Lossless HRV data

David J Taylor

#730

For 24 hours from 1300 today, EUMETSAT are transmitting HRV with 
lossless Wavelet compression.

My initial impressions are:

- even with JPEG (quality 82) there was a noticeable improvement on 
images which were histogram equalised to make full use of the 
dynamic range.

- I needed to use PNG save format rather than JPEG to see the full 
extent of the differences

- there is a definite improvement - detail is now visible that could 
not be seen before and the blockiness is completely gone.

- it also shows that if you use Save visible as JPEG in the MSG Data 
Manager then you maybe need a higher quality setting than the 
default value of 82.  

- The greater bandwidth consumed is obvious on the graphs!  The 30-
minute average has gone from something over 108KB/s to around 
138KB/s.

  http://www.david-taylor.myby.co.uk/mrtg/hermes_dvb.html

Cheers,
David

Douglas Deans <douglas@...>

#731

Show quoted text

----- Original Message ----- 
From: "David Taylor" <david-taylor@...>
To: <MSG-1@...>
Sent: Wednesday, October 29, 2003 2:36 PM
Subject: [MSG-1] Lossless HRV data

For 24 hours from 1300 today, EUMETSAT are transmitting HRV with
lossless Wavelet compression.

My initial impressions are:

- even with JPEG (quality 82) there was a noticeable improvement on
images which were histogram equalised to make full use of the
dynamic range.

- I needed to use PNG save format rather than JPEG to see the full
extent of the differences

- there is a definite improvement - detail is now visible that could
not be seen before and the blockiness is completely gone.

- it also shows that if you use Save visible as JPEG in the MSG Data
Manager then you maybe need a higher quality setting than the
default value of 82.

- The greater bandwidth consumed is obvious on the graphs!  The 30-
minute average has gone from something over 108KB/s to around
138KB/s.

  http://www.david-taylor.myby.co.uk/mrtg/hermes_dvb.html

Cheers,
David
Out of curiosity I turned the JPEG quality up to 100.  Added nearly 12Mb on
to the save file size.   Didn't realise it would be that dramatic.  I
suppose 100% on JPEG should be about the same as PNG... it more or less is
from a file size point of view.

Regards
Douglas.

Robert Moore

#732

David, by the time I had a look at this most of the illumination had gone from
Europe, so I went south. With HRV set at 100, saved as JPEG, the images were
incredible. The port of Luanda and the Cape Town hinterland showed marvellous
detail.
Await tomorrow's images of Europe with interest though I doubt we'll get this
degree of detail ... but let's see.

Robert



Quoting David Taylor <david-taylor@...>:

For 24 hours from 1300 today, EUMETSAT are transmitting HRV with 
lossless Wavelet compression.

My initial impressions are:

- even with JPEG (quality 82) there was a noticeable improvement on 
images which were histogram equalised to make full use of the 
dynamic range.

- I needed to use PNG save format rather than JPEG to see the full 
extent of the differences

- there is a definite improvement - detail is now visible that could 
not be seen before and the blockiness is completely gone.

- it also shows that if you use Save visible as JPEG in the MSG Data 
Manager then you maybe need a higher quality setting than the 
default value of 82.  

- The greater bandwidth consumed is obvious on the graphs!  The 30-
minute average has gone from something over 108KB/s to around 
138KB/s.

  http://www.david-taylor.myby.co.uk/mrtg/hermes_dvb.html

Cheers,
David



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Professor Robert Moore
Department of Sociology, Social Policy
   and Social Work Studies
The University of Liverpool
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