Re: Lossless HRV data

Douglas Deans <douglas@...>

----- 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


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.


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