[FFmpeg-devel] [PATCH] MLP Encoder

Michael Niedermayer michaelni
Thu Aug 21 22:22:58 CEST 2008


On Thu, Aug 21, 2008 at 04:44:27PM -0300, Ramiro Polla wrote:
> On Thu, Aug 21, 2008 at 10:47 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Thu, Aug 21, 2008 at 01:13:32AM -0300, Ramiro Polla wrote:
> >> >> /** Applies the filter to the current samples, and saves the residual back
> >> >>  *  into the samples buffer. If the filter is too bad and overflows the
> >> >>  *  maximum amount of bits allowed (24), the samples buffer is left as is and
> >> >>  *  the function returns -1.
> >> >>  */
> >> >
> >> > i do not belive overflow is possible
> >> > without checking the code too carefull i suspect you got the wrap around wrong
> >> > somewhere
> >> > remember (a+b) & MASK = c & MASKis the same as a & MASK = (c-b) & MASK
> >>
> >> I got a sample from Justin that overflows at this point. I don't see
> >> how masking could help, since the mask only clears LSBs. And I don't
> >> see how it could wrap around (it shouldn't).
> >
> > hmm, if so mlp is poorly designed, anyway where does the limit of 24 bits come
> > from? In the decoder i see a huff_lsbs that is read as get_bits(5) so it
> > should be able to reach 31 ...
> 
> If the raw samples can be encoded with 24-bit, is it not a good idea
> to drop any filter that takes more then this? (remember the codebooks
> aren't really good and just save a few bytes).

if raw is smaller than using 25 bits then yes otherwise no

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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