fish: functions/tsd: Add a helper to analyse GStreamer timestamps

fish/.config/fish/functions/tsd.fish

@@ -0,0 +1,23 @@
+# This function is to help us analyse timestamp difference given a file with
+# a single column where each row has GStreamer PTS/DTS/Duration or timestamp
+# of the form HH:MM:SS:sssssssss in each row.
+# Adapted from https://stackoverflow.com/questions/8903239/how-to-calculate-time-elapsed-in-bash-script
+function tsd --description "Get timestamp difference between rows" -a file
+    if test (count $argv) -lt 1
+        echo "Usage: tsd <file_name>"
+        echo "Eg: tsd gstreamer-ts.log"
+    else
+        set -l RESULT_FILE /tmp/gst-ts-analysis.csv
+
+        if test -e $RESULT_FILE
+            echo "Result file $RESULT_FILE exists, removing..."
+            rm $RESULT_FILE
+        end
+        while read -la first_line; and read -la second_line
+            set -l fist_date $(date -u -d "$first_line" +"%s.%N")
+            set -l second_date $(date -u -d "$second_line" +"%s.%N")
+            date -u -d "0 $second_date sec - $fist_date sec" +"%H:%M:%S.%N" >>$RESULT_FILE
+        end <$file
+        nvim -R $RESULT_FILE
+    end
+end