Re: Debian TVIO like PVR
nate wrote:
>
> Dave Carrigan said:
> > "Paul McHale" <pmchale@doubleesolutions.com> writes:
> >
> >> I know the Tivo doesn't have much horse power. They are case in
> >> point for a design which is just fast enough. They appeared to
> >> have spared every expense. It is an awesome unit. Just saying, I
> >> don't think they have a 600MHz processor ... Could be completely
> >> wrong.
>
> > As you can see, it is a 54MHz PowerPC chip with 16MB of memory; not
> > a powerhouse by any means.
>
> it is a powerhorse when it comes to video capture though.
> i have a tivo and i also do a ton of video capture from
> it(i haven't hacked it, not going to touch the insides
> of it until tivo goes under and i dont have any other
> choice). i have a 1.3ghz athlon with wintv pci and
> 768MB ram with a dual 20GB raid0 array. tivo
> can easily encode in ~640x480(approx what NTSC is).
> wintv on my athlon struggles to encode at 320x240.
> infact i make it a point NOT to move my mouse cursor
> when capturing otherwise it will drop frames. CPU isn't
> really a factor as the cpu hovers between 15-45%. just the slightest
> movement of the mouse and it drops a frameor 2. its a very fragile setup, i restart X frequently
> and i disable opengl in my nvidia drivers when i want
> to capture, and re enable it when i want to play unreal
> tournament. otherwise it drops more frames. I/O is not
> a limitation either, the video is
> encoded at a compression level that drops the bitrate
> to ~90kbyte/second. so adding a 50-disk raid0 array wont
> do anything.
>
One thing to remember is that the Tivo has a few minor advantages:
1) Your serial port/USB port probably has a fairly high-priority
interrupt, this is why your mouse movement will cause your processor to
stop working on the encoding.
2) The Tivo probably has hardware dedicated to the specific purpose of
video processing (a FPGA/CPLD type device, or maybe even an ASIC), where
as your PC has to make do with a general-purpose microprocessor.
3) Your microprocessor is a CISC device (i386 class, etc are all CISC
processors). I would guess that it is quite likely that the different
execution times for the different instructions would be a challange in a
realtime (or near realtime) environment. The PowerPC is a RISC chip,
which (among many other things...) means that every opcode on the chip
will average about the same (around 1.5 to 1.7 cycles/instruction IIRC).
It may not be a real big deal, but then again, might be interesting to
see how performance is with Debian on PPC.
--Rich
_________________________________________________________
Rich Puhek
ETN Systems Inc.
_________________________________________________________
Reply to: