[FFmpeg-devel] [PATCH] MLP/TrueHD decoder

[Ian Caulfield]

On 15/10/2007, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Mon, Oct 15, 2007 at 05:11:23PM +0100, Ian Caulfield wrote:
> > On 15/10/2007, Michael Niedermayer <michaelni at gmx.at> wrote:
> > > Hi
> > >
> > > On Mon, Oct 15, 2007 at 12:42:25PM +0100, Ian Caulfield wrote:
> > > >
> > > > Is it possible to use av_crc on fractional bytes?
> > >
> > > is the area over which the crc is calculated not a multiple of 8bits ?
> >
> > Not in this case - this header is usually 125 or 149 bits long, and
> > doesn't start on a byte boundary.
>
> just "filling" the first bits which arent part of the header with 0 should
> work as long as the end is on a byte boundary

I don't think the end is on a byte boundary either...

> > What do you suggest I call the not-CRC that MLP uses (the difference
> > being that the order of the table lookup and XOR are swapped)?
>
> MLP-checksum maybe
> also its all fine to call it crc as long as it is one, that is
> before that funky xor
> also my complaint was only about that comment claiming that the used checksum
> would be a a crc just different from what libavutil implements

I'm not so hot at Galois arithmetic and stuff - I assumed it was just
a CRC variant.
I'll work on the comments.

Ian