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README.md
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README.md
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# MPEG-1 Layer III
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## the best audio format in fact
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### (it is true)
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# files
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- dat.h: miscellaneous tables and constants needed by the library
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- huffman.h: generated huffman table
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- main.c: test application for the library
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- mp3.c: library code
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- mp3.h: library header, include this in client code
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- scr: scripts unneeded to use the library, provided for reference purposes
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+ huff: wrapper for huffcvt, generating huffman tables copied to the clipboard from the mp3 specification
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+ scr/huffcvt.c: changes huffman string format to c array
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uint16_t l3_bitrates[16] = {0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0};
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uint16_t l3_smprates[4] = {44100, 48000, 32000, 0};
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// TODO possiblility block_type is undefined if blocksplit not set. read spec for blocksplit_flag and block_type
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// table to get length of scalefactor bands
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uint8_t sfcom[16][2] = {
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{0,0},
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{0,1},
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{0,2},
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{0,3},
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{3,0},
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{1,1},
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{1,2},
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{1,3},
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{2,1},
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{2,2},
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{2,3},
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{3,1},
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{3,2},
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{3,3},
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{4,2},
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{4,3},
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};
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uint8_t sf[3][33] = {
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{ // 32000hz band
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4,4,4,4,4,4,6,6,8,10,12,16,20,24,30,38,46,56,68,84,102,
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4,4,4,4,6,8,12,16,20,26,34,42
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}, { // 44100hz band
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4,4,4,4,4,4,6,6,8,8,10,12,16,20,24,28,34,42,50,54,76,
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4,4,4,4,6,8,10,12,14,18,22,30
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}, { // 48000hz band
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4,4,4,4,4,4,6,6,6,8,10,12,16,18,22,28,34,40,46,54,54,
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4,4,4,4,6,6,10,12,14,16,20,26
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}
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};
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uint8_t preemph[21] = {0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,3,3,3,2};
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long double alias[8] = {
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-.6,
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-.535,
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-.33,
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-.185,
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-.095,
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-.041,
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-.0142,
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-.0037
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};
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// Huffman code table for quadruples (A)
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// search by value
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uint8_t hquada[16] = {
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0b10000000,
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0b01010000,
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0b01000000,
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0b00101000,
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0b01100000,
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0b00010100,
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0b00100000,
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0b00010000,
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0b01110000,
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0b00011000,
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0b00110000,
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0b00000000,
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0b00111000,
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0b00001000,
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0b00001100,
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0b00000100,
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};
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// Huffman code table for quadruples (B)
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// What The Hell
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// search by index
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uint8_t hquadb[16] = {
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15,
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14,
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13,
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12,
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11,
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10,
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9,
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8,
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7,
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6,
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5,
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4,
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3,
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2,
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1,
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0
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};
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// first ESC table is 16
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char linbits[16] = {1, 2, 3, 4, 6, 8, 10, 13, 4, 5, 6, 7, 8, 9, 11, 13};
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#include "mp3.h"
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#include "huffman.h"
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#include "dat.h"
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// TODO autodetect endianness here
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#define fromle(x) (x)
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// get bit big endian
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//#define bitb(x, y) ((((uint8_t*)(x))[(y) >> 3] >> (7 - ((y) & 7))) & 1)
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uint8_t bitb(uint8_t* s, uint32_t b) {
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return (s[b >> 3] >> (7 - (b & 7))) & 1;
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}
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#define cast(x, y) (*((x*)&(y)))
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#define cblimit 21
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#define cblimit_short 12
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uint32_t ibitrb(uint8_t* s, uint32_t* b, char e) { // bit range big endian
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uint32_t a = 0;
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for(int i = 0; i < e; i++) a = (a << 1) | bitb(s, (*b)+i);
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//printf("bitrb %i at %i: 0x%X, 0d%u\n", e, *b, a, a);
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*b += e;
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return a;
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}
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uint32_t verify_l3(uint32_t d) { // returns 0 if header is valid
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d = ntohl(d);
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printf("magic %08X\n", d);
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//return (d & 0xFFF00000) ^ 0xFFF00000;
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return (d & 0xFFFE0000) ^ 0xFFFA0000;
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}
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void rdl3(uint32_t* s, mp3_frame* m) {
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uint32_t d = ntohl(*(s++));
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m->hdr = d;
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m->prot = (d >> 16) & 1;
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m->bitrate = l3_bitrates[(d >> 12) & 0xF];
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m->smprate = l3_smprates[(d >> 10) & 3];
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m->smpbit = (d >> 10) & 3;
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m->len = 144000 * m->bitrate / m->smprate + ((d >> 9) & 1);
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m->priv = (d >> 8) & 1;
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m->mode = (d >> 6) & 3;
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m->jmss = (d >> 5) & 1;
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m->jint = (d >> 4) & 1;
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m->emph = d & 3;
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m->crc = htons(*((uint16_t*)s)); // only valid if m->crc
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uint32_t bp = m->prot << 4; // bitpointer
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uint16_t main_data_end = bitrb(s, &bp, 9);
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char private_bits = bitrb(s, &bp, 5 - ((m->mode != 3) << 1));
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char num_ch = 1 + (m->mode != 3);
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char scfsi[4][num_ch];
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uint16_t part2_3_length[2][num_ch];
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uint16_t big_values[2][num_ch];
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uint8_t global_gain[2][num_ch];
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uint8_t scalefac_compress[2][num_ch];
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uint8_t blocksplit_flag[2][num_ch];
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// used if blocksplit flag is set
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uint8_t block_type[2][num_ch];
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uint8_t switch_point[2][num_ch];
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uint8_t table_select[2][2][num_ch];
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uint8_t subblock_gain[3][2][num_ch];
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// used if NOT set
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uint8_t region_address1[2][num_ch];
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uint8_t region_address2[2][num_ch];
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uint8_t preflag[2][num_ch];
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uint8_t scalefac_scale[2][num_ch];
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uint8_t count1table_select[2][num_ch];
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for(int band = 0; band < 4; band++) for(int ch = 0; ch < num_ch; ch++) scfsi[band][ch] = bitrb(s, &bp, 1);
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for(int gr = 0; gr < 2; gr++) for(int ch = 0; ch < num_ch; ch++) {
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part2_3_length[gr][ch] = bitrb(s, &bp, 12);
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big_values[gr][ch] = bitrb(s, &bp, 9);
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global_gain[gr][ch] = bitrb(s, &bp, 8);
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scalefac_compress[gr][ch] = bitrb(s, &bp, 4);
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blocksplit_flag[gr][ch] = bitrb(s, &bp, 1);
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if(blocksplit_flag[gr][ch]) {
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block_type[gr][ch] = bitrb(s, &bp, 2);
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switch_point[gr][ch] = bitrb(s, &bp, 1);
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for(int reg = 0; reg < 2; reg++) table_select[reg][gr][ch] = bitrb(s, &bp, 5);
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for(int window = 0; window < 3; window++) subblock_gain[window][gr][ch] = bitrb(s, &bp, 3);
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} else {
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for(int reg = 0; reg < 3; reg++) table_select[reg][gr][ch] = bitrb(s, &bp, 5);
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region_address1[gr][ch] = bitrb(s, &bp, 4);
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region_address2[gr][ch] = bitrb(s, &bp, 3);
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}
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preflag[gr][ch] = bitrb(s, &bp, 1);
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scalefac_scale[gr][ch] = bitrb(s, &bp, 1);
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count1table_select[gr][ch] = bitrb(s, &bp, 1);
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}
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// begin to parse main_data
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// TODO completely unclear where it is supposed to start - comment from specification reproduced below
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/***
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The main_data follows. It does not follow the above side information in the
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bitstream. The main_data ends at a location in the main_data bitstream
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preceding the frame header of the following frame at an offset given by the
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value of main_data_end (see definition of main_data_end and 3-Annex Fig.3-
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A.7.1
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***/
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int bpsave = bp;
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for(int gr = 0; gr < 2; gr++) for(int ch = 0; ch < num_ch; ch++) {
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if(blocksplit_flag[gr][ch] && block_type[gr][ch] == 2) {
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// long window(?)
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for(int cb = 0; cb < (switch_point[gr][ch] ? 8 : 0); cb++) if(!scfsi[cb] | !gr) {
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// TODO scalefac[cb][gr][ch]
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// use scalefac_compress[gr][ch]
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int sfcd;
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if(block_type[gr][ch] != 2) sfcd = cb > 10;
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else if(switch_point[gr][ch]) {
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// TODO if block_type is 2 and switch_point is 1
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} else sfcd = cb > 5;
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//scalefac[cb][0/*window*/][gr][ch] = bitrb(s, &bp, sfcom[scalefac_compress[gr][ch]][sfcd]);
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}
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// short window(?)
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for(int cb = (switch_point[gr][ch] ? 3 : 0); cb < cblimit_short; cb++) for(int window = 0; window < 3; window++) if(!scfsi[cb] | !gr) {
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// TODO scalefac[cb][gr][ch]
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// use scalefac_compress[gr][ch]
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}
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} else {
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for(int cb = 0; cb < cblimit; cb++) if(!scfsi[cb] | !gr) {
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// TODO scalefac[cb][gr][ch]
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// use scalefac_compress[gr][ch]
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}
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// TODO huffman bits
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unsigned short csz = 16, ci = 0;
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coord* c = malloc(csz * sizeof(coord));
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while(bp < bpsave + part2_3_length[gr][ch]) {
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//bp += huffman(table_select[]);
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}
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}
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}
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}
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#include <stdint.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <arpa/inet.h>
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#define bitrb(x, y, z) ibitrb((uint8_t*)x, y, z)
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typedef struct {
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uint8_t x;
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uint8_t y;
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} coord;
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// frame data
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typedef struct {
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uint32_t hdr;
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// parsed out
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uint16_t bitrate;
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uint16_t smprate;
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uint16_t len;
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// bitflags
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uint8_t prot; // crc protection - TODO add to verify_l3
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uint8_t priv;
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uint8_t smpbit;
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uint8_t jint; // joint stereo - intensity stereo
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uint8_t jmss; // joint stereo - MS stereo (?)
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// indices
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uint8_t mode;
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uint8_t emph; // emphasis?
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// parsed data
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int32_t crc; // negative when not present
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uint8_t dat[1018];
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} mp3_frame;
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uint8_t bitb(uint8_t* s, uint32_t b);
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uint32_t ibitrb(uint8_t* s, uint32_t* b, char e);
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uint32_t verify_l3(uint32_t d);
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void rdl3(uint32_t* s, mp3_frame* m);
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echo -e ", {\t\t\t\t\t\t\t// $1"
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eval `wl-paste|sed 's/^/\.\/huffcvt /g;s/$/;/g'`
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echo -ne '\t}'
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#include <string.h>
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#include <stdio.h>
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unsigned long btoi(char* s) {
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unsigned long r = 0;
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int l = strlen(s) - 1;
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for(int i = l; i >= 0; i--) {
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r <<= 1;
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r |= (s[l-i]-'0');
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}
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return r;
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}
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int main(int argc, char** argv) {
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printf("\t\t{%s,%s,%s,%i},\n", argv[1], argv[2], argv[3], btoi(argv[4]));
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}
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