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MP3 additions
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Specify ID3 version
Add MP3 L1/L2 band info
Add MP3 ID3v1 support
Add MP3 emphasis
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@dd86k
dd86k committed Jun 3, 2019
1 parent 5758c17 commit 3fa6c6b
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Showing 3 changed files with 81 additions and 38 deletions.
99 changes: 65 additions & 34 deletions src/audio/mp3.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,40 +4,42 @@
#include "../utils.h"
#include "mp3.h"

// MPEG-1 ISO/IEC 11172-3
// MPEG-2 ISO/IEC 13818-3
// MPEG-1: ISO/IEC 11172-3
// MPEG-2: ISO/IEC 13818-3
// ID3v1: http://www.mpgedit.org/mpgedit/mpeg%5Fformat/mpeghdr.htm
// ID3V2: http://id3.org/

void scan_mp3(uint32_t sig, int id3) {
char bv1l1[][8] = {
char bv1l1[16][8] = {
"free", "32", "64", "96", "128", "160", "192", "224",
"256", "288", "320", "352", "384", "416", "448", "bad"
};
char bv1l2[][8] = {
char bv1l2[16][8] = {
"free", "32", "48", "56", "64", "80", "96", "112",
"128", "160", "192", "224", "256", "320", "384", "bad"
};
char bv1l3[][8] = {
char bv1l3[16][8] = {
"free", "32", "40", "48", "56", "64", "80", "96",
"112", "128", "160", "192", "224", "256", "320", "bad"
};
char bv2l1[][8] = {
char bv2l1[16][8] = {
"free", "32", "48", "56", "64", "80", "96", "112",
"128", "144", "160", "176", "192", "224", "256", "bad"
};
char bv2l23[][8] = {
char bv2l23[16][8] = {
"free", "8", "16", "24", "32", "40", "48", "56",
"64", "80", "96", "112", "128", "144", "160", "bad"
};
char fv1[][8] = {
char fv1[4][8] = {
"44100", "48000", "32000", "(res.)"
};
char fv2[][8] = {
char fv2[4][8] = {
"22050", "24000", "16000", "(res.)"
};
/*char fv25[][8] = {
/*char fv25[4][8] = {
"11025", "12000", "8000", "(res.)"
};*/
char ca[][8] = {
char ca[4][8] = {
"stereo", "joint", "dual", "mono"
};

Expand All @@ -51,23 +53,26 @@ void scan_mp3(uint32_t sig, int id3) {
size_t bi = h.info >> 4; // bitrate index
size_t fi = (h.info >> 2) & 3; // frequency index
size_t ci = (h.extra >> 6); // channel index
char li; // layer index, only for mode extension

switch (h.sig & 0x600) {
case 0x200:
li = 3;
l = "III";
b = v == '2' ? bv2l23[bi] : bv1l3[bi];
break;
case 0x400:
li = 2;
l = "II";
b = v == '2' ? bv2l23[bi] : bv1l2[bi];
break;
case 0x600:
li = 1;
l = "I";
b = v == '2' ? bv2l1[bi] : bv1l1[bi];
break;
default:
l = "(res.)";
b = "(res.)";
li = 0; l = "(res.)"; b = "(res.)";
break;
}
f = v == '2' ? fv2[fi] : fv1[fi];
Expand All @@ -77,52 +82,78 @@ void scan_mp3(uint32_t sig, int id3) {
"MPEG-%c Audio Layer %s (MP3) audio, %s Hz, %s kbps, %s",
v, l, f, b, c
);
if (ci == 1) { // joint stereo audio
if (h.extra & 0x20)
printf(" +intensity");
if (h.extra & 0x10)
printf(" +ms");
if (ci == 1) { // joint stereo audio, regardless of version
switch (li) { // layer
case 3:
if (h.extra & 0x20)
printf(" +intensity");
if (h.extra & 0x10)
printf(" +ms");
break;
case 2: case 1:
switch (h.extra & 0x30) {
case 0: printf(" (band 4-31)"); break;
case 0x10: printf(" (band 8-31)"); break;
case 0x20: printf(" (band 12-31)"); break;
case 0x30: printf(" (band 16-31)"); break;
}
break;
}
}
switch (id3) {
case 2: printf(", id3v2"); break;
case 1: printf(", id3v1"); break;
}
if (id3)
printf(", id3");
if (h.sig & 0x100)
printf(", crc16");
if (h.info & 1)
printf(", priv. bit");
printf(", pbit");
if (h.info & 2)
printf(", pad");
if (h.extra & 8)
printf(", copyright");
if (h.extra & 6)
printf(", original");
switch (h.extra & 3) {
case 1: printf(", 50/15 ms\n"); return;
case 3: printf(", CCIT J.17\n"); return;
}
putchar('\n');
}

// returns non-zero if 4-byte sig is mp3, LSB only
int check_mp3(uint32_t s) {
return (bswap16(s) >> 4) == 0xFFF;
}

// skip id3 and return signature
int skip_id3() {
struct id3_hdr h;
_ddseek(0, SEEK_SET);
// skip ID3v2 header, assuming we're already 4 bytes within file (file pointer
// being at position byte 3), and return signature after id3
int skip_id3v2() {
struct id3_hdr_p h;
_ddread(&h, sizeof(h));
// Synchsafe integers
// Yep, every 7th bit is not used, on top of being MSB
// So the entire integer is spread out like so: 0xxxxxxx 0xxxxxxx
// Synchsafe integers: only bits 0-6 are used (0xxxxxxx 0xxxxxxx)
// Also if footer present, +20 instead of +10 for size
int ns = (h.sizea[0] << 21 | h.sizea[1] << 14 |
h.sizea[2] << 7 | h.sizea[3]) +
(h.flags & 0x10 ? 20 : 10);
if (_ddseek(ns, SEEK_SET)) {
report_data();
if (_ddseek(ns, SEEK_SET)) goto ID3_END;
uint32_t s;
_ddread(&s, 4);
if (check_mp3(s) == 0) {
ID3_END: report_data();
exit(0);
}
return s;
}

// skip IDv1 header, and return signature after id3
int skip_id3v1() {
if (_ddseek(128, SEEK_SET)) goto ID3_END;
uint32_t s;
_ddread(&s, 4);
/*if (check_mp3(s)) {
report_data();
if (check_mp3(s) == 0) {
ID3_END: report_data();
exit(0);
}*/
return s; // don't ask me why
}
return s;
}
12 changes: 11 additions & 1 deletion src/audio/mp3.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,15 @@ struct id3_hdr {
};
};

struct id3_hdr_p { // Partial, no sig and majorver
uint8_t ver;
uint8_t flags;
union {
uint32_t size; // Synchsafe integer
uint8_t sizea[4];
};
};

/*struct id3_frame_hdr {
uint32_t id; // frame id
uint32_t size;
Expand All @@ -22,4 +31,5 @@ struct id3_hdr {

void scan_mp3(uint32_t, int);
int check_mp3(uint32_t);
int skip_id3(void);
int skip_id3v1(void);
int skip_id3v2(void);
8 changes: 5 additions & 3 deletions src/ff.c
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Original file line number Diff line number Diff line change
Expand Up @@ -592,11 +592,13 @@ WAD: { // Fixes "expression expected" on clang-alpine
case 0x0184CF:
report("Lepton-compressed JPEG image (LEP)");
return;

//case 0xNNNNNN: // "TAG", big-endian, ID3v1

case 0x474154: // "TAG", big-endian, ID3v1
scan_mp3(skip_id3v1(), 1);
return;

case 0x334449: // "ID3", big-endian, ID3v2
scan_mp3(skip_id3(), 1);
scan_mp3(skip_id3v2(), 2);
return;

default:
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