Filters (#289)

* Framerate fix

Keep original framerate up to 60fps, halve any framerate above 60fps. Because of "video_frame_rate": Fraction(video_info["r_frame_rate"]), it does not work, when float used, the video is encoded but framerate suffers from rounding error.

* Framerate fix

Keep original framerate up to 60fps, halve any framerate above 60fps. Because of "video_frame_rate": Fraction(video_info["r_frame_rate"]), it does not work, when float used, the video is encoded but framerate suffers from rounding error.

* Introduction of minimum bitrate modifier

A minimum bitrate modifier introduced as per https://developers.google.com/media/vp9/settings/vod

* Introduction of minimum bitrate modifier

A minimum bitrate modifier introduced as per https://developers.google.com/media/vp9/settings/vod

* Deinterlacing and better filter logic

files/helpers.py

@@ -244,6 +244,7 @@ def media_file_info(input_file):
     - `video_bitrate`: Bitrate of the video stream in kBit/s
     - `video_width`: Width in pixels
     - `video_height`: Height in pixels
+    - `interlaced` : True if the video is interlaced
     - `video_codec`: Video codec
     - `audio_duration`: Duration of the audio in `s.msec`
     - `audio_sample_rate`: Audio sample rate in Hz
@@ -374,6 +375,10 @@ def media_file_info(input_file):
         video_frame_rate_n = video_frame_rate[0]
         video_frame_rate_d = video_frame_rate[2]
 
+    interlaced = False
+    if video_info.get("field_order") in ("tt", "tb", "bt", "bb"):
+        interlaced = True
+
     ret = {
         "filename": input_file,
         "file_size": file_size,
@@ -390,7 +395,7 @@ def media_file_info(input_file):
         "color_space": video_info.get("color_space"),
         "color_transfer": video_info.get("color_space"),
         "color_primaries": video_info.get("color_primaries"),
-        "field_order": video_info.get("field_order"),
+        "interlaced": interlaced,
         "display_aspect_ratio": video_info.get("display_aspect_ratio"),
         "sample_aspect_ratio": video_info.get("sample_aspect_ratio"),
     }
@@ -490,6 +495,7 @@ def get_base_ffmpeg_command(
     encoder,
     audio_encoder,
     target_fps,
+    interlaced,
     target_height,
     target_rate,
     target_rate_audio,
@@ -508,6 +514,7 @@ def get_base_ffmpeg_command(
         encoder {str} -- video encoder
         audio_encoder {str} -- audio encoder
         target_fps {fractions.Fraction} -- target FPS
+        interlaced {bool} -- true if interlaced
         target_height {int} -- height
         target_rate {int} -- target bitrate in kbps
         target_rate_audio {int} -- audio target bitrate
@@ -523,6 +530,27 @@ def get_base_ffmpeg_command(
     if target_fps < 1:
         target_fps = 1
 
+    filters = []
+
+    if interlaced:
+        filters.append("yadif")
+
+    target_width = round(target_height * 16 / 9)
+    scale_filter_opts = [
+        f"if(lt(iw\\,ih)\\,{target_height}\\,{target_width})",
+        f"if(lt(iw\\,ih)\\,{target_width}\\,{target_height})",
+        "force_original_aspect_ratio=decrease",
+        "force_divisible_by=2",
+        "flags=lanczos",
+    ]
+    scale_filter_str = "scale=" + ":".join(scale_filter_opts)
+    filters.append(scale_filter_str)
+
+    fps_str = f"fps=fps={target_fps}"
+    filters.append(fps_str)
+
+    filters_str = ",".join(filters)
+
     base_cmd = [
         settings.FFMPEG_COMMAND,
         "-y",
@@ -531,9 +559,7 @@ def get_base_ffmpeg_command(
         "-c:v",
         encoder,
         "-filter:v",
-        "scale=-2:" + str(target_height) + ",fps=fps=" + str(target_fps),
-        # always convert to 4:2:0 -- FIXME: this could be also 4:2:2
-        # but compatibility will suffer
+        filters_str,
         "-pix_fmt",
         "yuv420p",
     ]
@@ -716,6 +742,8 @@ def produce_ffmpeg_commands(media_file, media_info, resolution, codec, output_fi
     elif enc_type == "crf":
         passes = [2]
 
+    interlaced = media_info.get("interlaced")
+
     cmds = []
     for pass_number in passes:
         cmds.append(
@@ -727,6 +755,7 @@ def produce_ffmpeg_commands(media_file, media_info, resolution, codec, output_fi
                 encoder=encoder,
                 audio_encoder=AUDIO_ENCODERS[codec],
                 target_fps=target_fps,
+                interlaced=interlaced,
                 target_height=resolution,
                 target_rate=target_rate,
                 target_rate_audio=AUDIO_BITRATES[codec],