Encode audio using libopus instead of aac

opus in mp4 is supported by modern versions of ffmpeg, as well as
YouTube upload. libopus is known to have good audio quality, while
FFmpeg's built-in AAC encoder is slow and low-quality (especially on
older ffmpeg versions)

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## 0.11.0 (unreleased)
 
+### Major Changes
+
+- Encode audio using libopus instead of aac (#487)
+
 ## 0.10.1
 
 ### Changelog

corrscope/outputs.py

@@ -247,7 +247,7 @@ class FFmpegOutputConfig(IOutputConfig):
         "-color_range 1 -colorspace bt709 -color_trc bt709 -color_primaries bt709 "
         "-movflags faststart"
     )
-    audio_template: str = "-c:a aac -b:a 384k"
+    audio_template: str = "-c:a libopus -b:a 256k"
 
 
 FFMPEG = "ffmpeg"