[FFmpeg-soc] [Patch] Maxis EA XA decoder - GSoC Task

[Michael Niedermayer]

On Fri, Apr 11, 2008 at 04:19:37PM +0000, compn wrote:
> Michael Niedermayer <michaelni at ...> writes:
> 
> > 
> > On Fri, Apr 11, 2008 at 03:41:48PM +0200, Robert Marston wrote:
> > > >  > > > +                    sample = ((((*(src+channel) >> i) & 0x0F) << 
> 0x1C) >> shift[channel]);
> > > >  > >
> > > >  > >  This looks buggy.
> > > >  >
> > > >  > Where do you think the error would occur?
> > > >
> > > >  on some non x86 hardware
> > > 
> > > What exactly you referring to here? The shift operators? A problem
> > > with the Endianess maybe?
> > 
> > Its related to the shifts.
> 
> 
> i dont mean to be rude, but i believe that Robert may need some more verbose 
> output from you :)

Good C knowledge is a requirement for ffmpeg gsoc.
If one uses a strict interpretation of the C standard then there are multiple
bugs in the line above. Iam not doing that, i just mean one actual issue
which can occur on real hardware.

Heres an example to help a little
*(src+channel)= 234
i= 4
shift[channel]= 20
sample=  -512 (normlly)
sample=  3584 (on ILP64)


> 
> > > >  > >  Still wrong
> > > >  > Corrected?
> > > >  no
> > > Am I right in saying the pts should be incremented by 28 *
> > no
> 
> 
> more verbosity needed here too.

Iam not sure what verbosity over

typedef struct AVPacket {
    int64_t pts;                            ///< presentation time stamp in time_base units

is needed? Also there is the source of other demuxers and the source of
the code using pts.
Robert has an application for H.264 SVC (H.264 is one of the most complex
codecs around) how is he planing to understand the existing code and
integrate SVC support if he cannot figure out how to set the timestamps
for an adpcm codec?

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

While the State exists there can be no freedom; when there is freedom there
will be no State. -- Vladimir Lenin
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-soc/attachments/20080411/66b17edc/attachment.pgp>