FFmpeg Live stream

February 23, 2018

YouTube Live streaming (optionally including other sites simultaneously) with screensharing is simple and stable with FFmpeg or OBS Studio.

Webcam:

ffmpeg \
-f alsa -ac 2 -i hw:1,0 \
-f v4l2 -r 10 -i /dev/video0 \
-c:v libx264 -pix_fmt yuv420p -preset ultrafast -g 20 -b:v 2500k \
-c:a aac -ar 44100 \
-threads 0 -bufsize 512k \
-f flv rtmp://a.rtmp.youtube.com/live2/YOURSTREAM &> stream.log

FFmpeg audio option -f alsa -ac 2 -i hw:1,0 uses -ac 2 for stereo to hardware address 1,0. For default audio device, use -f alsa -i pulse. Obtain hardware addresses via arecord -l. Note that monoaural -ac 1 doesn’t work on some hardware. -c:a aac -ar 44100 is AAC encode audio at 44.1 kHz sampling frequency (passing audio up to about 22 kHz, CD-quality).

FFmpeg video option -f v4l2 -r 10 -i /dev/video0 say to acquire video from webcam /dev/video0 at 10 fps, using the native resolution of the webcam. Force webcam resolution like -s 640x480. -c:v libx264 -pix_fmt yuv420p -preset ultrafast -g 20 -b:v 2500k encodes video using the H.264 video compression algorithm, prioritizing reduced CPU utilization, in blocks of 20 frames with a target bitrate of 2.5 Mbps.

FFmpeg config -threads 0 -bufsize 512k lets FFmpeg choose the number of CPU threads, with a 512kB buffer. Adjust buffer size as needed–tradeoff between latency and robustness. -f flv rtmp://a.rtmp.youtube.com/live2/YOURSTREAM &> stream.log uses the FLV container format, live stream to YouTube, with stream ID YOURSTREAM. Don’t let others know the Stream ID!.

Screenshare: use the same command as above, swapping -f v4l2 -r 10 -i /dev/video0 with

-f x11grab -r 10 -s 1024x720 -i :0.0+0,24

-f x11grab -r 10 -s 1024x720 -i :0.0+0,24 sets screengrab at 10 fps, starting in the upper left hand corner, send a 1024x720 pixel video. If your screen resolution is more than 1024x720, there would be unsent regions at the bottom and/or right side.

Audio-only:

ffmpeg -f alsa -ac 2 -i pulse -c:a aac -ar 8000 -f rtp rtp://localhost:1234

Connect from the local or remote PC to rtp:://serverip:1234.