Making HiPERCAM movies

The makemovie command allows you to generate stills from a movie. It is a little painful to run and even more so to actually compile the stills into a movie, so this is just to provide an easy reminder.

Making the stills

makemovie can plot CCD images only or images plus a light curve if you have a reduce log file available. I would suggest that you either run it within an empty directory or create such a directory for directing the output since it will create one image per exposure. Start by creating just a few images and look at them with your favourite PNG viewer. You will need to spend a while tweaking things. The one thing that will change when you switch to a full run is the X-scale on the light curve plot since that is adjusted to fit the times of the images shown. You can adjust the apparent font size by altering the plot width and height, at the same time as the dpi to control the resolution. Crude, but it works. I haven’t got it working without rather a stack of “whitespace”; something for the future.

Here is a full listing of parameters I used to make a movie of the eclipsing double white dwarf ZTF J1539+5027. In this case I was in the directory containing the reduce log within which I had created an empty directory “tmp”. One up from the working directory was where the raw data, run0005.fits sat.

source = hl
run = ../run0005
first = 2
last = 1000
trim = False
ccd = 2
bias = bias3x3_slow.hcm
dark = none
flat = none
fmap = none
defect = none
log = run0005.log
targ = 1
comp = 2
ymin = 0.0
ymax = 0.05
ynorm = [1.0]
yoffset = [0.0]
location = e
fraction = 0.55
lpad = (0.15, 0.2, 0.1, 0.15)
cmap = viridis
width = 12.0
height = 3.0
dstore = tmp
ndigit = 4
fext = png
msub = False
iset = d
ilo = [0.0]
ihi = [100.0]
xlo = 0.0
xhi = 2048.0
ylo = 0.0
yhi = 1024.0
dpi = 200
style = dots
ms = 2.0

Making the movie from the stills

Once you have the stills, you still need to actually make the movie. I use the command ‘ffmpeg’ to do so like this:

ffmpeg -start_number 123 -i run0005_%04d.png -c:v libx264 -pix_fmt yuv420p movie.mp4 -y

which would find any files of the form ‘run0005_0340.png’ starting from ‘run0005_0123.png’. ‘ffmpeg’ has a million-and-one options and there be ways to tweak it, but this does a reasonable job I find. You can loop the movie with something like:

ffmpeg -start_number 3 -i run0011_%04d.png -filter_complex loop=5:362 -c:v libx264 -pix_fmt yuv420p movie.mp4 -y

which would add 6 loops.