Jeff Epler
afe0e5fb5a
The standalone decoder can be built on Linux with "make" and the files it creates can be played with "aplay -c2 -r 44100 -f S16_LE"
98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
#include <stdio.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "mp3dec.h"
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#define MAX_BUFFER_LEN (MAX_NSAMP * MAX_NGRAN * MAX_NCHAN)
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int16_t audiodata[MAX_BUFFER_LEN];
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typedef struct {
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char *ptr, *end;
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} stream;
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#define READ_PTR(stream) ((void*)((stream)->ptr))
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#define BYTES_LEFT(stream) ((stream)->end - (stream)->ptr)
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#define CONSUME(stream, n) ((stream)->ptr += n)
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void skip_id3v2(stream* self) {
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if (BYTES_LEFT(self) < 10) {
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return;
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}
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uint8_t *data = READ_PTR(self);
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if (!(
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data[0] == 'I' &&
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data[1] == 'D' &&
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data[2] == '3' &&
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data[3] != 0xff &&
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data[4] != 0xff &&
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(data[5] & 0x1f) == 0 &&
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(data[6] & 0x80) == 0 &&
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(data[7] & 0x80) == 0 &&
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(data[8] & 0x80) == 0 &&
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(data[9] & 0x80) == 0)) {
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return;
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}
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uint32_t size = (data[6] << 21) | (data[7] << 14) | (data[8] << 7) | (data[9]);
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size += 10; // size excludes the "header" (but not the "extended header")
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CONSUME(self, size + 10);
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}
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bool mp3file_find_sync_word(stream* self) {
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int offset = MP3FindSyncWord(READ_PTR(self), BYTES_LEFT(self));
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if (offset >= 0) {
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CONSUME(self, offset);
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return true;
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}
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return false;
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}
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void fatal(const char *msg) { fprintf(stderr, "%s\n", msg); exit(1); }
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void perror_fatal(const char *msg) { perror(msg); exit(1); }
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int main(int argc, char **argv) {
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if(argc != 3) {
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fprintf(stderr, "Decode MP3 into headerless LE16 stereo\n");
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fprintf(stderr, "Usage: %s input.mp3 output.bin\n", argv[0]);
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exit(99);
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}
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HMP3Decoder decoder = MP3InitDecoder();
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FILE *fi = fopen(argv[1], "rb");
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if(!fi) perror_fatal("open");
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struct stat st;
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if(fstat(fileno(fi), &st) < 0) perror_fatal("fstat");
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stream s;
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s.ptr = malloc(st.st_size);
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if(!s.ptr) perror_fatal("malloc");
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s.end = s.ptr + st.st_size;
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if(fread(s.ptr, 1, st.st_size, fi) != st.st_size) perror_fatal("fread");
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FILE *fo = fopen(argv[2], "wb");
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if(!fo) perror_fatal("open");
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skip_id3v2(&s);
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while(mp3file_find_sync_word(&s)) {
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MP3FrameInfo fi;
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int err = MP3GetNextFrameInfo(decoder, &fi, READ_PTR(&s));
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if(err != ERR_MP3_NONE) fatal("MP3GetNextFrameInfo");
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int bytes_left = (int)BYTES_LEFT(&s);
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uint8_t *inbuf = READ_PTR(&s);
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err = MP3Decode(decoder, &inbuf, &bytes_left,
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audiodata, 0);
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if(err != ERR_MP3_NONE) fatal("MP3Decode");
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if(fwrite(audiodata, 1, fi.outputSamps*sizeof(int16_t), fo)
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!= fi.outputSamps*sizeof(int16_t))
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perror_fatal("fwrite");
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CONSUME(&s, BYTES_LEFT(&s) - bytes_left);
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}
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return 0;
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}
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