====== ffmpeg - Video - Duration ======

===== Using Regex =====

<code bash>
# Use perl-regex.
ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | tail -n 1 | grep -Po "(?<=time=)([0-9]{1,2}:[0-9]{2}:[0-9]{2})"

or

# Use extended-regex.
ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | tail -n 1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}"

or

ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}" | tail -n 1

or

ffmpeg -i "input.mkv" 2>&1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}" | head -n 1
</code>

<WRAP info>
**NOTE:**  This gets the figures directly from ffmpeg.

  * This returns an estimate of the duration based on the bitrate and size of the file.

</WRAP>

----

===== Getting the data from the video stream =====

<code bash>
ffprobe -v error -select_streams v:0 -show_entries stream=duration -of default=noprint_wrappers=1:nokey=1 "input.mkv"
</code>

<WRAP info>
**NOTE:**  This often returns N/A for .mkv files.
</WRAP>

----

===== Getting the data from the container =====

<code bash>
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "input.mkv"

ffprobe -v error -select_streams v:0 -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "input.mkv"
</code>

<WRAP important>
**WARNING:**  This returns the duration of the entire container, and not just the duration of the video.
</WRAP>

----

===== By Packet duration_time =====

This method reads each video packet, individually, and totals up each packet size.

  * Sums up the **duration_time** of the **-show_entries** command.

<code bash>
video_pkt_durations=$(ffprobe -v error -select_streams v:0 -skip_frame nokey -show_entries packet=duration_time -of default=nokey=1:noprint_wrappers=1 "input.mkv")

sum_video_pkt_duration=0
precision=6
count_video_pkt_duration=0

#echo "Calculating video pkt_duration..."
for video_pkt_duration in $video_pkt_durations; do
  sum_video_pkt_duration=$(echo "${sum_video_pkt_duration} + ${video_pkt_duration}" | bc)

  (( count_video_pkt_duration++ ))
done;

video_duration=$( echo "scale=${precision}; ${sum_video_pkt_duration} " | bc)

echo "DURATION=${video_duration}"
echo "VIDEO FRAMES=${count_video_pkt_duration}"
</code>

<WRAP info>
**NOTE:**  This is very accurate but may take a while.
</WRAP>

----

===== Calculate duration using Size and Bitrate =====

<code bash>
duration=$( echo "scale=6; (${video_size} * 8) / ${bitrate}" | bc)
</code>

----

===== Calculate duration using Size and Bitrate =====

<code bash>
duration = NUMBER_OF_FRAMES / FPS
</code>

<WRAP info>
**NOTE:**  Returns the duration in seconds.
</WRAP>

----