Hi On Wed, Feb 15, 2006 at 11:19:41PM +0100, Alexander Strasser wrote:
Hi,
the checksum definition in the current spec seems incomplete or unprecise to me. I have prepared the following patch to complement Oded's last change. It is based on the last discussion of the subject on mplayer-dev-eng.
It is just a suggestion.
hmm, alternative suggestion: crc32 checksum The checksum is choosen so that c(x) is a multiple of x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1 over GF(2) c(x) is the polynom coresponding to the block from and including the forward ptr and upto and including the checksum c(x)= (1&(d[0]>>8))*x^(n-1) + (1&(d[0]>>7))*x^(n- 2) + ... + (1&(d[1]>>8))*x^(n-9) + (1&(d[1]>>7))*x^(n-10) + ... + ... + ... + (1&(d[n/8-1]>>1))*x^1 + (1&(d[n/8-1]>>0))*x^0 alternatively you can simply run crc=0; for(i=0; i<size; i++){ crc ^= buf[i]<<24; for(j=0; j<8; j++) crc= (crc<<1) ^ (0x04C11DB7 & (crc>>31)); } over the data btw, why doesnt the syncpoint have a packet header / forward ptr !? [...] -- Michael