PanoTools NG:
Re: New hardware testing on PTgui performance
Helmut Dersch 2007-Dec-30 13:11:40
Hi Matt (and others),
thanks a lot for the interesting speeddata! I was about to
ask for benchmark data of current stitching software/hardware
for my current project of a fast stitcher.
As has been mentioned in this thread, IO related bottlenecks
are due to the use of uncompressed fileformats, if not for
the final then for intermediate tempfiles. A request to
the authors of frontends to my pano-libraries (ptgui, nona,...):
please insert the line
TIFFSetField(tif, TIFFTAG_COMPRESSION, COMPRESSION_PACKBITS );
when writing tempfiles and you will save those poor users the need
to buy terabyte-drives, and execution will be much faster.
My own stitcher frontend PTStitcher used this format since the
first release. Even gigapixel panoramas with > 1000 source images
should never require more than 100 GByte scratch.
As to RAM-requirements and speed:
All pano12-based stitchers scale poorly with target panorama size.
This is due to the original design as plug-in for graphics programs
(first for GraphicConverter on Macs, then Photoshop and Gimp).
One source and one full sized copy of the target panorama must fit
into memory, which is no problem for a plugin, since the host program
provides this storage. Also, a fullscaled panorama image is created
for each input image.
However, there is no need for all this in a standalone stitcher.
No random access to either source nor target image is required,
and only a small fraction of the target panorama actually needs to
be rendered for each image. Therefor, image processing can
be done in a streaming fashion, with minimal RAM requirements.
At most one source image should fit into memory, and even that
can be relaxed without significant penalty. I am currently
looking into this and will post some results for a reworked
fast pano-library hopefully soon.
Regards
Helmut Dersch
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