Add discompress

.local/bin/discompress

@@ -0,0 +1,82 @@
+#!/bin/bash
+#
+# Re-encode a video to a target size in MB.
+# Example:
+#    ./this_script.sh video.mp4 15
+
+T_SIZE="$2" # target size in MB
+T_FILE="${1%.*}-$2MB.mp4" # filename out
+
+# Original duration in seconds
+O_DUR=$(\
+    ffprobe \
+    -v error \
+    -show_entries format=duration \
+    -of csv=p=0 "$1")
+
+# Original audio rate
+O_ARATE=$(\
+    ffprobe \
+    -v error \
+    -select_streams a:0 \
+    -show_entries stream=bit_rate \
+    -of csv=p=0 "$1")
+
+# Original audio rate in KiB/s
+O_ARATE=$(\
+    awk \
+    -v arate="$O_ARATE" \
+    'BEGIN { printf "%.0f", (arate / 1024) }')
+
+# Target size is required to be less than the size of the original audio stream
+T_MINSIZE=$(\
+    awk \
+    -v arate="$O_ARATE" \
+    -v duration="$O_DUR" \
+    'BEGIN { printf "%.2f", ( (arate * duration) / 8192 ) }')
+
+# Equals 1 if target size is ok, 0 otherwise
+IS_MINSIZE=$(\
+    awk \
+    -v size="$T_SIZE" \
+    -v minsize="$T_MINSIZE" \
+    'BEGIN { print (minsize < size) }')
+
+# Give useful information if size is too small
+if [[ $IS_MINSIZE -eq 0 ]]; then
+    printf "%s\n" "Target size ${T_SIZE}MB is too small!" >&2
+    printf "%s %s\n" "Try values larger than" "${T_MINSIZE}MB" >&2
+    exit 1
+fi
+
+# Set target audio bitrate
+T_ARATE=$O_ARATE
+
+
+# Calculate target video rate - MB -> KiB/s
+T_VRATE=$(\
+    awk \
+    -v size="$T_SIZE" \
+    -v duration="$O_DUR" \
+    -v audio_rate="$O_ARATE" \
+    'BEGIN { print  ( ( size * 8192.0 ) / ( 1.048576 * duration ) - audio_rate) }')
+
+# Perform the conversion
+ffmpeg \
+    -y \
+    -i "$1" \
+    -c:v libx264 \
+    -b:v "$T_VRATE"k \
+    -pass 1 \
+    -an \
+    -f mp4 \
+    /dev/null \
+&& \
+ffmpeg \
+    -i "$1" \
+    -c:v libx264 \
+    -b:v "$T_VRATE"k \
+    -pass 2 \
+    -c:a aac \
+    -b:a "$T_ARATE"k \
+    $T_FILE