cut detection based on fps of source material

pandora/archive/cutdetection.py

@@ -0,0 +1,89 @@
+import subprocess
+
+import numpy as np
+import ox
+
+from django.config  import settings
+
+from .utils import AspectRatio
+
+def _get_distance(data0, data1):
+    diff = data0.astype(np.float32) - data1.astype(np.float32)
+    per_pixel_distance = np.linalg.norm(diff, axis=2)
+    total_distance = per_pixel_distance.sum()
+    num_pixels = data0.shape[0] * data0.shape[1]
+    max_distance = num_pixels * np.sqrt(3 * (255 ** 2))
+    return total_distance / max_distance
+
+def detect_cuts(path, seconds=True):
+    depth = 3
+    info = ox.avinfo(path)
+    dar = AspectRatio(info['video'][0]['display_aspect_ratio'])
+    fps = AspectRatio(info['video'][0]['framerate'])
+    height = 96
+    width = int(dar * height)
+    width += width % 2
+    nbytes = depth * width * height
+    bufsize = nbytes + 100
+    cmd = [
+        settings.FFMPEG,
+        '-hide_banner',
+        '-loglevel', 'error',
+        '-i', path,
+        '-threads', '4',
+        '-f', 'rawvideo',
+        '-pix_fmt', 'rgb24',
+        '-vcodec', 'rawvideo',
+        '-vf', 'scale=%d:%d' % (width, height),
+        '-aspect', '%d:%d' % (width, height),
+        '-'
+    ]
+    #print(' '.join(cmd))
+    p = subprocess.Popen(cmd,
+        bufsize=bufsize,
+        stdout=subprocess.PIPE,
+        close_fds=True)
+    first = True
+    previous_frame = None
+    cuts = []
+    detect_cuts = True
+    short_cut = None
+    cut_frames = []
+
+    frame_i = 0
+    previous_distance = 0
+
+    while True:
+        data = p.stdout.read(nbytes)
+        if len(data) != nbytes:
+            if first:
+                raise IOError("ERROR: could not open file %s" % path)
+            else:
+                break
+        else:
+            first = False
+            frame = np.frombuffer(data, dtype=np.uint8).reshape((height, width, depth))
+            frame_data = np.asarray(frame)
+            if frame_i == 0:
+                is_cut = False
+                previous_distance = 0
+            else:
+                if short_cut and frame_i - short_cut > 2:
+                    cuts.append(short_cut)
+                    short_cut = None
+                distance = _get_distance(previous_frame_data, frame_data)
+                is_cut = distance > 0.1 or (distance > 0.2 and abs(distance - previous_distance) > 0.2)
+                if is_cut:
+                    if frame_i - (0 if not cuts else short_cut or cuts[-1]) < 3:
+                        is_cut = False
+                        short_cut = frame_i
+                    else:
+                        cuts.append(frame_i)
+                previous_distance = distance
+            previous_frame_data = frame_data
+            frame_i += 1
+    if seconds:
+        return [float('%0.3f' % float(c/fps)) for c in cuts]
+    else:
+        return cuts
+

pandora/archive/extract.py

@@ -23,6 +23,7 @@ import pillow_avif
 from pillow_heif import register_heif_opener
 
 from .chop import Chop, make_keyframe_index
+from .utils import AspectRatio
 
 
 register_heif_opener()
@@ -33,28 +34,6 @@ img_extension = 'jpg'
 MAX_DISTANCE = math.sqrt(3 * pow(255, 2))
 
 
-class AspectRatio(fractions.Fraction):
-
-    def __new__(cls, numerator, denominator=None):
-        if not denominator:
-            ratio = list(map(int, numerator.split(':')))
-            if len(ratio) == 1:
-                ratio.append(1)
-            numerator = ratio[0]
-            denominator = ratio[1]
-            # if its close enough to the common aspect ratios rather use that
-            if abs(numerator/denominator - 4/3) < 0.03:
-                numerator = 4
-                denominator = 3
-            elif abs(numerator/denominator - 16/9) < 0.02:
-                numerator = 16
-                denominator = 9
-        return super(AspectRatio, cls).__new__(cls, numerator, denominator)
-
-    @property
-    def ratio(self):
-        return "%d:%d" % (self.numerator, self.denominator)
-
 def supported_formats():
     if not find_executable(settings.FFMPEG):
         return None

pandora/archive/utils.py

@@ -0,0 +1,25 @@
+import fractions
+import math
+
+class AspectRatio(fractions.Fraction):
+
+    def __new__(cls, numerator, denominator=None):
+        if not denominator:
+            ratio = list(map(int, numerator.split(':')))
+            if len(ratio) == 1:
+                ratio.append(1)
+            numerator = ratio[0]
+            denominator = ratio[1]
+            # if its close enough to the common aspect ratios rather use that
+            if abs(numerator/denominator - 4/3) < 0.03:
+                numerator = 4
+                denominator = 3
+            elif abs(numerator/denominator - 16/9) < 0.02:
+                numerator = 16
+                denominator = 9
+        return super(AspectRatio, cls).__new__(cls, numerator, denominator)
+
+    @property
+    def ratio(self):
+        return "%d:%d" % (self.numerator, self.denominator)
+