X-Git-Url: https://code.delx.au/transcoding/blobdiff_plain/698521ee62495859c3dab544eac316a308d983c1..3a57980b8f4bdeafc34d1ef252e6d1017b8605a8:/fix-pal-speedup

diff --git a/fix-pal-speedup b/fix-pal-speedup
index 39c4ba4..4fb9dcb 100755
--- a/fix-pal-speedup
+++ b/fix-pal-speedup
@@ -1,80 +1,81 @@
-#!/bin/bash -e
+#!/bin/bash
 
 # Many DVDs released in Australia are sped up from 24fps to 25fps.
 # This script reverses the procedure, correcting the audio pitch.
-# The video framerate is adjusted without re-encoding. The audio is
-# slowed, volume normalised, down-mixed to stereo and encoded as mp3.
+# - The video framerate is adjusted without re-encoding.
+# - The audio is slowed, and encoded as AAC, preserving surround sound.
+# - Chapters and subtitles are also adjusted to match the new timing.
 
-if [ -z "$1" -o -z "$2" ]; then
-    echo "Usage: $0 destdir infile [infile ...]"
+if [ -z "$1" ] || [ -z "$2" ]; then
+    echo "Usage: $0 infile outfile"
     exit 1
 fi
 
-set -xe
-FORCEFPS="24"
-SLOWDOWN="0.96"
+set -o pipefail -eux
+OLDFPS="25"
+NEWFPS="24"
+SLOWFILTER=("-filter" "asetrate=46080,aresample=osr=48000:resampler=soxr")
 
-function mux_replace_audio {
-    infile="$1"
-    audiofile="$2"
-    outfile="$3"
+function main {
+    local infile="$1"
+    local outfile="$2"
 
-    trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
-    mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
-}
-
-function extract_audio {
-    infile="$1"
+    local tmpdir=""
+    tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+    local audiofile="${tmpdir}/audiofile.m4a"
 
-    exec mpv \
-        --no-terminal \
-        --no-video \
-        --ao pcm:waveheader:file=/dev/stdout \
-        "$infile"
-}
+    encode_audio "$infile" "$audiofile"
+    remux_file "$infile" "$audiofile" "$outfile"
 
-function slow_audio {
-    exec sox \
-        --temp "$tmpdir" \
-        - \
-        -t wav - \
-        speed "${SLOWDOWN}" \
-        gain -n \
-        channels 2
+    rm -rf "$tmpdir"
 }
 
 function encode_audio {
-    outfile="$1"
-    exec lame \
-        --preset standard \
-        - \
-        "${outfile}"
+    ffmpeg \
+        -i "$1" \
+        -vn \
+        "${SLOWFILTER[@]}" \
+        -c:a libfdk_aac -vbr 3 \
+        "$2"
 }
 
-function convert_file {
-    infile="$1"
-    outfile="$2"
-    tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
-    audiofile="${tmpdir}/audio.mp3"
-
-    extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
-    mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
-
-    rm -rf "$tmpdir"
+function remux_file {
+    local infile="$1"
+    local audiofile="$2"
+    local outfile="$3"
+
+    local audiodelay=""
+    audiodelay="$(get_minimum_timestamp "$infile" "audio")"
+
+    local videodelay=""
+    videodelay="$(get_minimum_timestamp "$infile" "video")"
+
+    local videotrackid=""
+    videotrackid="$(get_track_id "$infile" "video")"
+
+    local suboptions=()
+    local subtitletrackid=""
+    while read -r subtitletrackid; do
+        suboptions+=("--sync" "${subtitletrackid}:0,${OLDFPS}/${NEWFPS}")
+    done < <(get_track_id "$infile" "subtitles")
+
+    mkvmerge \
+        -o "${outfile}" \
+        --default-duration "${videotrackid}:${NEWFPS}fps" \
+        --sync "${videotrackid}:$((videodelay / 1000000))" \
+        --chapter-sync "0,${OLDFPS}/${NEWFPS}" \
+        "${suboptions[@]}" \
+        --no-audio "$infile" \
+        --sync "0:$((audiodelay / 1000000))" \
+        "$audiofile"
 }
 
+function get_track_id {
+    mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .id"
+}
 
-destdir="$1"
-shift
-
-for infile in "$@"; do
-    outfile="$destdir/$(basename "$infile")"
-
-    if [ -f "$outfile" ]; then
-        echo "Not overwriting $outfile"
-        continue
-    fi
-
-    convert_file "$infile" "$outfile"
-done
+function get_minimum_timestamp {
+    mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
+}
 
+main "$@"