From 13b29ee757f14bfad0429d21b02135e3c27f7dba Mon Sep 17 00:00:00 2001
From: Clifton Palmer <clifton.james.palmer@protonmail.com>
Date: Fri, 30 May 2025 13:25:10 +0300
Subject: [PATCH] Calculate a/v ratio on the fly

---
 add-audio-to-video.sh | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/add-audio-to-video.sh b/add-audio-to-video.sh
index e03bfda..3f35043 100755
--- a/add-audio-to-video.sh
+++ b/add-audio-to-video.sh
@@ -11,12 +11,27 @@ then
 fi
 
 tmp_video=tmp$$.mp4
-ratio=0.65
+
+function get_duration() {
+	ffmpeg -i $1 2>&1 | \
+		awk -F, '/Duration/{print $1}' | \
+		awk -F: '{print $2*3600 + $3*60 + $4}'
+}
+
+duration_audio=`get_duration $input_audio`
+echo Duration of audio is $duration_audio seconds
+
+duration_video=`get_duration $input_video`
+echo Duration of video is $duration_video seconds
+
+av_ratio=$(echo "2k $duration_audio $duration_video / p" | dc)
+echo Calculated audio/video ratio is $av_ratio
+
 
 # make video about the same length as the audio
 ffmpeg \
 	-i $input_video \
-	-filter:v "setpts=${ratio}*PTS" \
+	-filter:v "setpts=${av_ratio}*PTS" \
 	$tmp_video
 
 # adds audio to video,
@@ -31,5 +46,4 @@ ffmpeg \
 	-b:a 192k \
 	output.mp4
 
-
 [[ -f $tmp_video ]] && rm $tmp_video
-- 
2.47.2