add a script to convert mkv to mpeg4

convert-mkv-to-mp4.sh

@@ -0,0 +1,112 @@
+#!/bin/bash
+#
+# convert-mkv-to-mp4.sh
+#
+# Copyright (c) 2014 Don Melton
+#
+
+about() {
+    cat <<EOF
+$program 1.0 of July 9, 2014
+Copyright (c) 2013-2014 Don Melton
+EOF
+    exit 0
+}
+
+usage() {
+    cat <<EOF
+Convert Matroska video file into MP4 format without transcoding.
+
+Usage: $program [OPTION]... [FILE]
+
+    --help      display this help and exit
+    --version   output version information and exit
+
+Requires \`ffprobe\`, \`ffmpeg\` and \`mp4track\` executables in \$PATH.
+Output is written to current working directory.
+EOF
+    exit 0
+}
+
+syntax_error() {
+    echo "$program: $1" >&2
+    echo "Try \`$program --help\` for more information." >&2
+    exit 1
+}
+
+die() {
+    echo "$program: $1" >&2
+    exit ${2:-1}
+}
+
+readonly program="$(basename "$0")"
+
+case $1 in
+    --help)
+        usage
+        ;;
+    --version)
+        about
+        ;;
+esac
+
+readonly input="$1"
+
+if [ ! "$input" ]; then
+    syntax_error 'too few arguments'
+fi
+
+if [ ! -f "$input" ]; then
+    die "input file not found: $input"
+fi
+
+readonly output="$(basename "$input" | sed 's/\.[^.]*$//').mp4"
+
+if [ -e "$output" ]; then
+    die "output file already exists: $output"
+fi
+
+for tool in ffprobe ffmpeg mp4track; do
+
+    if ! $(which $tool >/dev/null); then
+        die "executable not in \$PATH: $tool"
+    fi
+done
+
+readonly container="$(ffprobe -show_format "$input" 2>/dev/null | sed -n '/^format_name=/p' | sed 's/^.*=//;s/,.*$//')"
+
+if [ "$container" != 'matroska' ]; then
+    die "input file not Matroska format: $input"
+fi
+
+readonly track1="$(ffprobe -show_streams -select_streams a:0 "$input" 2>/dev/null | sed -n '/^codec_name=/p' | sed 's/^.*=//;s/,.*$//')"
+readonly track2="$(ffprobe -show_streams -select_streams a:1 "$input" 2>/dev/null | sed -n '/^codec_name=/p' | sed 's/^.*=//;s/,.*$//')"
+
+adjust_defaults=''
+
+if [ "$track1" == 'ac3' ] && [ "$track2" == 'aac' ]; then
+    map_options='-map 0:2 -map 0:1'
+    adjust_defaults='true'
+
+elif [ "$track1" == 'aac' ]; then
+    map_options='-map 0:1'
+else
+    die "input file does not contain compatible audio tracks: $input"
+fi
+
+echo "Converting: $input" >&2
+
+time {
+    ffmpeg \
+        -i "$input" \
+        -map 0:0 \
+        $map_options \
+        -c copy \
+        "$output" \
+        || exit 1
+
+    if [ "$adjust_defaults" ]; then
+        mp4track --track-index 1 --enabled true "$output" &&
+        mp4track --track-index 2 --enabled false "$output" || exit 1
+    fi
+}