 * 1024];
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int mp3dec_start(FILE *f, int fpos_start)
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{
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drmp3dec_init(&mp3dec);
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return 0;
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}
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int mp3dec_decode(FILE *f, int *file_pos, int file_len)
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{
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drmp3dec_frame_info info;
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unsigned char *readPtr;
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int bytesLeft;
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int offset; // mp3 frame offset from readPtr
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int len;
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int retry = 3;
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do
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{
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if (*file_pos >= file_len)
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return 1; /* EOF, nothing to do */
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fseek(f, *file_pos, SEEK_SET);
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bytesLeft = fread(mp3_input_buffer, 1, sizeof(mp3_input_buffer), f);
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offset = mp3_find_sync_word(mp3_input_buffer, bytesLeft);
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if (offset < 0) {
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lprintf("find_sync_word (%i/%i) err %i\n",
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*file_pos, file_len, offset);
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*file_pos = file_len;
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return 1; // EOF
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}
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*file_pos += offset;
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readPtr = mp3_input_buffer + offset;
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bytesLeft -= offset;
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len = drmp3dec_decode_frame(&mp3dec, readPtr, bytesLeft, cdda_out_buffer, &info);
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if (len > 0) // retrieved decoded data
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*file_pos += info.frame_bytes;
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else if (info.frame_bytes > 0) // no output but input consumed?
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*file_pos += 1; // try to skip frame
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else if (offset == 0) // bad frame?
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*file_pos += 1; // try resyncing
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// else // truncated frame, try more data
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}
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while (len <= 0 && --retry > 0);
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return len <= 0;
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}
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