[postprocessor:ugoira] insert extra frame

into files generated with the 'image2' demuxer to compensate for the
last frame not being shown for as long as it should.

This only happens for ugoira with non-uniform delays between frames and
only when 'repeat-last-frame' is enabled.

gallery_dl/postprocessor/ugoira.py

@@ -10,12 +10,20 @@
 
 from .common import PostProcessor
 from .. import util
-import collections
 import subprocess
 import tempfile
 import zipfile
+import shutil
 import os
 
+try:
+    from math import gcd
+except ImportError:
+    def gcd(a, b):
+        while b:
+            a, b = b, a % b
+        return a
+
 
 class UgoiraPP(PostProcessor):
 
@@ -151,10 +159,26 @@ class UgoiraPP(PostProcessor):
 
     def _process_image2(self, pathfmt, tempdir):
         tempdir += "/"
+        frames = self._frames
+
+        # add extra frame if necessary
+        if self.repeat and not self._delay_is_uniform(frames):
+            last = frames[-1]
+            delay_gcd = self._delay_gcd(frames)
+            if last["delay"] - delay_gcd > 0:
+                last["delay"] -= delay_gcd
+
+                self.log.debug("non-uniform delays; inserting extra frame")
+                last_copy = last.copy()
+                frames.append(last_copy)
+                name, _, ext = last_copy["file"].rpartition(".")
+                last_copy["file"] = "{:>06}.{}".format(int(name)+1, ext)
+                shutil.copyfile(tempdir + last["file"],
+                                tempdir + last_copy["file"])
 
         # adjust frame mtime values
         ts = 0
-        for frame in self._frames:
+        for frame in frames:
             os.utime(tempdir + frame["file"], ns=(ts, ts))
             ts += frame["delay"] * 1000000
 
@@ -228,11 +252,26 @@ class UgoiraPP(PostProcessor):
             file.write("\n".join(content))
         return timecodes
 
+    def calculate_framerate(self, frames):
+        uniform = self._delay_is_uniform(frames)
+        if uniform:
+            return ("1000/{}".format(frames[0]["delay"]), None)
+        return (None, "1000/{}".format(self._delay_gcd(frames)))
+
     @staticmethod
-    def calculate_framerate(framelist):
+    def _delay_gcd(frames):
-        counter = collections.Counter(frame["delay"] for frame in framelist)
+        result = frames[0]["delay"]
-        fps = "1000/{}".format(min(counter))
+        for f in frames:
-        return (fps, None) if len(counter) == 1 else (None, fps)
+            result = gcd(result, f["delay"])
+        return result
+
+    @staticmethod
+    def _delay_is_uniform(frames):
+        delay = frames[0]["delay"]
+        for f in frames:
+            if f["delay"] != delay:
+                return False
+        return True
 
 
 __postprocessor__ = UgoiraPP