Creating a Movie in PixInsight

May 23, 2015  •  Leave a Comment

I recently imaged a small asteroid (42251) for the purpose of calculating the value of AU, as well as generating an asteroid lightcurve. I imaged for 60 seconds every 10 minutes, for about 7 hours, and of course wanted to generate a movie of the asteroid movement. It turns out that this is fairly straightforward to do in PixInsight, with a few gotchas.

Start by opening the Blink Process in PI, and load all of the images that you want included in the movie. Then click the rightmost icon at the bottom of Blink, the one that looks like a movie clapper. You'll be presented with the Make Video dialog, with the following defaults:

 

There are a couple of things to note. One is that PI and Blink default to the use of the freely available ffmpeg video software, and I used ffmpeg for my movie. You can download ffmpeg from multiple locations, and for multiple Operating Systems. I work on a Mac with OS X, and ffmpeg installed and ran just fine.

Blink works by generating a sequential series of .png image files, which ffmpeg then loads and turns into a video sequence. The arguments to ffmpeg, as shown in the default above, probably work in some situations, but will not generate a valid QuickTime movie for the Mac. I wanted to embed my video in a Keynote presentation, so needed to create a Quicktime compatible video.

After a lot of trial and error, and googling around, I came up with the following ffmpeg arguments that resulted in a valid video:

-i Blink%05d.png  -crf 34 -preset medium -filter:v "setpts=2.0*PTS" -c:v libx264  -pix_fmt yuv420p -y  A42251.mov

Some of the changes are to rename the output movie, and to stretch the movie to run more slowly (the setpts option). The crucial changes are to specify the libx264 video codec, the yuv420p video format, and the "-crf 34" quality factor to reduce the size of the generated video, so that it can run smoothly in Keynote. You can experiment with tweaking these settings for your particular application, but these settings should get you close.

 

 


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