jsonclips.py - generate highlights based on JSON

usage: jsonclips.py clips.json

JSON file can specify:
    - output filename
    - source filepath
    - start time
    - duration
    - transition type [default: luma]
    - transition duration [default: 30]

jsonclips.py

@@ -0,0 +1,113 @@
+#!/bin/python
+"""jsonclips.py - generate highlights based on JSON
+
+usage: jsonclips.py clips.json
+
+JSON file can specify:
+    - output filename
+    - source filepath
+    - start time
+    - duration
+    - transition type [default: luma]
+    - transition duration [default: 30]
+"""
+
+DEFAULT_TRANSITION_DURATION = 30  # 30 frames, ie 0.5s at 60FPS
+DEFAULT_TRANSITION_TYPE = "luma"
+
+
+def process_highlights(jsonfile):
+    """Go through highlights, make clips, join to a video"""
+    import tempfile
+
+    def make_clips(sources=None, outputdir=None):
+        """Use ffmpeg to create output from processed JSON"""
+        import subprocess
+        import os
+
+        ffmpeg_common_args = ["ffmpeg", "-loglevel", "quiet", "-hide_banner"]
+        clipnum = 0
+
+        for source in sources:
+            print("Making {}s clip from {} at {}".format(
+                source["duration"], source["filepath"], source["time"]))
+
+            ffmpeg_file_args = ["-ss", str(source["time"]),
+                                "-i", source["filepath"],
+                                "-t", str(source["duration"]),
+                                "-c", "copy",
+                                os.path.join(outputdir,
+                                             "clip{}.mkv".format(clipnum))]
+
+            ffmpeg_args = ffmpeg_common_args + ffmpeg_file_args
+            print("Running ffmpeg with args:\n\n{}".
+                  format(ffmpeg_args))
+            subprocess.run(ffmpeg_args)
+
+            clipnum += 1
+
+    def make_output(workingdir=None, outputfile=None, numsources=None):
+        """Use MLT (melt) to join clips"""
+        import subprocess
+        import os
+
+        melt_args = ["melt"]
+
+        for i in range(numsources):
+            if i == 0:
+                melt_args.extend([os.path.join(workingdir, "clip{}.mkv"
+                                               .format(i))])
+            else:
+                melt_args.extend([
+                    os.path.join(workingdir, "clip{}.mkv".format(i)),
+                    "-mix", str(DEFAULT_TRANSITION_DURATION),
+                    "-mixer", str(DEFAULT_TRANSITION_TYPE)])
+
+        melt_args.extend(["-consumer", "avformat:{}".format(outputfile),
+                          "crf=20"])
+
+        print("Running melt with args:\n\n{}".format(melt_args))
+        subprocess.run(melt_args)
+
+    def parse_json(jsonfile=None):
+        """Parse global / per--clip options from jsonfile
+
+        Requires:
+            - outputfile
+            - list of sources
+        """
+        import json
+        import sys
+
+        if jsonfile:
+            with open(jsonfile, "r") as fh:
+                json_in = json.load(fh)
+
+        if "outputfile" not in json_in:
+            print("Please specify an outputfile to write to")
+            sys.exit(1)
+
+        if "sources" not in json_in:
+            print("Please specify some sources to process")
+            sys.exit(1)
+
+        return json_in
+
+    # Start
+
+    if jsonfile:
+        json_in = parse_json(jsonfile)
+
+    # in temporary dir
+    with tempfile.TemporaryDirectory() as tmpdir:
+        # make clips
+        make_clips(sources=json_in["sources"], outputdir=tmpdir)
+        # join clips using melt
+        make_output(workingdir=tmpdir, outputfile=json_in["outputfile"],
+                    numsources=len(json_in["sources"]))
+
+
+if __name__ == "__main__":
+    import sys
+
+    process_highlights(sys.argv[1])