It’s possible to run R just from a prompt, which works well for individual commands but isn’t great for editing those commands or keeping track of what you did. Looking around, I found that there is (of course!) a Vim-R plugin available, so I gave it a try – and really liked it! It is enabled for files ending in .R or .Rmd and allows you to launch an R prompt and run one or many lines in that prompt directly from vim.
The .Rmd format is actually for R Markdown, which is a markdown format that lets you embed R. I’ve been using it as a sort of lab book to keep track of what I did and why. You can then generate a document with all the R code shown and evaluated – very neat!
Donna’s been a virtual friend for a few years; I “intermet” her when I was preparing to host the Dutch PHP Conference in Amsterdam, in 2010. I had some great role models from the PHP community to show me how to “ringmaster” at a big conference, but I was unsure how it would look on a woman. Having already done a similar role for PHPNW, I’d had negative feedback about being teacherish (something that I still get complaints about), and I wasn’t sure how else to wear that role. Lots of things work well for men but not for women (silly things, swearing on stage (this differs between cultures), asking for a pay rise, falling out of bed into whatever free conference shirt you were given yesterday ….) and I was determined not to turn myself into a decorative but ditsy hostess.
My good friend Kathy Reid talked through my anxieties with me, and sent me a link to a video of Donna introducing an even more major conference: Donna organised Linux Conf AU and the video showed her introducing it with equal helpings of excellence, approachability, and entertainment. Confident that I wasn’t alone, I stopped worrying and gave that conference my best shot. Continue reading
$response = $app->response(); $response->header("Content-Type", "text/javascript");
The $app variable is the Slim\Slim instance for your application, once you have that, you can just add on any headers you need to with this call to header(). It wasn’t obvious to me and there weren’t a lot of resources for this, so I thought I’d share!
For most people, it probably makes sense to use a graphical video editor, such as KDEnlive, OpenShot or Pitivi. I tried the latter two and found them sufficiently crashy that I was unable to get a video out of them that I could play back. This might be a result of my total lack of knowledge of, and respect for, containers, codecs, and … really whatever else I needed to know and didn’t. I presume the crashiness was me doing something wrong as I know that others do use these tools successfully.
I’m also a commandline sort of person. I have difficulty in using a pointing device for any length of time, and I found that I was able to capture the videos tightly enough that I just needed to glue them together rather than actually edit.
Ffmpeg is a commandline linux tool that is the biggest swiss army knife of video tools you have ever seen. There’s just one problem: on ubuntu, the program called ffmpeg is actually an alias for avconv, which is a fork of ffmpeg that is missing some key elements, such as the ability to concatenate videos. The upshot of which is that I downloaded and compiled my own copy of ffmpeg for this project. Once I had that, things got easier :)
I used this guide to get my ffmpeg tool and all the dependencies set up: https://trac.ffmpeg.org/wiki/UbuntuCompilationGuide
Ffprobe is a tool that looks at a video file and gives information about it. One thing that I found about combining videos is that matching resolutions and encodings are really important – sometimes you can create what looks like a valid output file, only to have it unable to play in some players. To use it:
ffprobe video.mp4
I found this very useful, so I thought I’d add a note about it here. I tested my videos in VLC, it seems a bit less tolerant than the standard gnome player, so it was a good way to check if the videos would play. There’s also a simpler version of VLC that shows fewer controls: cvlc (I found it handy).
Once I had the genuine version of ffmpeg compiled, I used that to combine my videos. First of all, I created an input file which contained a list of videos. Here’s an example of my
input.txt
file:
file 'wireshark1.mp4' file 'wireshark2.mp4' file 'wireshark3.mp4' file 'wireshark4.mp4' file 'wireshark5.mp4' file 'wireshark6.mp4' file 'wireshark7.mp4'
(can you guess what this was a video of?)
Then I used the following command to use this input file and create a resulting video of these videos played one after another:
./ffmpeg -f concat -i input.txt -c copy wireshark-demo.mp4
This can look successful and still produce a bit of a strange video if all your video files aren’t precisely the same resolution and format, but I was able to get results pretty quickly once I knew I had to get those things right in recording. The time spent planning the videos paid back several times over, as it was easy to just recapture one piece of the sequence if the need arose.
Ffmpeg is a beast, powerful but superbly complex, and it was tough going to find the commands I needed even without the “wrong” fork of the project being the default with ubuntu! Hopefully this post will remind me next time what to do, and if it helps you too, then awesome :) Feel free to leave additional tips and tricks in the comments.
My swiss army knife of document formats is a program called pandoc. It’s absolutely fabulous, powerful, and not too complicated if you don’t need to do anything too complicated. It will guess input and output formats from file extensions, or you can be more specific if you need to. Today’s command looks like this:
pandoc article.md -o article.html
You won’t be surprised to hear that this command takes a file called article.md which contains my markdown, and outputs a file called article.html containing the HTML. I also use this to convert between all the various text markups, HTML, but also PDF and office document formats – it’s a very comprehensive tool!
On an ubuntu platform, I’ve had a few false starts with video over the years, and mostly avoided it. But now my “Debugging HTTP” talk really does make more sense if you can see the process of something broken, what the tools show, and how to understand that information and fix the problem.
