Convert a sequence of images to a video by FFmpeg

Yihui Xie & Lijia Yu 2017-04-04

This function opens a graphics device to record the images produced in the code expr, then uses FFmpeg to convert these images to a video.

This function uses system to call FFmpeg to convert the images to a single video. The command line used in this function is: ffmpeg -y -r <1/interval> -i <>\%d.<ani.type> other.opts

where interval comes from ani.options('interval'), and ani.type is from ani.options('ani.type'). For more details on the numerous options of FFmpeg, please see the reference.

Some linux systems may use the alternate software ‘avconv’ instead of ‘ffmpeg’. The package will attempt to determine which command is present and set ani.options('ffmpeg') to an appropriate default value. This can be overridden by passing in the ffmpeg argument.

oopts = if (.Platform$OS.type == "windows") {
  ani.options(ffmpeg = "D:/Installer/ffmpeg/bin/ffmpeg.exe")
## usually Linux users do not need to worry about the ffmpeg path as long as
## FFmpeg or avconv has been installed

  par(mar = c(3, 3, 1, 0.5), mgp = c(2, 0.5, 0), tcl = -0.3, cex.axis = 0.8, cex.lab = 0.8,
    cex.main = 1)
  ani.options(interval = 0.05, nmax = 300)
  brownian.motion(pch = 21, cex = 5, col = "red", bg = "yellow")
}, = "BM.mp4", other.opts = "-pix_fmt yuv420p -b 300k")
# higher bitrate, better quality