How do I use ffmpeg to pause a stream?

Tech QnA
1

I want to pause the stream for a while, but I’m not sure how. Is there a specific command to do this? If so, could you kindly let me know?

2

Yes, to pause a stream using FFmpeg, you can use the “setpts” filter to slow down the stream to a halt.

To put it another way, you can adjust the presentation timestamps of video frames using the FFmpeg “setpts” filter. You can alter the presentation timestamps to speed up or slow down the video playback in an efficient manner. You can set the presentation timestamps to make it look as though the video has stopped when you wish to create a pause effect.

For a more thorough explanation, see this:

ffmpeg -i input_stream -vf "setpts=N/FRAME_RATE/TB" -c:a copy output_stream

  • Input stream is specified using the -i option.
  • -vf “setpts=N/FRAME_RATE/TB”: The presentation timestamps are altered using the “setpts” filter.
    In this instance, N denotes the frame number, FRAME_RATE the video’s frame rate, and TB is the time base. You can alter the formula to regulate the video’s speed.

You can change the command to, for instance, pause the video for five seconds by doing the following:

ffmpeg -i input_stream -vf "setpts=5*PTS" -c:a copy output_stream

Within this altered command:

5*PTS slows down the video to a stop for the predetermined amount of time by setting the new presentation timestamp to five times the original value.
Remember that this method might add extra frames to keep the presentation slowed down, and the exact length of the pause will depend on the frame rate of the video.

It’s important to remember that although this technique produces a visual pause, it’s a simulated effect inside the video stream and might not offer actual interactive control similar to a conventional media player pause button.

Refer to this link if you face further issues regarding live streaming

3

Can you please give me an example of how to use this filter if possible?

4

Here is an example command that will pause a stream and save the output to a file:
ffmpeg -i input.mp4 -vf “setpts=1000000/1” output.mp4
This command will take the input stream “input.mp4” and apply the “setpts” filter with a value of “1000000/1”, which will effectively pause the stream by slowing it down to a halt. The output will be saved to a file named “output.mp4”.

5

This means the same filter will be used to speed up the stream, am I right?

6

Absolutely yes, you can also use the “setpts” filter to slow down or speed up a stream by setting the value to a fraction different from “1/1”. For example, to play the stream at half speed, you can use the following command:
ffmpeg -i input.mp4 -vf “setpts=1/2” output.mp4I hope this helps! Let me know if you have any questions.