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Archive for June, 2011

Blackmagic Decklink SDI and Linux

June 24, 2011 6 comments

Almost a year ago, I invested in a central London based post-production company. At the time, I had dreams of pushing open source software solutions into the professional post-production arena. Things haven’t quite worked out as planned, and I’ve made very limited headway on this project. Business imperatives took over and changing a whole ecosystem is a big job. I’ve continued to use Linux on my laptop and happily connect to printers and network drives, but that’s about all.

Recently I had an opportunity to change all that. We needed a tape digitisation solution, separate from our Avid editing suites, for a new project. I’ve know for a while that Blackmagic’s Decklink range of cards work with Linux and were pretty good for capturing from SDI. We purchased the basic Decklink SDI card, re-cycled an old machine onto which I installed Linux Mint Debian and away we went….

Things weren’t entirely smooth from the start. I upgraded the Mint Debian ISO, including the kernel to 2.6.39. This was my first mistake. The card was not recognised with this kernel. Booting into the original 2.6.32 kernel overcame this problem and the card was recognised. I had to download the relevant Linux software from the Blackmagic website, as the accompanying DVD only included Windows software. The available Linux software from Blackmagic included the relevant drivers, firmware and Media Express software. Unfortunately, other advertised items such as the drive speed test and alpha keying utilities are not available for Linux.

Once everything was up and running, it was time to capture. The Media Express 2.3.1 software was pretty straight forward to use. Setting in and out points allowed the software to control the J30 Digibeta deck and content was captured in Uncompressed 10-bit YUV formate. The other limited codec options included Uncompressed 8-bit YUV, RGB and MotionJPEG. This uncompressed file was then transcoded to IMX50 using FFMbc. The whole process seemed to work reasonably well, and I’m just now waiting to send the IMX50 sample off for technical inspection.

Unfortunately, the Media Express software as supplied did not provide options to change the SD captured frame size from 720×576 to anything else. Ideally I was looking for 720×608 so that VITC was also captured. A phone call to Blackmagic revealed that this was possible with the Windows and Mac version of their software, but not on Linux. Their Linux SDK did expose the necessary calls, but the software had not been written to include them. Essentially, if I wanted VITC, I’d need to write a capture utility myself. Somewhat disappointing.

Overall, I’m pleased that we now have an SDI capture solution running on Linux. However, the Blackmagic Decklink card still feels a little half baked and Linux was perhaps only an afterthought for them.

In Austria: bob Breitband and the ZTE MF180

June 11, 2011 2 comments

I travel a great deal in Europe. Specifically Germany and Austria. I also use the Internet excessively. UK mobile data roaming rates are absurdly expensive. T-Mobile UK sends me a friendly text whenever I try to use data roaming informing me that it will cost £1 for 3MB, £5 for 20MB or £10 for 50MB. Crazy, and crazily expensive.

I finally decided to bight the bullet and buy a 3G data dongle in Austria. Originally I had thought to purchase something from 3 (Drei), however it seemed that everything advertised was on a two year contract. That’s not for me. Ultimately I went for a bob breitband package. This includes a ZTE MF180 3G dongle/stick and a SIM card. Buying the package for €50 was the easy bit. The package itself was €50 for the dongle, with 1GB data gratis, and then €9 for 9GB per month, on a 30 day rolling contract. €9 for 9GB isn’t too bad, although if you exceed this limit the cost is €4 per GB, which is bad. The other gotcha is that you need an Austrian bank account to setup a direct debit for the monthly payments. I won’t bore you with the details of how I have access to one of those.

After opening the package, inserting the SIM card and then plugging the dongle into my Mint Debian laptop, nothing happened. That’s right, nothing. The dongle showed a red light and Network Manager didn’t recognise any new modem. Cutting long stories short, I unplugged, plugged in, unplugged, plugged in, fiddled and swore for a good hour with no luck. At the point of the customer support help line answering, magically I obtained a connection. The light on the 3G dongle had turned blue. I had no idea how. All is good for the remainder or the day, except that the connection is slower than anticipated. Using speedtest.net, initially I was seeing a download speed of only 1.6Mbps and an upload of 0.10Mbps. Pretty poor. Later in the evening this increased to 2.6Mbps download and 0.3Mbps upload. Still not great.

This morning, I once again found it impossible to obtain a connection? Why? Why? WHY? I extracted the SIM card from the dongle and inserted it into my Nokia N900 phone. With the marvelous help of bluetooth, I easily obtained a data connection. The connection dropped occasionally, but in general all was good. The problem was not with the SIM.

Now that I had a connection again, I used our Googlian friends to search for “ZTE MF180 Debian” for answers. The answer was easy to find. Apparently, the 3G USB dongle is initially recognised as a CD-ROM drive. Eject the drive and everything works. Network Manager asks for a pin number to unlock the SIM, then one is able to connect. I don’t know why the dongle is recognised as a CD-ROM drive, and I don’t know why ejecting it fixes the problem, but it does. Thanks to Christian Amsuess for the information. If everything doesn’t work as expected after ejecting the CD drive, there is more help on Christian’s page.

The network speed is no better today, but at least I’m back online. I wouldn’t recommend bob breitband, even with the cool name, and I certainly would not recommend ZTE MF180 dongle. I’m sure ejecting the CD drive every time I need a connection will become annoying, but at least it works.

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