mirror of
https://git.pumpin.online/funkpower/catena.git
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110 lines
4.7 KiB
Bash
110 lines
4.7 KiB
Bash
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#!/bin/sh
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# A recording to chapter marks, citable passages, and a copy that plays.
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#
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# Takes the captions a video already carries, normalises them to one cue
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# stream, and turns that into chapter marks for a player and passages worth
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# embedding — each keeping the second it was said at. Then asks whether the
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# file itself would play on a phone, and prints the one ffmpeg call that
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# fixes it.
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#
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# examples/shell/02-video-to-chapters.sh [url] [work-dir]
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#
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# The default is a NASA upload: a work of the US government, so public
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# domain, and captioned by a person rather than by a model. Any URL yt-dlp
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# can reach works, and any local subtitle file works too — skip to the
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# cuenorm line and feed it your own.
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#
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# Needs jq, ffmpeg, and yt-dlp with impersonation support, which YouTube now
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# requires before it will hand over captions:
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#
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# pipx install "yt-dlp[default,curl-cffi]"
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#
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# and the catena commands on PATH.
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set -eu
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url="${1:-https://www.youtube.com/watch?v=h0wLZJeYGxw}"
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work="${2:-./work}"
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mkdir -p "$work"
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# Captions written by a person where there are any, and a model's otherwise.
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# Automatic captions roll — each line is re-sent as it scrolls up the screen —
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# so the same sentence arrives three times and every passage says it thrice.
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if [ -z "$(find "$work" -name '*.vtt' -print -quit 2>/dev/null)" ]; then
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echo "fetching captions"
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yt-dlp --skip-download --write-subs --sub-langs 'en.*' --sub-format vtt \
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--output "$work/%(id)s.%(ext)s" "$url" >/dev/null 2>&1 ||
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yt-dlp --skip-download --write-auto-subs --sub-langs 'en.*' --sub-format vtt \
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--output "$work/%(id)s.%(ext)s" "$url" >/dev/null
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fi
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# Where several tracks came back, the smallest is the written one: a rolling
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# track repeats every line and is four or five times the size.
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subs="$(find "$work" -name '*.vtt' -exec ls -S {} + | tail -1)"
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[ -n "$subs" ] || { echo "no captions on that video; try another URL" >&2; exit 1; }
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echo " captions: $(basename "$subs")"
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echo
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echo "== cues"
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cuenorm "$subs" > "$work/cues.ndjson"
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jq -s -r '" \(length) cues over \((map(.end) | max) / 60 | floor)m\((map(.end) | max) % 60 | floor)s"' "$work/cues.ndjson"
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jq -r '" [\(.start | floor)s] \(.text[0:62])"' "$work/cues.ndjson" | head -3
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# Where the subject changes, found from the words alone — no model, no
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# network. The titles come out of each chapter's own first sentence, and are
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# meant to be replaced by something better later.
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echo
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echo "== chapters"
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cueseg < "$work/cues.ndjson" > "$work/chapters.ndjson"
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jq -r '" \(.start | floor)s–\(.end | floor)s \(.title)"' "$work/chapters.ndjson"
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# Cues packed to a size worth embedding, each carrying the seconds it spans,
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# so a search hit can be played back at the moment it was said.
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echo
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echo "== passages"
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cuepack < "$work/cues.ndjson" > "$work/passages.ndjson"
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jq -s -r '" \(length) passages, \(map(.tokens) | add / length | floor) tokens on average"' "$work/passages.ndjson"
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jq -s -r '.[0] | " [\(.start_time | floor)s–\(.end_time | floor)s] \(.text[0:150])…"' "$work/passages.ndjson"
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echo
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echo "== chapter marks, as a player would take them"
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jq -r '"\(.start | floor) \(.title)"' "$work/chapters.ndjson" |
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awk '{ t = $1; $1 = ""; printf " %02d:%02d:%02d%s\n", t/3600, (t%3600)/60, t%60, $0 }'
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# And the file itself. A recording indexed but unplayable is half a job: a
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# phone will not open VP9 in a WebM container, whatever the transcript says.
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# Twenty seconds of it is enough to judge the streams, and spares the
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# download.
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echo
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echo "== would it play on a phone"
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video="$(find "$work" -type f \( -name '*.webm' -o -name '*.mkv' -o -name '*.mp4' \) -print -quit)"
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if [ -z "$video" ]; then
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echo " fetching twenty seconds of it"
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yt-dlp -f 'worstvideo[ext=webm]+worstaudio[ext=webm]/worst' \
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--download-sections '*0-20' --force-keyframes-at-cuts \
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--output "$work/%(id)s.%(ext)s" "$url" >/dev/null 2>&1 || true
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video="$(find "$work" -type f \( -name '*.webm' -o -name '*.mkv' -o -name '*.mp4' \) -print -quit)"
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fi
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[ -n "$video" ] || { echo " nothing to judge"; exit 0; }
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avplan --json "$video" | jq -r '
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" \(.streams.container): \(.streams.video) video, \(.streams.audio // "no") audio",
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(if .playable then " plays as it stands" else (.reasons[] | " · \(.)") end)'
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# Exit 0 means there is a plan to print; 1 means the file already plays. The
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# encoder is whatever this machine actually has — videotoolbox on a Mac,
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# NVENC or VAAPI on a Linux box, libx264 where there is no card. Nothing is
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# run: converting is expensive and irreversible enough to read first.
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echo
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if plan="$(avplan --output "$work/for-phone.mp4" "$video")"; then
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echo " the one call that fixes it:"
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echo
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printf ' %s\n' "$plan"
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echo
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echo " run it with: eval \"\$(avplan --output out.mp4 FILE)\""
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else
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echo " nothing to convert"
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fi
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echo
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echo "written to $work/"
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