FFmpeg piping

We can use FFmpeg to redirect / pipe input not supported by packager to packager, for example, input from webcam devices, or rtp input. The concept depicted here can be applied to other FFmpeg supported device or protocols.

Piping data to packager

There are two options to pipe data to packager.

• UDP socket

  FFmpeg supports writing to a UDP socket and packager supports reading from UDP sockets:

  $ packager 'input=udp://127.0.0.1:40000,...' ...
  $ ffmpeg ... -f mpegts udp://127.0.0.1:40000
  

  VP9 cannot be carried in mpegts. Another container, e.g. webm needs to be used when outputs VP9. In this case, transcoding has to be started after starting packager as the initialization segment is only transmitted in the beginning of WebM output.

• pipe

  Similarily, pipe is also supported in both FFmpeg and packager:

  $ mkfifo pipe1
  $ packager 'input=pipe1,...' ... --io_block_size 65536
  $ ffmpeg ... -f mpegts pipe: > pipe1
  

Note

Option -io_block_size 65536 tells packager to use an io_block_size of 65K for threaded io file. This is necessary when using pipe as reading from pipe blocks until the specified number of bytes, which is specified in io_block_size for threaded io file, thus the value of io_block_size cannot be too large.

Encoding / capture command

Camera capture

Refer to FFmpeg Capture/Webcam on how to use FFmpeg to capture webmcam inputs.

The example assumes Mac OS X 10.7 (Lion) or later. It captures from the default audio / video devices on the machine:

$ ffmpeg -f avfoundation -i "default" -f mpegts udp://127.0.0.1:40000

The command starts only after packager starts.

Note

After encoding starts, monitor encoding speed carefully. It should always be 1x and above. If not, adjust the encoding parameters to recude it.

RTP input

Assume there is an RTP input described by saved_sdp_file:

$ ffmpeg -protocol_whitelist "file,rtp,udp" -i saved_sdp_file -vcodec h264 \
  -tune zerolatency -f mpegts udp://127.0.0.1:40000

Note

For testing, you can generate an RTP input from a static media file:

$ ffmpeg -re -stream_loop 100 -i <static.mp4> -vcodec copy -an \
  -f rtp rtp://239.255.0.1:1234 -sdp_file saved_sdp_file

The command starts only after packager starts.

Note

After encoding starts, monitor encoding speed carefully. It should always be 1x and above. If not, adjust the encoding parameters to recude it.

Example packaging command in DASH

$ packager \
  'in=udp://127.0.0.1:40000,stream=audio,init_segment=live_cam_audio.mp4,segment_template=live_cam_audio_$Number$.m4s' \
  'in=udp://127.0.0.1:40000,stream=video,init_segment=live_cam_video.mp4,segment_template=live_cam_video_$Number$.m4s' \
  --mpd_output live_cam.mpd