Beard at 16:50, 26 July 2019

2019-07-26T16:50:21Z

Beard at 16:46, 26 July 2019

2019-07-26T16:46:31Z

Beard at 19:38, 8 May 2018

2018-05-08T19:38:58Z

New page

This program decodes a compressed .ecm file. Code obtained from http://www.stramaxon.com/2012/04/how-to-convert-ecm-file-to-bin.html. I've confirmed it works.

Copy the source code below to a file <code>unecm.c</code>.

Now Compile it:

<pre>
gcc -o unecm unecm.c
</pre>

After you've compiled it, run it like this:
<pre>
./unecm filename.img.ecm
</pre>

The uncompressed image file is now called <code>filename.img.ecm</code> in the same folder as the original.

<b>Source code:</b>
<syntaxhighlight lang="c">

/***************************************************************************/
/*
** UNECM - Decoder for ECM (Error Code Modeler) format.
** Version 1.0
** Copyright (C) 2002 Neill Corlett
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the GNU General Public License
** as published by the Free Software Foundation; either version 2
** of the License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/***************************************************************************/
/*
** Portability notes:
**
** - Assumes a 32-bit or higher integer size
** - No assumptions about byte order
** - No assumptions about struct packing
** - No unaligned memory access
*/
/***************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/***************************************************************************/

void banner(void) {
fprintf(stderr,
"UNECM - Decoder for Error Code Modeler format v1.0\n"
"Copyright (C) 2002 Neill Corlett\n\n"
);
}

/***************************************************************************/

/* Data types */
#define ecc_uint8 unsigned char
#define ecc_uint16 unsigned short
#define ecc_uint32 unsigned

/* LUTs used for computing ECC/EDC */
static ecc_uint8 ecc_f_lut[256];
static ecc_uint8 ecc_b_lut[256];
static ecc_uint32 edc_lut[256];

/* Init routine */
static void eccedc_init(void) {
ecc_uint32 i, j, edc;
for(i = 0; i < 256; i++) {
j = (i << 1) ^ (i & 0x80 ? 0x11D : 0);
ecc_f_lut[i] = j;
ecc_b_lut[i ^ j] = i;
edc = i;
for(j = 0; j < 8; j++) edc = (edc >> 1) ^ (edc & 1 ? 0xD8018001 : 0);
edc_lut[i] = edc;
}
}

/***************************************************************************/
/*
** Compute EDC for a block
*/
ecc_uint32 edc_partial_computeblock(
ecc_uint32 edc,
const ecc_uint8 *src,
ecc_uint16 size
) {
while(size--) edc = (edc >> 8) ^ edc_lut[(edc ^ (*src++)) & 0xFF];
return edc;
}

void edc_computeblock(
const ecc_uint8 *src,
ecc_uint16 size,
ecc_uint8 *dest
) {
ecc_uint32 edc = edc_partial_computeblock(0, src, size);
dest[0] = (edc >> 0) & 0xFF;
dest[1] = (edc >> 8) & 0xFF;
dest[2] = (edc >> 16) & 0xFF;
dest[3] = (edc >> 24) & 0xFF;
}

/***************************************************************************/
/*
** Compute ECC for a block (can do either P or Q)
*/
static void ecc_computeblock(
ecc_uint8 *src,
ecc_uint32 major_count,
ecc_uint32 minor_count,
ecc_uint32 major_mult,
ecc_uint32 minor_inc,
ecc_uint8 *dest
) {
ecc_uint32 size = major_count * minor_count;
ecc_uint32 major, minor;
for(major = 0; major < major_count; major++) {
ecc_uint32 index = (major >> 1) * major_mult + (major & 1);
ecc_uint8 ecc_a = 0;
ecc_uint8 ecc_b = 0;
for(minor = 0; minor < minor_count; minor++) {
ecc_uint8 temp = src[index];
index += minor_inc;
if(index >= size) index -= size;
ecc_a ^= temp;
ecc_b ^= temp;
ecc_a = ecc_f_lut[ecc_a];
}
ecc_a = ecc_b_lut[ecc_f_lut[ecc_a] ^ ecc_b];
dest[major ] = ecc_a;
dest[major + major_count] = ecc_a ^ ecc_b;
}
}

/*
** Generate ECC P and Q codes for a block
*/
static void ecc_generate(
ecc_uint8 *sector,
int zeroaddress
) {
ecc_uint8 address[4], i;
/* Save the address and zero it out */
if(zeroaddress) for(i = 0; i < 4; i++) {
address[i] = sector[12 + i];
sector[12 + i] = 0;
}
/* Compute ECC P code */
ecc_computeblock(sector + 0xC, 86, 24, 2, 86, sector + 0x81C);
/* Compute ECC Q code */
ecc_computeblock(sector + 0xC, 52, 43, 86, 88, sector + 0x8C8);
/* Restore the address */
if(zeroaddress) for(i = 0; i < 4; i++) sector[12 + i] = address[i];
}

/***************************************************************************/
/*
** Generate ECC/EDC information for a sector (must be 2352 = 0x930 bytes)
** Returns 0 on success
*/
void eccedc_generate(ecc_uint8 *sector, int type) {
ecc_uint32 i;
switch(type) {
case 1: /* Mode 1 */
/* Compute EDC */
edc_computeblock(sector + 0x00, 0x810, sector + 0x810);
/* Write out zero bytes */
for(i = 0; i < 8; i++) sector[0x814 + i] = 0;
/* Generate ECC P/Q codes */
ecc_generate(sector, 0);
break;
case 2: /* Mode 2 form 1 */
/* Compute EDC */
edc_computeblock(sector + 0x10, 0x808, sector + 0x818);
/* Generate ECC P/Q codes */
ecc_generate(sector, 1);
break;
case 3: /* Mode 2 form 2 */
/* Compute EDC */
edc_computeblock(sector + 0x10, 0x91C, sector + 0x92C);
break;
}
}

/***************************************************************************/

unsigned mycounter;
unsigned mycounter_total;

void resetcounter(unsigned total) {
mycounter = 0;
mycounter_total = total;
}

void setcounter(unsigned n) {
if((n >> 20) != (mycounter >> 20)) {
unsigned a = (n+64)/128;
unsigned d = (mycounter_total+64)/128;
if(!d) d = 1;
fprintf(stderr, "Decoding (%02d%%)\r", (100*a) / d);
}
mycounter = n;
}

int unecmify(
FILE *in,
FILE *out
) {
unsigned checkedc = 0;
unsigned char sector[2352];
unsigned type;
unsigned num;
fseek(in, 0, SEEK_END);
resetcounter(ftell(in));
fseek(in, 0, SEEK_SET);
if(
(fgetc(in) != 'E') ||
(fgetc(in) != 'C') ||
(fgetc(in) != 'M') ||
(fgetc(in) != 0x00)
) {
fprintf(stderr, "Header not found!\n");
goto corrupt;
}
for(;;) {
int c = fgetc(in);
int bits = 5;
if(c == EOF) goto uneof;
type = c & 3;
num = (c >> 2) & 0x1F;
while(c & 0x80) {
c = fgetc(in);
if(c == EOF) goto uneof;
num |= ((unsigned)(c & 0x7F)) << bits;
bits += 7;
}
if(num == 0xFFFFFFFF) break;
num++;
if(num >= 0x80000000) goto corrupt;
if(!type) {
while(num) {
int b = num;
if(b > 2352) b = 2352;
if(fread(sector, 1, b, in) != b) goto uneof;
checkedc = edc_partial_computeblock(checkedc, sector, b);
fwrite(sector, 1, b, out);
num -= b;
setcounter(ftell(in));
}
} else {
while(num--) {
memset(sector, 0, sizeof(sector));
memset(sector + 1, 0xFF, 10);
switch(type) {
case 1:
sector[0x0F] = 0x01;
if(fread(sector + 0x00C, 1, 0x003, in) != 0x003) goto uneof;
if(fread(sector + 0x010, 1, 0x800, in) != 0x800) goto uneof;
eccedc_generate(sector, 1);
checkedc = edc_partial_computeblock(checkedc, sector, 2352);
fwrite(sector, 2352, 1, out);
setcounter(ftell(in));
break;
case 2:
sector[0x0F] = 0x02;
if(fread(sector + 0x014, 1, 0x804, in) != 0x804) goto uneof;
sector[0x10] = sector[0x14];
sector[0x11] = sector[0x15];
sector[0x12] = sector[0x16];
sector[0x13] = sector[0x17];
eccedc_generate(sector, 2);
checkedc = edc_partial_computeblock(checkedc, sector + 0x10, 2336);
fwrite(sector + 0x10, 2336, 1, out);
setcounter(ftell(in));
break;
case 3:
sector[0x0F] = 0x02;
if(fread(sector + 0x014, 1, 0x918, in) != 0x918) goto uneof;
sector[0x10] = sector[0x14];
sector[0x11] = sector[0x15];
sector[0x12] = sector[0x16];
sector[0x13] = sector[0x17];
eccedc_generate(sector, 3);
checkedc = edc_partial_computeblock(checkedc, sector + 0x10, 2336);
fwrite(sector + 0x10, 2336, 1, out);
setcounter(ftell(in));
break;
}
}
}
}
if(fread(sector, 1, 4, in) != 4) goto uneof;
fprintf(stderr, "Decoded %ld bytes -> %ld bytes\n", ftell(in), ftell(out));
if(
(sector[0] != ((checkedc >> 0) & 0xFF)) ||
(sector[1] != ((checkedc >> 8) & 0xFF)) ||
(sector[2] != ((checkedc >> 16) & 0xFF)) ||
(sector[3] != ((checkedc >> 24) & 0xFF))
) {
fprintf(stderr, "EDC error (%08X, should be %02X%02X%02X%02X)\n",
checkedc,
sector[3],
sector[2],
sector[1],
sector[0]
);
goto corrupt;
}
fprintf(stderr, "Done; file is OK\n");
return 0;
uneof:
fprintf(stderr, "Unexpected EOF!\n");
corrupt:
fprintf(stderr, "Corrupt ECM file!\n");
return 1;
}

/***************************************************************************/

int main(int argc, char **argv) {
FILE *fin, *fout;
char *infilename;
char *outfilename;
banner();
/*
** Initialize the ECC/EDC tables
*/
eccedc_init();
/*
** Check command line
*/
if((argc != 2) && (argc != 3)) {
fprintf(stderr, "usage: %s ecmfile [outputfile]\n", argv[0]);
return 1;
}
/*
** Verify that the input filename is valid
*/
infilename = argv[1];
if(strlen(infilename) < 5) {
fprintf(stderr, "filename '%s' is too short\n", infilename);
return 1;
}
if(strcasecmp(infilename + strlen(infilename) - 4, ".ecm")) {
fprintf(stderr, "filename must end in .ecm\n");
return 1;
}
/*
** Figure out what the output filename should be
*/
if(argc == 3) {
outfilename = argv[2];
} else {
outfilename = malloc(strlen(infilename) - 3);
if(!outfilename) abort();
memcpy(outfilename, infilename, strlen(infilename) - 4);
outfilename[strlen(infilename) - 4] = 0;
}
fprintf(stderr, "Decoding %s to %s.\n", infilename, outfilename);
/*
** Open both files
*/
fin = fopen(infilename, "rb");
if(!fin) {
perror(infilename);
return 1;
}
fout = fopen(outfilename, "wb");
if(!fout) {
perror(outfilename);
fclose(fin);
return 1;
}
/*
** Decode
*/
unecmify(fin, fout);
/*
** Close everything
*/
fclose(fout);
fclose(fin);
return 0;
}

</syntaxhighlight>

@@ Line 14: / Line 14: @@
 </pre>
-The uncompressed image file is now called <code>filename.img.ecm</code> in the same folder as the original.
+The uncompressed image file is now called <code>filename.img</code> in the same folder as the original.
 <b>Source code ([https://beardedmaker.com/gpl-2.0.txt license]):</b>

@@ Line 16: / Line 16: @@
 The uncompressed image file is now called <code>filename.img.ecm</code> in the same folder as the original.
-<b>Source code:</b>
+<b>Source code ([https://beardedmaker.com/gpl-2.0.txt license]):</b>
 <syntaxhighlight lang="c">

Code: unecm - Revision history

Beard at 16:50, 26 July 2019

Beard at 16:46, 26 July 2019

Beard at 19:38, 8 May 2018