[oclug] PVR-Personal Video Recorder using Linux

[Brad Barnett]

On Wed, 14 Jan 2004 21:09:52 -0500
Christian Mautner <oclug at mautner.ca> wrote:

> On Wed, Jan 14, 2004 at 04:35:36PM -0500, Brad Barnett wrote:
> > On Wed, 14 Jan 2004 15:59:37 -0500
> > Philippe Piche <ppiche at cisco.com> wrote:
> > 
> > > Anyone doing this as a hobby project?
> > 
> > Check out MythTV.  It isn't a TiVO, but it supports live-tv pause,
> > rew, ff, etc.  It also has quite a few nice add on modules.
> > 
> > Eventually, it will surpass TiVO.  Build your own box, but I'd
> > probably populate it with some dedicated video input cards.  The more
> > you have, the more streams you can record at once ;)
> 
> Perhaps. But on a K6-2 500MHz? Forget it right now. The way MythTV
> works is that it constantly encodes the stream, and to watch it you
> decode it online. This allows for time shifting, but it requires a
> fairly fast system. I tried it on my Athlon XP 1700+ and it was too
> slow. You might want to try one of the supported hardware mpeg
> encoding cards (don't know which ones are supported though).

This certainly was not CPU.  MY P4 2.4GHZ box uses a _less_ than 10%
cpu when doing the above task, and that was doing a full 720x480 encode. 
Most of the time tools like top and gkrellm show 5% usage.  A P4 is
actually much slower (per clock rate) than a P3, so CPU wasn't your
problem.

Throughput most likely was.  Did you have DMA turned on, as well as
several other hdparm settings?  Did you monkey with elvtune and what not
as well?  How about turning off atime?  Older motherboards / ide
controllers / etc are often much more CPU intensive with hard drive write
and reads than newer, as well.

Definitely not a cpu issue, anyhow.  Monkey a bit with the above settings,
and you'll be good to go.  Of course, for any _true_ TiVO functionality,
you'll need to definitely go with something that does what MythTV does.

Otherwise, you won't be pausing that live tv, or watching two channels in
software pip (or more).

> 
> I am currently trying to set up my system with freevo which apparently
> allows to watch TV directly and on-line, which should work. Recording
> should be possible, but it's considered work in progress, so I don't
> have too big hopes there.

Freevo is great, but fairly young.  Recording isn't an issue though, it
works fine here.  After all, it just uses mplayer (although they've moved
away from that in later releases) to do so.

My low-tech recording scheme with mplayer is a script, ala:

#!/bin/sh

if [ "$1" = "" ] ; then
 echo "Use VCR <recording time in minutes> <filename>";echo "Please give a
time!";exit fi

if [ "$2" = "" ] ; then
 echo "Use VCR <recording time in minutes> <filename>";echo "Please give a
filename!";exit fi
sudo /usr/bin/aumix -lR -i70
/usr/bin/mencoder -tv driver=v4l:width=320:height=240:input=1:norm=ntsc -o
$2 -ovc lavc -lavcopts vcodec=mpeg4:vhq -oac mp3lame -lameopts cbr:br=128
-endpos $1:00 tv:// > /dev/null

Works like a charm. ;)  I simply run the script using "at", and I have
whatever recording time I want.  I also have a higher definition script,
for 640x480 capture with 192 kbps audio.

> 
> Furthermore, you say you want to use your "ATI AIW Radeon 32MB", the
> AIW meaning all-in-wonder I assume, for which there are no Linux
> drivers, as far as I know. (The TV tuner stuff that is, the video card
> works fine.)

There is the GATOs project, but I wasn't very impressed with it when I
looked a year ago.  I don't know if that's changed much in the last year.


> 
> chm.
>