[mythtv] 3 Channels Simultaneously, just expand with a DSP

mbox at cloppy.net mbox at cloppy.net
Wed Feb 5 16:50:40 EST 2003

I expect to, other do, why would one do that?

Isn't it common to watch a channel whilst recording another one? Then we should 
be able to run record+liveTV, those are 2 channels.
Whilst ads pop out, one may want to zap and delay liveTV. There would be the 
need for 3rd channel abord?
3 data streams may then be the minimal. We may even expect a 4th stream if we 
consider managing data in the background (e.g. mp3, DivX or SVCD generation) or 
video editing (camera stream, ads cut-out, ...).
So some people may enjoy to handle up to 3-4 data streams on a single box (or 
shared on back/front end).

For the time being I forgot dual CPU box (too loud, too hot) and will not start 
with back/front ends (too expensive assuming this back end should be a fast 
dual CPU). Did anyone think about pluging in some dedicated MPEG DSPs in a free 
PCI slot?

Take a look at the linux parallele processing FAQ, chapter 5.2, "Did You DSP 

Take a look at commercial PVRs, commercial set top boxes, chips and 
architectures designed for such intesive video applications: they are all build 
around grabber/DSP/PCI chipets. We have grabbers and PCI slots, we need DSPs :-)

This is an example of what is required to speed up real time MPEG 
compression/conversion, a huge 4 GFLOPS/6400 MIPS CPU expansion:

That one may cost several $10.000... We just have to find out who designed the 
affordable and documented PC compatible DSP board?
The CPU will then just have to handle data exchanges accros PCI bus, boards, 
drives and network. Further advantage would be DSP code, codecs being 
accessible to GNU community and MythTV quality not being dependant of hardware 
and hardcoded bundled TV/DSP boards.

Could anyone dig out such a DSP board, inexpensive (the chip itself, RISC or 
FPGA, costs around $25 for q25.000), with linux drivers for realtime video 
streams processing? Is any one close to and may contact Analog, Cyrix, Texas or 

Please, put that DSP on the wish list, your PII 800MHz will enjoy such 
You will think I'm dreaming but I often noticed what I dreamed about is 
downloadable somewhere from internet :-)


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