David Glover

Note: This was previously posted in an earlier version of my blog, but I’m reposting it here because of the surprising popularity of that article.

Yesterday from a dusty shelf I discovered my Sony DV camera. And after playing with it for a while I discovered (or possibly re-discovered, as I might have just forgotten) that it has analogue video inputs that it will digitise and then spit out of the DV port.

So this gave me an idea - this is essentially what the Slingbox does, except the Slingbox outputs a network stream rather than DV video. But I have a Mac Mini sitting underneath my TV downstairs, and that has a DV port on it…

So, after a lot of bodging and hacking and plugging of cables… I have this:

Patricia Hewitt in a window! Or, more accurately, the output of my Sky box being converted to DV, fed into my Mac Mini, transcoded, and then multicasted (yeah baby) across my house LAN.

And here’s how I did it.

My camera came with a video cable ostensibly for spitting out video to your TV - but it works backwards too, so I connect it to the back of my Sky box.

(Dusty, yuck.)

The other end connects to my camera, and another cable feeds DV out from my camera and into the back of my Mac Mini.

On the Mac Mini I download and install QuickTime Broadcaster, which is free. Setting it up, I start with the “LAN” presets for both Video and Audio, then hit “Show details” and do a few modifications. The Audio settings work unchanged except for choosing “DV Audio - first two channels” for the Source. Video settings look like this:

Things I changed are:

Size: 512×288.
288 is half the vertical lines of PAL. If I wanted full resolution I would have chosen 576 lines but the CPU in my Mac Mini isn’t capable of encoding that at 25fps. Halving the vertical resolution also has a handy side-effect of deinterlacing the video. 512 pixels wide results in a 16:9 display, for non-widescreen programs I would choose 384, but 99% of all UK TV is widescreen, so I’ll never need to change this. NTSC users might choose 427×240 or 320×240.

Quality: High
Frames per second: 25 (30 if my source was NTSC.)
Key frame every: 50 (60 if my source was NTSC.)
Limit data rate: Off (No point on a LAN.)

Network settings:

Things I changed are:

Transmission: Multicast

Then just hit “Generate IP Address” and you’re done.

Save the settings as an SDP file and then hit “Broadcast”. From another Mac (or PC), load up the SDP file and voila! DIY Slingbox.

Advantages over a Slingbox:
* No extra hardware to buy. (If you already own a DV camera and Mac server of course. You could also use a dedicated DV bridge if you have one.)
* More than one person can watch.
* Better video and audio quality.

Disadvantages over a Slingbox:
* No remote control functionality. (Which I’m doing by using an TV Link and existing RF cabling. Not ideal.)
* Harder to setup.
* Doesn’t work over the internet. (Though it could do, if have access to QuickTime Streaming Server.)