Tag Archives: video

HTTP/2 in April 2016

On April 12 I had the pleasure of doing another talk in the Google Tech Talk series arranged in the Google Stockholm offices. I had given it the title “HTTP/2 is upon us, and here’s what you need to know about it.” in the invitation.

The room seated 70 persons but we had the amazing amount of over 300 people in the waiting line who unfortunately didn’t manage to get a seat. To those, and to anyone else who cares, here’s the video recording of the event.

If you’ve seen me talk about HTTP/2 before, you might notice that I’ve refreshed the material somewhat since before.

Turn many pictures into a movie

Challenge: you have 90 pictures of various sizes, taken in different formats and shapes. Using all sorts strange file names. Make a movie out of all of them, with the images using the correct aspect ratio. And add music. Use only command line tools on Linux.

Solution: this is a solution, you can most likely solve this in 22 other ways as well. And by posting it here, I can find it myself if I ever want to do the same stunt again…


# convert options
pic="-resize 1920x1080 -background black -gravity center -extent 1920x1080"

# loop over the images
for i in `ls *jpg | sort -R`; do
 echo "Convert $i"
 convert $pic $i "pic-$j.jpg"
 j=`expr $j + 1`

# now generate the movie
echo "make movie"
ffmpeg -framerate 3 -i pic-%d.jpg -i $mp3 -acodec copy -c:v libx264 -r 30 -pix_fmt yuv420p -s 1920x1080 -shortest out.mp4


This is a shell script.

The ‘pic’ variable holds command line options for the ImageMagick ‘convert‘ tool. It resizes each picture to 1920×1080 while maintaining aspect ratio and if the pic gets smaller, it is centered and gets a black border.

The loop goes through all files matching *,jpg, randomizes the order with ‘sort’ and then runs ‘convert’ on them one by one and calls the output files pic-[number].jpg where number is increased by one for each image.

Once all images have the correct and same size, ‘ffmpeg‘ is invoked. It is told to produce a movie with 3 photos per second, how to find all the images, to include an mp3 file into the output and to stop encoding when one of the streams ends – this assumes the playing time of the mp3 file is longer than the total time the images are shown so the movie stops when we run out of images to show.


The ‘out.mp4’ file, uploaded to youtube could then look like this:

(music by Bensound.com)

daniel weekly 42, switching off Nagle


See you at ApacheCon on Friday!


14% HTTP/2 thanks to nginx ?

Brotli everywhere! Firefox, libbrotli

The –libcurl flaw is fixed (and it was GONE from github for a few hours)

http2 explained in Swedish

No, the cheat sheet cannot be in the man page. But…

bug of the week: the http/2 performance fix


option of the week: -k

Talking at the GOTO Conference next week

daniel weekly 41, now in markdown

Episode 41, just out:


me on kodsnack

115 days with RFC

http2 explained in markdown, translations. Swedish?

The curl google tech talk

curl -X

the curl and wget war

curl vs Wget

a curl cheat sheet

curl feature freeze period, release october 7

ApacheCon, October 2

Bug of the week: Downloading a long sequence of URLs results in high CPU usage and slowness

Option of the week: -O

daniel weekly

daniel weekly screenshot

My series of weekly videos, in lack of a better name called daniel weekly, reached episode 35 today. I’m celebrating this fact by also adding an RSS-feed for those of you who prefer to listen to me in an audio-only version.

As an avid podcast listener myself, I can certainly see how this will be a better fit to some. Most of these videos are just me talking anyway so losing the visual shouldn’t be much of a problem.

A typical episode

I talk about what I work on in my open source projects, which means a lot of curl stuff and occasional stuff from my work on Firefox for Mozilla. I also tend to mention events I attend and HTTP/networking developments I find interesting and grab my attention. Lots of HTTP/2 talk for example. I only ever express my own personal opinions.

It is generally an extremely geeky and technical video series.

Every week I mention a (curl) “bug of the week” that allows me to joke or rant about the bug in question or just mention what it is about. In episode 31 I started my “command line options of the week” series in which I explain one or a few curl command line options with some amount of detail. There are over 170 options so the series is bound to continue for a while. I’ve explained ten options so far.

I’ve set a limit for myself and I make an effort to keep the episodes shorter than 20 minutes. I’ve not succeed every time.


The 35 episodes have been viewed over 17,000 times in total. Episode two is the most watched individual one with almost 1,500 views.

Right now, my channel has 190 subscribers.

The top-3 countries that watch my videos: USA, Sweden and UK.

Share of viewers that are female: 3.7%

daniel.haxx.se episode 8

Today I hesitated to make my new weekly video episode. I looked at the viewers number and how they basically have dwindled the last few weeks. I’m not making this video series interesting enough for a very large crowd of people. I’m re-evaluating if I should do them at all, or if I can do something to spice them up…

… or perhaps just not look at the viewers numbers at all and just do what think is fun?

I decided I’ll go with the latter for now. After all, I enjoy making these and they usually give me some interesting feedback and discussions even if the numbers are really low. What good is a number anyway?

This week’s episode:






  • I’m offering two talks for FOSDEM


  • release next Wednesday
  • bug fixing period
  • security advisory is pending


daniel.haxx.se week #3

I won’t keep posting every video update here, but I mostly wanted to mention that I’ve kept posting a weekly video over at youtube basically explaining what’s going on right now within my dearest projects. Mostly curl and some Firefox stuff.

This week: libcurl server cert verification API got a bashing at SEC-T, is HTTP for UDP a good idea? How about adding HTTP cache support to libcurl? HTTP/2 is getting deployed as we speak. Interesting curl bug when used by XBMC. The patch series for Firefox bug 939318 is improving slowly – will it ever land?

Video perhaps?

I decided to try to do a short video about my current work right now and make it available for you all. I try to keep it short (5-7 minutes) and I’m certainly no pro at it, but I will try to make a weekly one for a while and see if it gets any fun. I’m going to read your comments and responses to this very eagerly and that will help me decide how I will proceed on this experiment.