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#include <stdio.h>
#include <string.h>
#include <mad.h>
#define ALL_FRAMES 16384
int decodemp3(const unsigned char * key, const char * block, int skipframes, int maxframes,
char * decoded, int * len)
{
struct mad_stream stream;
struct mad_header header;
int framecount = block[4]*256+block[5];
char xorred_frame[16304+MAD_BUFFER_GUARD];
int i;
int result = 0;
for(i = 0;i < 16304;i++)
xorred_frame[i] = block[i+32] ^ key[i&3];
memset(xorred_frame+16304,0,MAD_BUFFER_GUARD);
mad_stream_init(&stream);
mad_header_init(&header);
mad_stream_buffer(&stream, xorred_frame, 16304+MAD_BUFFER_GUARD);
if(framecount > maxframes)
framecount = maxframes;
*len = 0;
for(i = 0; i < framecount; i++)
{
if(mad_header_decode(&header, &stream) < 0
&& (stream.error != MAD_ERROR_LOSTSYNC ||
i != framecount-1))
{
printf("%d\n",stream.error);
result = -1;
break;
}
if(skipframes)
skipframes--;
else
{
memcpy(decoded + *len,stream.this_frame,stream.next_frame - stream.this_frame);
*len += stream.next_frame - stream.this_frame;
result++;
}
}
mad_header_finish(&header);
mad_stream_finish(&stream);
return result;
}
int main(void)
{
FILE * f = fopen("/media/disk/HMDHIFI/ATDATA02.HMA","rb");
const unsigned char key[] = {0x00,0x69,0xF7,0x7A};
// 00641418
int firstblock = 0x60;
int firstframe = 0x0;
int lastblock = 0x12d;
int lastframe = 0x1e;
int b;
int len;
char block[16384];
char decoded[16384];
fseek(f,firstblock*16384L,SEEK_SET);
for(b = firstblock;b <= lastblock;++b)
{
fread(block,1,16384,f);
if(decodemp3(key,block,(b == firstblock) ? firstframe : 0,
(b == lastblock) ? lastframe : ALL_FRAMES,
decoded, &len) < 0)
{
fprintf(stderr,"decoder failed at block %d\n",b);
return 1;
}
fwrite(decoded,1,len,stdout);
}
return 0;
}
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