fix(ffmpeg): raise if time for thumbnail generation is invalid

CHANGELOG

@@ -1,6 +1,14 @@
 CHANGELOG
 =======
 
+0.4.0 (04.12.2018)
+----------
+
+* Change: An `InvalidTimeError` is raise, when a thumbnail could not be generated
+  * This can happens if the chosen time is too close to the end of the video
+    or if the video is shorter.
+
+
 0.3.1 (16.11.2018)
 ----------
 

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "django-video-encoding"
-version = "0.3.1"
+version = "0.4.0"
 description = "django-video-encoding helps to convert your videos into different formats and resolutions."
 authors = ["Alexander Frenzel <alex@relatedworks.com>"]
 

test_proj/media_library/tests/test_ffmpeg_backend.py

@@ -1,8 +1,10 @@
 import os
 import tempfile
 
+import pytest
 from PIL import Image
 
+from video_encoding import exceptions
 from video_encoding.backends.ffmpeg import FFmpegBackend
 
 
@@ -46,6 +48,27 @@ def test_get_thumbnail(ffmpeg, video_path):
         assert height == 720
 
 
+def test_get_thumbnail__invalid_time(ffmpeg, video_path):
+    with pytest.raises(exceptions.InvalidTimeError):
+        ffmpeg.get_thumbnail(video_path, at_time=1000000)
+
+
+@pytest.mark.parametrize(
+    'offset', (0, 0.02),
+)
+def test_get_thumbnail__too_close_to_the_end(ffmpeg, video_path, offset):
+    """
+    If the selected time point is close to the end of the video,
+    a video frame cannot be extracted.
+    """
+    duration = ffmpeg.get_media_info(video_path)['duration']
+
+    with pytest.raises(exceptions.InvalidTimeError):
+        ffmpeg.get_thumbnail(
+            video_path, at_time=duration - offset,
+        )
+
+
 def test_check():
     assert FFmpegBackend.check() == []
 

video_encoding/backends/base.py

@@ -30,5 +30,8 @@ def get_media_info(self, video_path):  # pragma: no cover
     def get_thumbnail(self, video_path):  # pragma: no cover
         """
         Extracts an image of a video and returns its path.
+
+        If the requested thumbnail is not within the duration of the video
+        an `InvalidTimeError` is thrown.
         """
         pass

video_encoding/backends/ffmpeg.py

@@ -9,9 +9,9 @@
 import six
 from django.core import checks
 
+from .. import exceptions
 from ..compat import which
 from ..config import settings
-from ..exceptions import FFmpegError
 from .base import BaseEncodingBackend
 
 logger = logging.getLogger(__name__)
@@ -39,19 +39,19 @@ def __init__(self):
             settings, 'VIDEO_ENCODING_FFPROBE_PATH', which('ffprobe'))
 
         if not self.ffmpeg_path:
-            raise FFmpegError("ffmpeg binary not found: {}".format(
+            raise exceptions.FFmpegError("ffmpeg binary not found: {}".format(
                 self.ffmpeg_path or ''))
 
         if not self.ffprobe_path:
-            raise FFmpegError("ffprobe binary not found: {}".format(
+            raise exceptions.FFmpegError("ffprobe binary not found: {}".format(
                 self.ffmpeg_path or ''))
 
     @classmethod
     def check(cls):
         errors = super(FFmpegBackend, cls).check()
         try:
             FFmpegBackend()
-        except FFmpegError as e:
+        except exceptions.FFmpegError as e:
             errors.append(checks.Error(
                 e.msg,
                 hint="Please install ffmpeg.",
@@ -69,12 +69,12 @@ def _spawn(self, cmds):
             )
         except OSError as e:
             raise six.raise_from(
-                FFmpegError('Error while running ffmpeg binary'), e)
+                exceptions.FFmpegError('Error while running ffmpeg binary'), e)
 
     def _check_returncode(self, process):
         stdout, stderr = process.communicate()
         if process.returncode != 0:
-            raise FFmpegError("`{}` exited with code {:d}".format(
+            raise exceptions.FFmpegError("`{}` exited with code {:d}".format(
                 ' '.join(process.args), process.returncode))
         self.stdout = stdout.decode(console_encoding)
         self.stderr = stderr.decode(console_encoding)
@@ -127,14 +127,14 @@ def encode(self, source_path, target_path, params):  # NOQA: C901
             yield percent
 
         if os.path.getsize(target_path) == 0:
-            raise FFmpegError("File size of generated file is 0")
+            raise exceptions.FFmpegError("File size of generated file is 0")
 
         # wait for process to exit
         self._check_returncode(process)
 
         logger.debug(output)
         if not output:
-            raise FFmpegError("No output from FFmpeg.")
+            raise exceptions.FFmpegError("No output from FFmpeg.")
 
         yield 100
 
@@ -171,18 +171,28 @@ def get_media_info(self, video_path):
     def get_thumbnail(self, video_path, at_time=0.5):
         """
         Extracts an image of a video and returns its path.
+
+        If the requested thumbnail is not within the duration of the video
+        an `InvalidTimeError` is thrown.
         """
         filename = os.path.basename(video_path)
         filename, __ = os.path.splitext(filename)
         _, image_path = tempfile.mkstemp(suffix='_{}.jpg'.format(filename))
 
         video_duration = self.get_media_info(video_path)['duration']
-        thumbnail_time = min(at_time, video_duration - 0.02)
+        if at_time > video_duration:
+            raise exceptions.InvalidTimeError()
+        thumbnail_time = at_time
 
         cmds = [self.ffmpeg_path, '-i', video_path, '-vframes', '1']
         cmds.extend(['-ss', str(thumbnail_time), '-y', image_path])
 
         process = self._spawn(cmds)
         self._check_returncode(process)
 
+        if not os.path.getsize(image_path):
+            # we somehow failed to generate thumbnail
+            os.unlink(image_path)
+            raise exceptions.InvalidTimeError()
+
         return image_path

video_encoding/exceptions.py

@@ -1,8 +1,12 @@
 class VideoEncodingError(Exception):
+    pass
+
+
+class FFmpegError(VideoEncodingError):
     def __init__(self, *args, **kwargs):
         self.msg = args[0]
         super(VideoEncodingError, self).__init__(*args, **kwargs)
 
 
-class FFmpegError(VideoEncodingError):
+class InvalidTimeError(VideoEncodingError):
     pass