Create video from sequence of still images

Stitch a sequence of images into a video animation. A simple wrapper for av::av_encode_video.

Usage

make_video(
  input_dir = getwd(),
  input_ext = ".png",
  output = "animation.mp4",
  duration = NULL,
  start_frame = 1,
  end_frame = NULL,
  size = NULL,
  overwrite = FALSE,
  verbose = FALSE,
  ...
)

Arguments

input_dir: directory containing images, default is working directory.
input_ext: character, file extension of images to be stitched into a video. All images must have same extension, width, and height. Each imaged will be positioned in the video in alphabetical order by image file name.
output: character, output video file name. See details.
duration: integer, output video duration in seconds. If NULL (default) then this will be determined by the number of input frames and the framerate (default is 24 frames per second). E.g., a video containing 240 frames at default 24 fps will be 10 seconds long. See details.
start_frame: integer, start frame. Defaults to start=1.
end_frame: integer, end frame. Defaults to end_frame = NULL (i.e., last frame).
size: integer vector with width and height of output video in pixels. Ignored if vfilter is passed via ....
overwrite: logical, overwrite existing output file? (default = FALSE)
verbose: logical, show output from av::av_encode_video? Default = FALSE.
...: optional arguments passed to av::av_encode_video. Such as framerate, vfilter, codec.

Value

One video animation will be written disk and the path and file name will be returned.

Details

This function was overhauled in glatos v 0.4.1 to simplify inputs and to no longer require an external program (ffmpeg.exe). As a result input arguments have changed, as described above. Starting with glatos v 0.7.0, any calls to make_video using the arguments from glatos v 0.4.0 or earlier will fail.

make_video is a simple wrapper of av::av_encode_video. It is intended to allow creation of videos from images (frames) created by glatos::make_frames as simple as possible. More advanced features of av, can be used by including any argument of av::av_encode_video in the call to make_video, or by calling av::av_encode_video directly. More information about the av package is available at https://cran.r-project.org/web/packages/av/index.html and https://docs.ropensci.org/av/.

A directory of sequenced image files (.png, .jpeg) are passed to input_dir argument. The input_ext argument specifies the type of files to be stitched into a video. The images passed to the function must all have the same size, height, and format.

Function can create .mp4, .mov, .mkv, .flv .wmv, or .mpeg animations. Format of created animation is determined by file extension of output.

If start_frame or end_frame are specified, then only frames within the specified range will be included in the output video.

If duration is specified, then the output framerate will be determined by the number of input frames and the framerate (default is 24 frames per second). E.g., a video of 10 second duration containing 240 frames will have an output frame rate of 24 fps. In some cases (when number of frames is small) the number of frames may not divide evently into the specified duration, so the output duration may differ from that specified. If the output frame rate exceeds 30 fps, then a warning will alert the user that some individual frame content may not be visible to users. Video duration may also be controlled by setting the framerate argument of av::av_encode_video. See ... above.

Author

Todd Hayden, Chris Holbrook

Examples

if (FALSE) { # \dontrun{

# load frames
frames <- system.file("extdata", "frames", package = "glatos")

# make .mp4 video
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation1.mp4")
)

# set duration to 10 seconds
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation2.mp4"),
  duration = 10
)

# set size of ouput video
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation3.mp4"),
  size = c(320, 240)
)

# start animation on frame 10, end on frame 20
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation_4.mp4"),
  start_frame = 10,
  end_frame = 20
)

# make move backwards- start animation of frame 20 and end on frame 10
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation_5.mp4"),
  start_frame = 20,
  end_frame = 10
)

# make .wmv video
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation1.wmv")
)


#--- Examples using more advanced features of av_encode_video

# resize output video by specifying a scale filter
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation_6.mp4"),
  vfilter = "scale=320:240"
)

# slow the video by 10 times
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation_7.mp4"),
  vfilter = "setpts=10*PTS"
)

# slow video by 10 times and scale to 320x240 resolution
make_video(
  input_dir = frames,
  input_ext = ".png",
  output = file.path(tempdir(), "animation_8.mp4"),
  vfilter = "scale=320:240, setpts=10*PTS"
)
} # }