Re: [Debconf-video] Advice about a video system
On 02/16/2011 12:22 AM, Wouter Verhelst wrote:
> On Tue, Feb 15, 2011 at 11:31:40AM -0600, Carl Karsten wrote:
>> PC to run DVswitch: $600 ish. It does not need lots of CPU or ram.
>
> Actually, I disagree with that one. You do want a somewhat modern PC for
> the machine that will do the switching. The RAM doesn't need to be
> extreme, but since you'll be decoding several streams, scaling them,
> possibly combining several of them in a pic-in-pic or fade effect, and
> finally re-encoding the stream, it does need quite some CPU power.
>
> On my laptop, which has a 2Ghz Core2 duo, I've experimentally discovered
> that you can do about 7 streams if you want fade, or up to nine if you
> don't, without performance issues. Granted, most setups won't need as
> much, but if you're doing dvsource-alsa, twinpact, two cameras, and a
> sponsor stream, you've already got five streams to decode.
A word of warning (based on previous experiences): it is critical that
the graphics system is somewhat sane, and can handle Xv (can't remember
if that's the video extension DVSwitch uses) without requiring a huge
amount of CPU overhead.
I remember ending up in a situation with an unusable recording when
Picture-in-Picture was used - it turned out the display on this
particular machine was using the "vesa" driver or something similarly
poor performancewise, and this was causing one of the two cores to load
up just displaying video - which combined with the added overhead of PiP
caused frames to be dropped.
Pretty much any video card can be made to handle video properly under
Linux, but do be sure to run a test like this beforehand to avoid any
embarassing situations!
Dave.
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