progress

main.c

@@ -1,19 +1,33 @@
 #include <stdint.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <string.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <arpa/inet.h>
 
+// TODO autodetect endianness here
+#define fromle(x) (x)
+
 // get bit big endian
-#define bitb(x, y) ((((uint8_t*)(x))[y >> 3] >> (7 - (y & 7))) & 1)
+//#define bitb(x, y) ((((uint8_t*)(x))[(y) >> 3] >> (7 - ((y) & 7))) & 1)
+
+uint8_t bitb(uint8_t* s, uint32_t b) {
+	return (s[b >> 3] >> (7 - (b & 7))) & 1;
+}
+
+#define bitrb(x, y, z) ibitrb((uint8_t*)x, y, z)
 #define cast(x, y) (*((x*)&(y)))
 
-uint32_t bitrb(uint8_t* s, uint32_t b, char e) { // bit range big endian
+#define cblimit 21
+#define cblimit_short 12
+
+uint32_t ibitrb(uint8_t* s, uint32_t* b, char e) { // bit range big endian
 	uint32_t a = 0;
-	for(int i = 0; i < e; i++) a = (a << 1) | bitb(s, b+i);
+	for(int i = 0; i < e; i++) a = (a << 1) | bitb(s, (*b)+i);
-	printf("bitrb %X\n", a);
+	//printf("bitrb %i at %i: 0x%X, 0d%u\n", e, *b, a, a);
+	*b += e;
 	return a;
 }
 
@@ -5127,6 +5141,32 @@ uint32_t verify_l3(uint32_t d) { // returns 0 if header is valid
 	return (d & 0xFFFE0000) ^ 0xFFFA0000;
 }
 
+typedef struct {
+	uint8_t x;
+	uint8_t y;
+} coord;
+
+// TODO possiblility block_type is undefined if blocksplit not set. read spec for blocksplit_flag and block_type
+// table to get length of scalefactor bands
+uint8_t sfcom[16][2] = {
+	{0,0},
+	{0,1},
+	{0,2},
+	{0,3},
+	{3,0},
+	{1,1},
+	{1,2},
+	{1,3},
+	{2,1},
+	{2,2},
+	{2,3},
+	{3,1},
+	{3,2},
+	{3,3},
+	{4,2},
+	{4,3},
+};
+
 void rdl3(uint32_t* s, mp3_frame* m) {
 	uint32_t d = ntohl(*(s++));
 	m->hdr = d;
@@ -5143,9 +5183,98 @@ void rdl3(uint32_t* s, mp3_frame* m) {
 
 	m->crc = htons(*((uint16_t*)s)); // only valid if m->crc
 	
-	int bp = m->prot << 4; // bitpointer
+	uint32_t bp = m->prot << 4; // bitpointer
-	if(m->mode) { // mono
+	
-		
+	uint16_t main_data_end = bitrb(s, &bp, 9);
+	char private_bits = bitrb(s, &bp, 5 - ((m->mode != 3) << 1));
+	char num_ch = 1 + (m->mode != 3);
+	char scfsi[4][num_ch];
+	uint16_t part2_3_length[2][num_ch];
+	uint16_t big_values[2][num_ch];
+	uint8_t global_gain[2][num_ch];
+	uint8_t scalefac_compress[2][num_ch];
+	uint8_t blocksplit_flag[2][num_ch];
+
+	// used if blocksplit flag is set
+	uint8_t block_type[2][num_ch];
+	uint8_t switch_point[2][num_ch];
+	uint8_t table_select[2][2][num_ch];
+	uint8_t subblock_gain[3][2][num_ch];
+
+	// used if NOT set
+	uint8_t region_address1[2][num_ch];
+	uint8_t region_address2[2][num_ch];
+
+	uint8_t preflag[2][num_ch];
+	uint8_t scalefac_scale[2][num_ch];
+	uint8_t count1table_select[2][num_ch];
+
+	for(int band = 0; band < 4; band++) for(int ch = 0; ch < num_ch; ch++) scfsi[band][ch] = bitrb(s, &bp, 1);
+	
+	for(int gr = 0; gr < 2; gr++) for(int ch = 0; ch < num_ch; ch++) {
+		part2_3_length[gr][ch] = bitrb(s, &bp, 12);
+		big_values[gr][ch] = bitrb(s, &bp, 9);
+		global_gain[gr][ch] = bitrb(s, &bp, 8);
+		scalefac_compress[gr][ch] = bitrb(s, &bp, 4);
+		blocksplit_flag[gr][ch] = bitrb(s, &bp, 1);
+		if(blocksplit_flag[gr][ch]) {
+			block_type[gr][ch] = bitrb(s, &bp, 2);
+			switch_point[gr][ch] = bitrb(s, &bp, 1);
+			for(int reg = 0; reg < 2; reg++) table_select[reg][gr][ch] = bitrb(s, &bp, 5);
+			for(int window = 0; window < 3; window++) subblock_gain[window][gr][ch] = bitrb(s, &bp, 3);
+		} else {
+			for(int reg = 0; reg < 3; reg++) table_select[reg][gr][ch] = bitrb(s, &bp, 5);
+			region_address1[gr][ch] = bitrb(s, &bp, 4);
+			region_address2[gr][ch] = bitrb(s, &bp, 3);
+		}
+		preflag[gr][ch] = bitrb(s, &bp, 1);
+		scalefac_scale[gr][ch] = bitrb(s, &bp, 1);
+		count1table_select[gr][ch] = bitrb(s, &bp, 1);
+	}
+
+	// begin to parse main_data
+	// TODO completely unclear where it is supposed to start - comment from specification reproduced below
+	/***
+		The main_data follows. It does not follow the above side information in the
+		bitstream. The main_data ends at a location in the main_data bitstream
+		preceding the frame header of the following frame at an offset given by the
+		value of main_data_end (see definition of main_data_end and 3-Annex Fig.3-
+		A.7.1
+	***/
+	
+	int bpsave = bp;
+
+	for(int gr = 0; gr < 2; gr++) for(int ch = 0; ch < num_ch; ch++) {
+		if(blocksplit_flag[gr][ch] && block_type[gr][ch] == 2) {
+			// long window(?)
+			for(int cb = 0; cb < (switch_point[gr][ch] ? 8 : 0); cb++) if(!scfsi[cb] | !gr) {
+				// TODO scalefac[cb][gr][ch]
+				// use scalefac_compress[gr][ch]
+				int sfcd;
+				if(block_type[gr][ch] != 2) sfcd = cb > 10;
+				else if(switch_point[gr][ch]) {
+					// TODO if block_type is 2 and switch_point is 1
+				} else sfcd = cb > 5;
+				//scalefac[cb][0/*window*/][gr][ch] = bitrb(s, &bp, sfcom[scalefac_compress[gr][ch]][sfcd]);
+
+			}
+			// short window(?)
+			for(int cb = (switch_point[gr][ch] ? 3 : 0); cb < cblimit_short; cb++) for(int window = 0; window < 3; window++) if(!scfsi[cb] | !gr) {
+				// TODO scalefac[cb][gr][ch]
+				// use scalefac_compress[gr][ch]
+			}
+		} else {
+			for(int cb = 0; cb < cblimit; cb++) if(!scfsi[cb] | !gr) {
+				// TODO scalefac[cb][gr][ch]
+				// use scalefac_compress[gr][ch]
+			}
+			// TODO huffman bits
+			unsigned short csz = 16, ci = 0;
+			coord* c = malloc(csz * sizeof(coord));
+			while(bp < bpsave + part2_3_length[gr][ch]) {
+				//bp += huffman(table_select[]);
+			}
+		}
 	}
 }
 
@@ -5164,11 +5293,20 @@ int main(int argc, char** argv) {
 		uint8_t* stream = malloc(s.st_size);
 		read(fd, stream, s.st_size);
 
+
 		static char* yn[2] = {"no", "yes"};
 		static char* chtyp[4] = {"stereo", "joint stereo", "dual mono (stereo)", "mono"};
 		static char* emph[4] = {"none", "50/15 ms", "reserved", "CCIT J.17"};
 
-		printf("begin reading %s (%u bytes at %p)\n", argv[f], s.st_size, stream);
+		printf("begin reading %s (%lu bytes at %p)\n", argv[f], s.st_size, stream);
+
+		if(!memcmp(stream, "ID3", 3)) {
+			int d = htonl(*((uint32_t*)(stream + 6)));
+			sp += d + 10 + ((stream[5] & 0x10) ? 10 : 0);
+			printf("ID3v2 detected, skipping %08X bytes so as not to deal with it\n", sp);
+		}
+
+		if(!memcmp(stream + s.st_size - 128, "TAG", 3)) printf("TAG detected :)\n");
 
 		while(!verify_l3(*(uint32_t*)(stream + sp))) {
 			printf("frame %u sync at %u (%X)!\n", fc, sp, sp);
@@ -5196,5 +5334,7 @@ int main(int argc, char** argv) {
 			sp += m.len;
 			fc++;
 		}
+
+		free(stream);
 	}
 }