[linux-dvb] Fastest way to display a bitmap on DVB-s

[Ralph Metzler <rjkm@convergence.de>]

Roland Praml writes:
 > does anybody know what's the best way to display a bitmap (with low CPU
 > usage)?
 > I have written a small programm with that I can decompress
 > divX movies (I already can write an uncompressed "bitmap stream" to HDD)
 > So my idea is to send the stream to the DVB-s card.
 > Is it possible to send a bitmap to DVB driver so that it is displayed
 > fullscreen. (I need to do that 25 times per second). Or should I go an

Definitely not.
Fullscreen display in YUV format would be possible if no decoding is
on (otherwise there is not enough memory for OSD) but the data rate of 
(720x576 pixels/frame)x(2 bytes/pixel)x(25 frames/s) > 20Mbytes/s
is already too high for the mode the DEBI port has to be used in.
(I tried faster modes, they don't work).
This is not even counting the substantial communication overhead 
caused by the small DPRAM size (4KB) (many, many IRQs ...) 
and the copying on the other side from DPRAM to SDRAM which would have
to be done by the 40MHz ARM.


 > other way and reencode the stream as MPEG ? (can the card handle a stream
 > that only contains I-frames, I think this will make some things easier?)

This should be possible if the data rate stays low enough (AFAIR <15 Mbit/s).



Ralph


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