bash: displaying filtered & dynamic output of ffmpeg - bash

Question

After this question whose the answer had partially resolved my problem.
I would like to have a selected result of ffmpeg.
So, with this command:
ffmpeg -y -i "${M3U2}" -vcodec copy -acodec copy "${Directory}/${PROG}_${ID}.mkv" 2>&1 | egrep -e '^[[:blank:]]*(Duration|Output|frame)'
The result is:
Duration: 00:12:28.52, start: 0.100667, bitrate: 0 kb/s
Output #0, matroska, to '/home/path/file.mkv':
But in the result I am missing this dynamic line:
frame= 1834 fps=166 q=-1.0 Lsize= 7120kB time=00:01:13.36 bitrate= 795.0kbits/s
This line changes every second. How can I modify the command line to display this line? My program should read this line and display the "time" updating in-place. Thanks
solution:
ffmpeg -y -i "${M3U2}" -vcodec copy -acodec copy "${Directory}/${PROG}_${ID}.mkv" 2>&1 |
{ while read line
do
if $(echo "$line" | grep -q "Duration"); then
echo "$line"
fi
if $(echo "$line" | grep -q "Output"); then
echo "$line"
fi
if $(echo "$line" | grep -q "Stream #0:1 -> #0:1"); then
break
fi
done;
while read -d $'\x0D' line
do
if $(echo "$line" | grep -q "time="); then
echo -en "\r$line"
fi
done; }
Thanks to ofrommel

Answer 1

You need to parse the output with CR (carriage return) as a delimiter, because this is what ffmpeg uses for printing on the same line. First use another loop with the regular separator to iterate over the first lines to get "Duration" and "Output":
ffmpeg -y -i inputfile -vcodec copy -acodec copy outputfile 2>&1 |
{ while read line
do
if $(echo "$line" | grep -q "Duration"); then
echo "$line"
fi
if $(echo "$line" | grep -q "Output"); then
echo "$line"
fi
if $(echo "$line" | grep -q "Stream mapping"); then
break
fi
done;
while read -d $'\x0D' line
do
if $(echo "$line" | grep -q "time="); then
echo "$line" | awk '{ printf "%s\r", $8 }'
fi
done; }