[mythtv-users] So, how does the SlingBox Pro HD do it?
brad+myth at templetons.com
Mon Jan 15 19:29:37 UTC 2007
On Sun, Jan 14, 2007 at 08:13:26PM -0800, Marco Nelissen wrote:
> >http://us.slingmedia.com/page/hdconnect.html says:
> >"The HD Connect Cable lets you watch your home televisions high
> >definition programming by connecting your HDTV source to the Slingbox
> >PRO. The HD Connect Cable has component video and stereo audio inputs
> >and pass-through outputs, and is compatible with HDTV video services of
> >up to 1080i resolution."
> >The Slingbox Pro is $199; the HD Connect cable is another $50. So,
> >internally the Slingbox is taking a 1080i component input and converting
> >it into something that can be broadcast over the Internet. In this
> >message board we've discussed how it costs kilobux to take uncompressed
> >HDTV and convert it into MPEG-2; even if Sling isn't converting to
> >MPEG-2, they're still doing _something_ at < $250.
> >Anyone know the internals of what's going on?
> I'm just speculating here, but since it captures component, which is
> analog, it's fairly easy to reduce the size on the fly by capturing
> at a lower horizontal resolution. Capturing 1920x1080i at 320x1080i
> would give you 1/6th the original image size for example, and therefore
> 1/6th the raw datarate. You could probably reduce it even further by
> dropping every other scanline, but even 320x1080i gives you a low
> enough datarate that it could be processed either in software or by
> fairly low-cost custom hardware.
Almost surely, and indeed, you don't want to capture all the scan lines
since that just leads to annoying deinterlacing anyway, though you
might capture all 540 of the lines in a half-frame, and then just
discard the 2nd half-frame. For 720p you could skip every other line
to get 360 lines, which is I think still more than the slingbox usually
The slingbox sends the video back out your slow upstream connection,
usually something on the order of 384kb for the typical customer so
it's way less than SDTV by the time it's done.
In theory, we myth users should never want a slingbox. If we want
to remotely view we could set up for automatic transcode of our programs
followed by easy streaming of the results. There are some ways to
do this, like mythstreamtv and vlc, but I've never been satisfied
with them. Oddly, the slingbox real time streaming does a better
looking job, when you would think non-real-time transcode, given even
a modest head-start, should be able to do much better even without
custom hardware. And you lose all of Myth's nice features you've
come to love -- automatic commercial skip, even of live shows,
time compress etc.
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