I am not sure which command solve it but, it solved with the following ffmpeg command;

$ffmpegCmd = "ffmpeg -y -i " . escapeshellarg($inputPath) . " " .
            "-vf \"format=yuv420p,scale=1080:1920:force_original_aspect_ratio=decrease," .
            "pad=1080:1920:(ow-iw)/2:(oh-ih)/2,setsar=1\" " .
            "-c:v libx264 -preset medium -profile:v baseline -level 3.0 " .
            "-color_range tv -colorspace bt709 " .
            "-pix_fmt yuv420p " .
            "-r 30 -g 60 -keyint_min 60 -sc_threshold 0 -x264opts no-scenecut " .
            "-c:a aac -b:a 128k -ac 2 -ar 48000 " .
            "-movflags +faststart " .
            "-video_track_timescale 15360 " .
            "-max_muxing_queue_size 9999 " .
            escapeshellarg($outputPath);