Capturing and streaming with ffmpeg while displaying locally

Question

I can capture with ffmpeg from a device, I can transcode the audio/video, I can stream it to ffserver.

How can I capture and stream with ffmpeg while showing locally what is captured?

Up to now I've been using VLC to capture and stream to localhost, then ffmpeg to get that stream, transcode it again, and stream to ffserver.

I would like to do this using ffmpeg only.

Answer 1

Option A: Use ffmpeg with multiple outputs and a separate player:

• output 1: copy source without transcoding and pipe it or send it to a local port

• output 2: transcode and send to server

  Example using ffplay

  ffmpeg -f x11grab [grab parameters] -i :0.0 \
  [transcode parameters] -f [transcode output] \
  -f rawvideo - | ffplay -f rawvideo [grab parameters] -i -
  

Option B: ffmpegonly with OpenGL and a SDL window (requires SDL and --enable-opengl)

    ffmpeg -f x11grab [grab parameters] -i :0.0 \
    [transcode parameters] -f [transcode output] \
    -f opengl "Window title"

Answer 2

You can also use tee separately what is more error prone for me (I couldn't get aergistal's solution to work):

cat file | tee >(program_1) [...] >(program_n) | destination

In this case:

ffmpeg -i rtsp://url -codec:a aac -b:a 192k -codec:v copy -f mpegts - | \
       tee >(ffplay -f mpegts -i -) | \
       ffmpeg -y -f mpegts -i - -c copy /path/to/file.mp4

(Tested with ffmpeg v:3.2.11 [current in Debian stable])