X-Git-Url: https://code.delx.au/transcoding/blobdiff_plain/698521ee62495859c3dab544eac316a308d983c1..19b49083e7946fe60a37912ed449a41da7c1ba70:/fix-pal-speedup

diff --git a/fix-pal-speedup b/fix-pal-speedup
index 39c4ba4..17e5e01 100755
--- a/fix-pal-speedup
+++ b/fix-pal-speedup
@@ -3,78 +3,63 @@
 # 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.
+# slowed, and encoded as AAC, preserving surround sound.
 
 if [ -z "$1" -o -z "$2" ]; then
-    echo "Usage: $0 destdir infile [infile ...]"
+    echo "Usage: $0 infile outfile"
     exit 1
 fi
 
 set -xe
 FORCEFPS="24"
-SLOWDOWN="0.96"
+SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
 
 function mux_replace_audio {
-    infile="$1"
-    audiofile="$2"
-    outfile="$3"
-
-    trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
-    mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
+    local infile="$1"
+    local audiofile="$2"
+    local outfile="$3"
+
+    local audiodelay="$(get_audio_delay "$infile")"
+    local videotrackid="$(get_video_trackid "$infile")"
+
+    mkvmerge \
+        -o "${outfile}" \
+        --default-duration "${videotrackid}:${FORCEFPS}fps" \
+        --no-audio "$infile" \
+        --sync "0:$((audiodelay / 1000000))" \
+        "$audiofile"
 }
 
-function extract_audio {
-    infile="$1"
-
-    exec mpv \
-        --no-terminal \
-        --no-video \
-        --ao pcm:waveheader:file=/dev/stdout \
-        "$infile"
+function get_video_trackid {
+    mkvmerge -i "$1" | sed -n 's/Track ID \([0-9]*\): .*video.*/\1/p'
 }
 
-function slow_audio {
-    exec sox \
-        --temp "$tmpdir" \
-        - \
-        -t wav - \
-        speed "${SLOWDOWN}" \
-        gain -n \
-        channels 2
+function get_audio_delay {
+    mkvmerge -F json -i "$1" | \
+        jq -r '.tracks[] | select(.type == "audio") | .properties.minimum_timestamp'
 }
 
 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"
+    local infile="$1"
+    local outfile="$2"
+    local audiofile="${tmpdir}/audiofile.m4a"
 
-    extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
-    mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
-
-    rm -rf "$tmpdir"
+    encode_audio "$infile" "$audiofile"
+    mux_replace_audio "$infile" "$audiofile" "$outfile"
 }
 
 
-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
-
+infile="$1"
+outfile="$2"
+tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+convert_file "$infile" "$outfile"
+rm -rf "$tmpdir"