There are various parameters that control the behaviour of the animation, such as time interval, maximum number of animation frames, height and width, etc.

library(animation)
## see the first example in help(animation) on how to set and
## restore animation options

## use the PDF device: remember to set 'ani.type' accordingly
ani.options(ani.dev = "pdf", ani.type = "pdf", ani.height = 5, 
  ani.width = 7)

## use the Cairo PDF device if (require('Cairo')) {
## ani.options(ani.dev = CairoPDF, ani.type = 'pdf',
## ani.height = 6, ani.width = 6) }

## don't loop for GIF/HTML animations
ani.options(loop = FALSE)

## don't try to open the output automatically
ani.options(autobrowse = FALSE)

## it's a good habit to restore the options in the end so that
## other code will not be affected


## how to make use of the hidden option 'img.fmt'
saveHTML(expr = {
  png(ani.options("img.fmt"))
  for (i in 1:5) plot(runif(10))
  dev.off()
}, img.name = "custom_plot", use.dev = FALSE, ani.type = "png", 
  description = "Note how we use our own graphics device in 'expr'.", 
  htmlfile = "custom_device.html")