I am working on encoding Dirac using Schro encoder in VLC. It should be
ready for testing in a week or two. I'll post a patch to the Schro
developers list. Currently, the dirac-research implementation is used in VLC
for coding Dirac and it is very slow. So using Schro should speed up the
encoding.
Regards,
Anu
On Tue, Nov 2, 2010 at 12:36 AM, salsaman <salsa...@gmail.com> wrote:
> On Mon, Nov 1, 2010 at 7:30 AM, Tim Borer <tim.bo...@bbc.co.uk> wrote:
> > Hi,
> >
> > I would be interested to hear the results of experiments comparing Dirac
> Pro
> > and J2K. I assume you will be comparing Intra Dirac, i.e. Dirac Pro/SMPTE
> > VC-2, with J2K?
> >
> > As you say Dirac Pro's entropy modelling is quite different to J2K. I
> doubt
> > it yields a higher compression ratio - the objective with Dirac Pro was
> to
> > produce a simpler, less complex solution rather than a higher compression
> > ratio. However I would add that, because Dirac Pro takes care to preserve
> > the DC precision it can have fewer visual artefacts than J2k (even if
> PSNR
> > figures don't show this). I say this because we have noticed that J2K,
> used
> > for video, can produce an annoying DC flicker even at quite low
> compression
> > ratios.
> >
> > I did some (unpublished) experiments a few years ago comparing J2K and
> Dirac
> > Pro. With arithmetic coding enabled the compression efficiency (for
> lossless
> > coding) was almost identical for the two codecs (some images were 1 or 2%
> > better with one codec and the other way round for other images).
> > Interestingly when arithmetic coding was disabled, so that entropy coding
> > was only the fixed variable length coding (interleaved exp-Golomb), the
> > compression efficiency of Dirac Pro only dropped by 20%. That is for
> > lossless coding arithmetic coding only appeared to give a compression
> gain
> > of 1.25. Given that arithmetic coding adds significantly to the
> complexity
> > of the codec some applications may prefer the option of not using
> arithmetic
> > coding in Dirac Pro for lower complexity at the expense of slightly
> reduced
> > compression.
> >
> > At the moment there are low delay profile hardware implementations of
> Dirac
> > Pro/SMPTE VC-2 available from Numedia Technology and from Westwood Rock.
> > Software implementations are available in the Open Source Schroedinger
> > software and from Entropy Wave.
> >
> > Regards
> >
> > Tim
> >
> > Dr Tim Borer
> > Lead Engineer
> > BBC Research & Development
> > BBC Centre House
> > 56 Wood Lane
> > London W12 7SB
> >
>
> Hi Tim,
> Glad to hear somebody is actively working with dirac. I got the
> impression when I was rewriting the ogg/dirac demuxers for LiVES and
> VLC that nobody was really using the dirac format any more.
>
> Regards,
> Salsaman.
>
>
>
> http://lives.sourceforge.net
> https://www.ohloh.net/accounts/salsaman
>
>
>
> http://lives.sourceforge.net
> https://www.ohloh.net/accounts/salsaman
>
> > At 20:46 30/10/2010, javasharp...@ukr.net wrote:
> >
> > Hi,
> >
> > I want to do some experiments with dirac and j2k and I have a question.
> As I
> > see dirac's entropy modelling is totally different from that of j2k. It
> > would be interesting to know the rationale behind it. In particular if
> the
> > j2k's entropy modelling (together with the dirac's arithmetic encoder
> which
> > as I understans is more effective than j2k's quasi-arithmetic encoder)
> what
> > size decrease can be expected?
> >
> > Thanks in advance,
> > Vladimir
> >
> >
> >
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