Re: Did Huygens send JPEGS?

From: Thomas Womack (twomack_at_chiark.greenend.org.uk)
Date: 01/22/05 

To: sci-space-tech@moderators.isc.org
Date: 22 Jan 2005 12:00:43 +0000 (GMT)

In article <IAoxG4.8K1@spsystems.net>,
Henry Spencer <henry@spsystems.net> wrote:
>In article <41F112EB.587C0D01@eagle.ca>,
>G. R. L. Cowan <gcowan@eagle.ca> wrote:
>>The files now at http://esamultimedia.esa.int/docs/titanraw/index.htm
>>are 176-by-768 JPGs. Where the same terrain is in five or 10 frames,
>>it seems conceivable unprocessed bitmaps could somehow be combined
>>to yield a little more resolution, but I guess JPEG compression would
>>eliminate that possibility.
>
>Nobody sends unprocessed bitmaps, or even losslessly-compressed bitmaps,
>from planetary probes any more. Images are invariably compressed using
>JPEG, or variations thereon, before transmission.

The impression I get from the Cassini raw-images site at NASA is that
the images are losslessly compressed, except that if the compression
produces more than 1024 output values from two 1024-pixel lines, the
last ones are cut off. That produces a "comb" effect down the side of
the image which can easily be sorted out by interpolation, without
producing JPEG's block artefacts with their catastrophic effect on
many forms of image sharpening.

Tom

Relevant Pages

  • Re: Did Huygens send JPEGS?
    ... Nobody sends unprocessed bitmaps, or even losslessly-compressed bitmaps, ... Images are invariably compressed using ... The scientists would prefer not to have to deal with compression artifacts ...
    (sci.space.tech)
  • Re: Did Huygens send JPEGS?
    ... The MER rovers routinely send losslessly compressed images. ... accidentally sent a few unprocessed bitmaps that were not compressed at ... because the wrong option was used on the command (lossless ... compression was what was intended). ...
    (sci.space.tech)
  • Re: need help with distiller error
    ... compression) that intentionally discards pixels in an image. ... observed from the use of JPEG Compression. ... fact that JPG compression cumulatively degrades images. ... One, maybe even two or three passes through JPG compression, fine. ...
    (comp.publish.prepress)
  • Re: Differential intra-interchannel filters for RGB images lossless compression
    ... >>> However IMHO many photographic images are even slightly more difficult ... don't look right, lighting doesn't look right, surfaces are almost always ... compression, it seems concievable to me that they could. ... would likely be able to fairly accurately predict the pixel. ...
    (comp.compression)
  • Re: Image size publisher 2003
    ... Then go to one or more of the images, ... Publisher file, and producing it with a second Publisher file, and ... When I pre view as a webpage it works great, but when I upload to server ...
    (microsoft.public.publisher.webdesign)