frankk2ncc escribió: > I don't understand nearly what it would take to do this, but what a clever > thought! Would it work on something already compressed, like a JPEG via SSTV > without further loss? > > > f, k2ncc > > > > --- In digitalradio@yahoogroups.com, "Simon \(HB9DRV\)" <simon.br...@...> > wrote: > >> Thinking to myself - when we use a mode such as Olivia / MT63 with extensive >> error correction, why don't we compress the text? >>
Actually, like PNG, which is zipped (lossless) BMP. But compressed material already has little redundancy, so actually you may LOSE compressing already compressed files by any means, as you start adding headers and other stuff to the resultant fles.. But analog SSTV is meant to transfer images, not files. It would certainly be adventageous for file transfer modes. It is quite important to acknowledge the fact that you must already know what you really NEED. If you don't need to send formatted material, .txt is enough, so why use .doc? If you are sending a schematic, black and white, 16 color PNG may be pretty adequate, instead of 24 bit color, and so on. Use the least voluminous option whenever possible. Also, beware of compression, particularly lossy compression, like JPG, when sending line diagrams, because the lost detail creates artifacts around the lines. Once I received a 24 bit color schematic via packet, which black lines over a white background, 200 kB took one hour to transfer. I made the corrections , converted to B/W, reduced to 4 levels per pixel (avoiding artifacts, I have used Irfanview for a quite long time), saved it to PNG and it took only 3.2 kB. The transfer time of my answer was 4 minutes.on a shared packet channel. 73, Jose, CO2JA __________ Información de ESET NOD32 Antivirus, versión de la base de firmas de virus 3832 (20090206) __________ ESET NOD32 Antivirus ha comprobado este mensaje. http://www.eset.com Participe en Universidad 2010, del 8 al 12 de febrero de 2010 La Habana, Cuba http://www.universidad2010.cu --------------------------------------------------------------------- SEGUNDO SEMINARIO INTERNACIONAL LEGADO Y DIVERSIDAD. ARQUITECTURA Y URBANISMO. El rescate de los valores urbanos y arquitectónicos en tiempos de globalización Colegio de San Gerónimo, La Habana Vieja, noviembre 24-27, 2009 ---------------------------------------------------------------------
