95 lines
3.0 KiB
ReStructuredText
95 lines
3.0 KiB
ReStructuredText
FFmpeg piping
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=============
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We can use *FFmpeg* to redirect / pipe input not supported by *packager*
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to *packager*, for example, input from webcam devices, or rtp input. The concept
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depicted here can be applied to other *FFmpeg* supported device or protocols.
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Piping data to packager
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-----------------------
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There are two options to pipe data to packager.
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- UDP socket
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*FFmpeg* supports writing to a UDP socket and *packager* supports reading
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from UDP sockets::
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$ packager 'input=udp://127.0.0.1:40000,...' ...
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$ ffmpeg ... -f mpegts udp://127.0.0.1:40000
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VP9 cannot be carried in mpegts. Another container, e.g. webm needs to be
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used when outputs VP9. In this case, transcoding has to be started after
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starting packager as the initialization segment is only transmitted in the
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beginning of WebM output.
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- pipe
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Similarily, pipe is also supported in both *FFmpeg* and *packager*::
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$ mkfifo pipe1
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$ packager 'input=pipe1,...' ... --io_block_size 65536
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$ ffmpeg ... -f mpegts pipe: > pipe1
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.. note::
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Option -io_block_size 65536 tells packager to use an io_block_size of 65K
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for threaded io file. This is necessary when using pipe as reading from pipe
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blocks until the specified number of bytes, which is specified in
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io_block_size for threaded io file, thus the value of io_block_size cannot
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be too large.
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Encoding / capture command
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--------------------------
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Camera capture
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^^^^^^^^^^^^^^
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Refer to `FFmpeg Capture/Webcam <https://trac.ffmpeg.org/wiki/Capture/Webcam>`_
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on how to use *FFmpeg* to capture webmcam inputs.
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The example assumes Mac OS X 10.7 (Lion) or later. It captures from the default
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audio / video devices on the machine::
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$ ffmpeg -f avfoundation -i "default" -f mpegts udp://127.0.0.1:40000
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The command starts only after packager starts.
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.. note::
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After encoding starts, monitor encoding speed carefully. It should always be
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1x and above. If not, adjust the encoding parameters to recude it.
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RTP input
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^^^^^^^^^
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Assume there is an RTP input described by `saved_sdp_file`::
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$ ffmpeg -protocol_whitelist "file,rtp,udp" -i saved_sdp_file -vcodec h264 \
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-tune zerolatency -f mpegts udp://127.0.0.1:40000
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.. note::
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For testing, you can generate an RTP input from a static media file::
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$ ffmpeg -re -stream_loop 100 -i <static.mp4> -vcodec copy -an \
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-f rtp rtp://239.255.0.1:1234 -sdp_file saved_sdp_file
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The command starts only after packager starts.
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.. note::
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After encoding starts, monitor encoding speed carefully. It should always be
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1x and above. If not, adjust the encoding parameters to recude it.
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Example packaging command in DASH
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---------------------------------
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::
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$ packager \
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'in=udp://127.0.0.1:40000,stream=audio,init_segment=live_cam_audio.mp4,segment_template=live_cam_audio_$Number$.m4s' \
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'in=udp://127.0.0.1:40000,stream=video,init_segment=live_cam_video.mp4,segment_template=live_cam_video_$Number$.m4s' \
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--mpd_output live_cam.mpd
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