Merge pull request #170 from openzim/videos_vp9

webm video presets: migrate from VP8 to VP9 for smaller ZIMs

Author: benoit74

CHANGELOG.md

@@ -8,6 +8,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Changed
+
+- Migrate the **VideoWebmLow** and **VideoWebmHigh** presets to VP9 for smaller file size #79
+  - New preset versions are v3 and v2 respectively
 - Simplify type annotations by replacing Union and Optional with pipe character ("|") for improved readability and clarity
 
 ### Fixed

src/zimscraperlib/video/presets.py

@@ -37,21 +37,23 @@ class VideoWebmLow(Config):
     128k target video bitrate but stay within quality boundaries.
     48k audio bitrate"""
 
-    VERSION = 2
+    VERSION = 3
 
     ext = "webm"
     mimetype = f"{preset_type}/webm"
 
     options: ClassVar[dict[str, str | bool | int | None]] = {
-        "-codec:v": "libvpx",  # video codec
-        "-quality": "best",  # codec preset
-        "-b:v": "128k",  # Adjust quantizer within min/max to target this bitrate
-        "-qmin": "18",  # Reduce the bitrate on very still videos
+        "-codec:v": "libvpx-vp9",  # video codec
+        "-b:v": "140k",  # Adjust quantizer within min/max to target this bitrate
+        "-qmin": "30",  # Reduce the bitrate on very still videos
         "-qmax": "40",  # Increase the bitrate on very busy videos
+        "-g": "240",  # Number of frames allowed between keyframes
+        "-quality": "good",  # codec preset
+        "-speed": "4",  # Encoding speed (compromise between quality and encoding time)
         "-vf": "scale='480:trunc(ow/a/2)*2'",  # frame size
         "-codec:a": "libvorbis",  # audio codec
-        "-ar": "44100",  # audio sampling rate
         "-b:a": "48k",  # target audio bitrate
+        "-ar": "44100",  # audio sampling rate
     }
 
 
@@ -88,16 +90,22 @@ class VideoWebmHigh(Config):
 
     25 constant quality"""
 
-    VERSION = 1
+    VERSION = 2
 
     ext = "webm"
     mimetype = f"{preset_type}/webm"
 
     options: ClassVar[dict[str, str | bool | int | None]] = {
-        "-codec:v": "libvpx",  # video codec
+        "-codec:v": "libvpx-vp9",  # video codec
+        "-b:v": "340k",  # Adjust quantizer within min/max to target this bitrate
+        "-qmin": "26",  # Reduce the bitrate on very still videos
+        "-qmax": "54",  # Increase the bitrate on very busy videos
+        "-g": "240",  # Number of frames allowed between keyframes
+        "-quality": "good",  # codec preset
+        "-speed": "1",  # Encoding speed (compromise between quality and encoding time)
         "-codec:a": "libvorbis",  # audio codec
-        "-crf": "25",  # constant quality, lower value gives better qual and larger size
-        "-b:v": "0",  # must be passed if using constant quality mode via -cbr for codec
+        "-b:a": "48k",  # target audio bitrate
+        "-ar": "44100",  # audio sampling rate
     }
 
 

tests/video/test_video.py

@@ -151,19 +151,21 @@ def test_preset_has_mime_and_ext():
 
 def test_preset_video_webm_low():
     config = VideoWebmLow()
-    assert config.VERSION == 2
+    assert config.VERSION == 3
     args = config.to_ffmpeg_args()
-    assert len(args) == 20
+    assert len(args) == 24
     options_map = [
-        ("codec:v", "libvpx"),
+        ("codec:v", "libvpx-vp9"),
         ("codec:a", "libvorbis"),
-        ("b:v", "128k"),
+        ("b:v", "140k"),
         ("ar", "44100"),
         ("b:a", "48k"),
-        ("quality", "best"),
-        ("qmin", "18"),
+        ("quality", "good"),
+        ("qmin", "30"),
         ("qmax", "40"),
         ("vf", "scale='480:trunc(ow/a/2)*2'"),
+        ("g", "240"),
+        ("speed", "4"),
     ]
     for option, val in options_map:
         idx = args.index(f"-{option}")
@@ -172,35 +174,41 @@ def test_preset_video_webm_low():
 
     # test updating values
     config = VideoWebmLow(**{"-ar": "50000"})
-    config["-bufsize"] = "900k"
+    config["-qmin"] = "25"
     args = config.to_ffmpeg_args()
     idx = args.index("-ar")
     assert idx != -1 and args[idx + 1] == "50000"
-    idx = args.index("-bufsize")
-    assert idx != -1 and args[idx + 1] == "900k"
+    idx = args.index("-qmin")
+    assert idx != -1 and args[idx + 1] == "25"
 
 
 def test_preset_video_webm_high():
     config = VideoWebmHigh()
-    assert config.VERSION == 1
+    assert config.VERSION == 2
     args = config.to_ffmpeg_args()
-    assert len(args) == 10
+    assert len(args) == 22
     options_map = [
-        ("codec:v", "libvpx"),
+        ("codec:v", "libvpx-vp9"),
         ("codec:a", "libvorbis"),
-        ("b:v", "0"),
-        ("crf", "25"),
+        ("b:v", "340k"),
+        ("ar", "44100"),
+        ("b:a", "48k"),
+        ("quality", "good"),
+        ("qmin", "26"),
+        ("qmax", "54"),
+        ("g", "240"),
+        ("speed", "1"),
     ]
     for option, val in options_map:
         idx = args.index(f"-{option}")
         assert idx != -1
         assert args[idx + 1] == val
 
     # test updating values
-    config = VideoWebmHigh(**{"-crf": "51"})
+    config = VideoWebmHigh(**{"-qmax": "51"})
     config["-b:v"] = "300k"
     args = config.to_ffmpeg_args()
-    idx = args.index("-crf")
+    idx = args.index("-qmax")
     assert idx != -1 and args[idx + 1] == "51"
     idx = args.index("-b:v")
     assert idx != -1 and args[idx + 1] == "300k"
@@ -314,7 +322,7 @@ def test_preset_voice_mp3_low():
             "video.mp4",
             "video.webm",
             VideoWebmLow().to_ffmpeg_args(),
-            {"codecs": ["vp8", "vorbis"], "duration": 2},
+            {"codecs": ["vp9", "vorbis"], "duration": 2},
         ),
         (
             "video.webm",