wwp@yahoogroups.com:
Re: Full Screen VR
Hans Nyberg 2004-Jun-29 19:08:00
on 29/06/04 20:03, Andrew #removed# wrote:
> Note that Panocube uses an irregular scale which is not standard.
> A compression of 50% in Panocube is equivalent to a compression of 32% on
> the IJG ( Independent Jpeg Group ) scale which is used by QuickTime tools
> and in Photoshop on Mac and PC.
> A Panocube compression of 78 is equivalent to 50 on the scale used by other
> software.
:-))
> Just want to clarify that PanoCube's (PanoTool's) scale is "irregular" for
> Hans only. As I wrote earlier in to this group PanoCube has standard JPEG
> scale from 0..100. By "other software" Hans perhaps means CubicConverter which
> really uses non-linear scale 50% from CubicConverter corresponds to 78% of
> JPEG standard, 75 from CubicConverter corresponds to 92% of JPEG standard.
> This was tested with jpegdump and everybody could check it by own.
So you mean that the scale which is used by Adobe and Quicktime and which
corresponds very close to the independent JPEG Group is not the standard.
This is a good article where you can also see how the IJG compression and
the photoshop are very close to each others.
http://www.photo.net/learn/jpeg/#ijg
According to the above article JPEG dump measures the IJG compression
scale.
I do not know how you measured it with Jpegdump. but it definetly does not
correspond to
IJG or Photoshop. compression rates.
The fact is that a movie compressed with CubicConverter or any other tool
at 50% has a compression rate of approximately 1-20
The same image used in Panocube gives a compression rate of 1-30.
Photoshop compression of the image also gives you close to 1-20 even if you
can not compare that exactly with a QTVR. Remember that the source has to
be the
sizes of the Cubefaces, not the equirectangular image. They do not match in
Panocube.
or in the default settings from CubicConverter.
The problem is that it is not possible for Panocube users and users of other
tools to talk together about it. If I recommend people to use a compression
of 50% it should give them the same quality whatever software they use.
Hans
Hans Nyberg
commercial photographer
hans nyberg fotografi
hasselvej 6 DK-8550 ryomgaard denmark
<http://www.hans-nyberg.dk>
<http://www.qtvr.dk>
<http://www.virtualdenmark.dk>Denmark in QTVR Panoramas
<http://www.panoramas.dk> Panoramas.dk - Features Fullscreen QTVR
email: #removed#
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