Wednesday, September 10, 2014

Ongoing Barnfind notes

As I get more familiar with Barnfind's products I need to make a note of some of their gotchas!

  1. The Tx and Rx lights on all SFP ports are not data lights, rather they are clock lights and as such only light when you're dealing with synchronous broadcast signals - HD/SDi, MADI, AES etc.
  2. The CWDM multiplexer/de-multiplexer (they are exactly the same unit!) works both ways and if you have signals going bi-directionally on a fibre each port is an input or an output; that takes a bit of getting your head around!
  3. In a similar vein the wavelength quoted on SFPs (1350nM in this image) only really applies to the transmitted signal; SFPs are "colourblind" - they don't mind what wavelength they receive. So, once a signal leaves the CDWM de/multiplexer you can take it into any of your SFPs for input to the crosspoint router - again, it's not particularly intuitive as we're used to "tuning" or "demultiplexing" other signals to the frequency they'll be used at.
  4. The BarnStudio software; the manual says that it comes set up hard-set to a address; our didn't, it was setup for DHCP and since it doesn't respond to multicast PINGs it took me a while to figure this out.
  5. If you are routing ethernet out to the multiplexer it is always directional (i.e. it takes up the in and out of an SFP and needs two ports on the multiplexer). 
  6. See note 1 above (no activity lights) for ethernet.
  7. If you're using the same machine to drive BarnStudio and test an ethernet connection (by sending it via an ethernet SFP -> fibre -> multiplexer -> BarnMini -> SFP -> ethernet) you run the risk of an ethernet loop and subsequent broadcast-storm! Wesley & I suffered this and couldn't figure out why the entire workshop network was down. Much better to use your rucksack router & a RaspberryPi as a separate test network.
  8. The BarnStudio software - although good, is a tad hard to read initially as if you give the ins and outs proper names they re-order alphabetically rather than in order of the SFPs and BNCs. Just remember - inputs are down the left axis and outputs are along the top (most things are present in both).

Tuesday, September 09, 2014

HD playback - how we did it a quarter of a century ago

In 1988 I went to a demo of HDVS in Studio 2 at Television Centre; the left-hand image shows the 1" uncompressed RGB recorders that ran around eight times the speed of regular C-Format videotape. On the right is current-model Blackmagic Hyperdeck Shuttle - a small HD/SD record/playback box that uses SSDs and can handle uncompressed, ProRes and Avid DNxHD. It's in pieces 'cause I'd just finished fixing it and was testing it. BUT, given that they are two-hundred quid you might wonder if they're worth fixing?! The Sony was definitely worth fixing as each machine came in at >£100K.

Makes me wonder what I'll be doing by the end of my career?!