video-to-frames

#!/bin/bash

INFO="
Convert a video to individual frames and a WAV file.

Usage:
    video-to-frames [ ... options ... ] <video> <dir>
    video-to-frames [ ... options ... ] <video> <dir> <skip>
    video-to-frames [ ... options ... ] <video> <dir> <skip> <count>

Options:
    --delay-audio <seconds>
"

DELAY_AUDIO=0
if [ "x$1" == x--delay-audio ]; then
    shift
    DELAY_AUDIO="$1"
    shift
fi

if [ "x$1" = x -o ! -f "$1" -o "x$2" = x ]; then
    echo "$INFO" 1>&2
    exit 1
fi

TMPDIR=$(mktemp -d) || exit 1
trap "rm -rf $TMPDIR" EXIT

VIDFILE="$1"
OUTDIR="$2"
FRAME_SKIP=0
[ "x$3" = x ] || FRAME_SKIP="$3"
FRAME_COUNT=0
[ "x$4" = x ] || FRAME_COUNT="$4"
mkdir -p "$OUTDIR" || exit 1

EXISTING_FRAMES=0
CLIP_NR=1
CLIP_DIR="$OUTDIR/"$(printf "video%03d" $CLIP_NR)
while [ -e "$CLIP_DIR" ]; do
    N=$(ls "$CLIP_DIR" | grep "png$" | wc -l) || exit 1
    let EXISTING_FRAMES=$EXISTING_FRAMES+$N
    let CLIP_NR=$CLIP_NR+1
    CLIP_DIR="$OUTDIR/"$(printf "video%03d" $CLIP_NR)
done
mkdir "$CLIP_DIR" || exit 1

if [ "x$EXISTING_FRAMES" != x0 ]; then
    echo "Info: Detected $EXISTING_FRAMES video frames in '$OUTDIR'" 1>&2
fi

FPS=$(ffprobe "$VIDFILE" -v 0 -select_streams v \
    -print_format flat -show_entries stream=r_frame_rate) || exit 1
FPS=$(echo "$FPS" | cut -d '"' -f 2) || exit 1
FPS=$(bc <<<"scale=8; $FPS") || exit 1

echo "Info: Detected frame rate: $FPS fps" 1>&2

if [ "x$FRAME_COUNT" = x0 ]; then
    echo "Extracting frames (skip=$FRAME_SKIP)..."
    ffmpeg -loglevel 16 -accurate_seek -r 1 -i "$VIDFILE" \
        -an -ss "$FRAME_SKIP" \
        -f image2 "$CLIP_DIR/f%08d.png" || exit 1
else
    echo "Extracting $FRAME_COUNT frames (skip=$FRAME_SKIP)..."
    ffmpeg -loglevel 16 -accurate_seek -r 1 -i "$VIDFILE" \
        -an -ss "$FRAME_SKIP" -t "$FRAME_COUNT" \
        -f image2 "$CLIP_DIR/f%08d.png" || exit 1
    N_CREATED=$(ls "$CLIP_DIR" | wc -l)
    if [ "x$N_CREATED" != "x$FRAME_COUNT" ]; then
        echo "Error: extracted $N_CREATED frames out of $FRAME_COUNT!" 1>&2
        exit 1
    fi
fi

AUDIO_SKIP=$(bc <<<"scale=8; ($FRAME_SKIP)/($FPS) - ($DELAY_AUDIO)") || exit 1
AUDIO_PAD=$(bc <<<"scale=8; ($EXISTING_FRAMES)/($FPS)") || exit 1

case "$AUDIO_SKIP" in
    -*)
        AUDIO_PAD=$(bc <<<"scale=8; ($AUDIO_PAD)-($AUDIO_SKIP)") || exit 1
        AUDIO_SKIP=0
    ;;
esac

AUDIO_FILE="$OUTDIR/"$(printf "audio%03d.wav" $CLIP_NR)

if [ "x$AUDIO_PAD" = x0 ]; then
    echo "Importing audio (skip=${AUDIO_SKIP}s)..."
    ffmpeg -loglevel 16 -i "$VIDFILE" -ss "$AUDIO_SKIP" -vn \
        "$AUDIO_FILE" || exit 1
else
    echo "Importing audio (skip=${AUDIO_SKIP}s, pad=${AUDIO_PAD}s)..."
    ffmpeg -loglevel 16 -i "$VIDFILE" -ss "$AUDIO_SKIP" -vn \
        "$TMPDIR/audio_2.wav" || exit 1
    A_CHAN=$(sox --i -c "$TMPDIR/audio_2.wav") || exit 1
    A_RATE=$(sox --i -r "$TMPDIR/audio_2.wav") || exit 1
    sox -r "$A_RATE" -c "$A_CHAN" -n "$TMPDIR/audio_1.wav" \
        trim 0 "$AUDIO_PAD" || exit 1
    sox "$TMPDIR/audio_1.wav" "$TMPDIR/audio_2.wav" \
        "$AUDIO_FILE" || exit 1
fi

exit 0