FFglitch 0.9.4 released

FFglitch 0.9.4 has been released.

Python3

The main change in this version is the addition of python3 scripting support. This way you don’t need to use the old three-step method of export/glitch/apply for your Python scripts anymore. It can all be done in one go, just like it was already possible with javascript since version 0.9.1.

For example, the Simple motion vector tutorial in python3 would be:

def glitch_frame(frame):
    # bail out if we have no motion vectors
    if not "mv" in frame:
        return
    # bail out if we have no forward motion vectors
    if not "forward" in frame["mv"]:
        return
    fwd_mvs = frame["mv"]["forward"]

    # loop through all rows
    for row in fwd_mvs:
        # loop through all macroblocks
        for mv in row:
            # clear horizontal element of all motion vectors

            # THIS IS WHERE THE MAGIC HAPPENS

            mv[0] = 0; # this sets the horizontal motion vector to zero
            # mv[1] = 0; # you could also change the vertical motion vector

$ ./ffedit -i temp_file.mpg -f mv -s mv_sink_and_rise.py -o glitched_file.mpg

NOTE: You have to install Python3 yourself! Get it from their website: https://www.python.org/downloads/.

Script video filter

A script video filter has been added, supporting both JavaScript and Python, so that you can edit the pixels of a video programmatically. You can chain the filter on top of an existing video or create a video from scratch. For example, create this file named uv.py:

def filter(args):
  data = args["data"]
  # planes are [ Y, U, V ]
  for p, plane in enumerate(data):
    # skip plane Y
    if p == 0:
      continue
    # for planes U and V, draw a color plane
    for i, row in enumerate(plane):
      for j in range(len(row)):
        if p == 1:
          row[j] = j+j
        else:
          row[j] = 254-(i+i)

and then run it on top of the testsrc2 video source from FFmpeg:

$ ffgac -f lavfi -i "testsrc2=duration=10:size=256x256" -vf script="py=uv.py" -q 0 -y testsrc2_uv.mp4

and you’ll end up with this nice video:

Motion Vector Delta Feature

Motion vectors values are composed of a prediction part and a delta part, which is the value that is written to the bitstream.

A new feature named "mv_delta" has been added to ffedit, which allows you to fiddle with only those delta values for both MPEG-2 and MPEG-4.

There is no example for this feature for now. This is left as an exercise for the reader.

Motion Vector Overflow

There is now greater control on how ffedit should behave when it encounters an overflow in either the "mv" or the "mv_delta" features. Three more values are exported, namely "fcode", "bcode" and "overflow".

The first two are for information purposes only and allow you to calculate the min and max values for your motion vectors if you wish. For MPEG-2 the values go from -(1<<(fcode+3)) to (1<<(fcode+3))-1, and for MPEG-4 the values go from -(1<<(fcode+4)) to (1<<(fcode+4))-1, which, for an fcode of 1, would range from [-16, 15] for MPEG-2 and [-32, 31] for MPEG-4 (keep in mind that those are half-pel values).

The "overflow" field tells ffedit how to behave when it encounters an overflow while transplicating a file. The four possible values are as follows:

  frame["mv"]["overflow"] = "assert";   // quits ffedit on overflow
  frame["mv"]["overflow"] = "truncate"; // truncates values within range for given fcode
  frame["mv"]["overflow"] = "ignore";   // just ignore the overflow - same behaviour as versions before 0.9.4
  frame["mv"]["overflow"] = "warn";     // ignore, like above, but also write a warning message - new default behaviour

I’m too lazy to write an example for now. This is also left as an exercise for the reader.

ffglitch.js

A new executable called qjs (or qjs.exe for Windows) has been added to the release bundle, along with a new file ffglitch.js. qjs is the quickjs command-line interpreter. It can be used to test your .js scripts. ffglitch.js It works similarly to ffglitch.py, but for javascript files. To use it, run something like:

  $ ./qjs ffglitch.js -i mv.json -s mv_sink_and_rise.js -o mv_glitched.json

More changes

• Speedup exporting of JSON data by up to 40%
• Speedup importing of JSON data by up to 80%
• Added "macroblock" feature to MPEG-4 (works the same way as it did for MPEG-2)
• Fixed -dqt option for non-mjpeg (broken in 0.9.3)
• Updated quickjs to quickjs-2021-03-27

My build system has changed

I now have a mac mini running Mojave and I build the macos version there. If it doesn’t run on older versions of macos please let me know and I’ll try to figure out a way to fix it.

The linux build no longer uses musl, but is built on a CentOS 7 image, which should run correctly on most modern distros.

Get it in the Download page.