media: Add matroska chapters to opus

docs/media/index.md

@@ -22,6 +22,13 @@
     :::shell
     parec [ -d DEVICE ] | flac --endian=little --channels=2 --bps=16 --sample-rate=48000 --sign=signed -o foo.flac -
 
+### Copy Matroska Chapters to Opus
+
+Requires the metadata to fit in one ogg page (so no cover art :().
+
+    :::shell
+    mkvextract file.mka chapters | xq -r 'def pad: tostring | (3 - length) as $l | ("0" * $l)[:$l] + .; [[.Chapters.EditionEntry.ChapterAtom[] | {start: .ChapterTimeStart, name: .ChapterDisplay.ChapterString}] | to_entries[] | "CHAPTER\(.key|pad)=\(.value.start)\nCHAPTER\(.key|pad)NAME=\(.value.name)"] | join("\n")' | opustags -i -S file.opus
+
 ## Video
 
 ### Copy DVD stream to file [with dvd already copied to local directory]