[FFmpeg-user] Controlling an ffmpeg stream?

Roy Pardi lists at roypardi.com
Thu Sep 8 00:00:27 EEST 2016

Hi, I am new to the list and also to ffmpeg so this is likely to be a naive question.

My question concerns the command line version of ffmpeg. I am developing a cross-platform app in Adobe AIR and the problem I am trying to solve is being able to seek to an arbitrary point in a video file without having to render the video with a keyframe every frame. I am able to launch ffmpeg in the background and pipe a stream of an existing video file to my client app. Here are my questions:

1. Am I wrong in my understanding that ffmpeg will seek to a requested time, rendering from the nearest keyframe?

2. Using Actionscript I can successfully launch ffmpeg with:

	ffmpeg -re -i  test.mp4  -c:a copy -c:v copy -f flv - 

and subscribe to the stream and display it. I am also able to seek using:

	ffmpeg  -ss 300 -re -i  test.mp4  -c:a copy -c:v copy -f flv - 

What I am not able to do is to communicate with or control ffmpeg through stdin once it has started streaming, either to tell it to seek or to pause the stream. I can’t tell if my code is bad or if I misunderstanding the ffmpeg command line tool. Is the tool only designed for a "set up/run/exit” usage scenario.

I can provide more details if needed. 



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