Streaming using twitch.tv

Twitch.tv is one of the more popular RTMP based streaming services offered. As Steam has a Linux client available, some people may be in search of solutions to stream their games or Linux desktop. The info included here should serve as a list of such solutions.

Twitch streaming Guidelines

From Twitch.tv support:

Video Requirements

• Codec: H.264 (x264)
• Mode: Strict CBR
• Keyframe Interval: 2 seconds

Audio Requirements

• Codec: AAC-LC or MP3, Stereo or Mono
• Maximum bit rate: 160 kbps (AAC), 128 kbps (MP3)
• Sampling frequency: any (AAC), 44.1 KHz (MP3)

Other Requirements

Not listed on their page is a requirement of the Y'UV420p pixel format, as Y'UV444 is not widely supported just yet.

GUI solutions

• Open Broadcaster Software (obs-studio) is a popularly used streaming program that is now available in the community repo. Alpha Linux builds (obs-studio-git^AUR from the AUR) are also available for compiling & testing.
• Castawesome (castawesome^AUR from the AUR) is a Gtk3 frontend for ffmpeg streaming with builtin Twitch.tv support.
• SimpleScreenRecorder (lib32-simplescreenrecorder from the official repositories) can be configured to stream to twitch.
  • For this to work:
    • The container needs to be set to FLV
    • RTMP URL needs to be put in the 'save as' field
    • make sure 'separeate file per segment' is unchecked
    • video codec set to libx264 (NOT H.264)
    • set bitrate to reasonable value, such as 2000 kbps
    • in the custom option field, enter preset=fast,minrate=2000,maxrate=2000,bufsize=2000,keyint=60
    • Note: The value of 'minrate', 'maxrate' and 'bufsize' should be equal to the bit rate

Ffmpeg solutions

These solutions revolve around making use of the FFmpeg package:

.bashrc script method

One method of streaming to twitch using FFMPEG makes use of a simple script that is placed in a user's ~/.bashrc file. this script supports streaming of both desktop and OpenGL elements.

• Depending on your internet upload speed, you may need to modify the Ffmpeg parameters. use the breakdown list for reference.

The script can be used by typing

streaming streamkeyhere

into a terminal. While it is running, use pavucontrol to edit sound sources. The .bashrc script is as follows:

 streaming() {
     INRES="1920x1080" # input resolution
     OUTRES="1920x1080" # output resolution
     FPS="15" # target FPS
     GOP="30" # i-frame interval, should be double of FPS, 
     GOPMIN="15" # min i-frame interval, should be equal to fps, 
     THREADS="2" # max 6
     CBR="1000k" # constant bitrate (should be between 1000k - 3000k)
     QUALITY="ultrafast"  # one of the many FFMPEG preset
     AUDIO_RATE="44100"
     STREAM_KEY="$1" # use the terminal command Streaming streamkeyhere to stream your video to twitch or justin
     SERVER="live-fra" # twitch server in frankfurt, see http://bashtech.net/twitch/ingest.php for list
     
     ffmpeg -f x11grab -s "$INRES" -r "$FPS" -i :0.0 -f alsa -i pulse -f flv -ac 2 -ar $AUDIO_RATE \
       -vcodec libx264 -g $GOP -keyint_min $GOPMIN -b:v $CBR -minrate $CBR -maxrate $CBR -pix_fmt yuv420p\
       -s $OUTRES -preset $QUALITY -tune film -acodec libmp3lame -threads $THREADS -strict normal \
       -bufsize $CBR "rtmp://$SERVER.twitch.tv/app/$STREAM_KEY"
 }

Ffmpeg Parameter breakdown

Parameter	Description
ffmpeg	The converter
-f x11grab	-f forces input to be from x11grab
-s $INRES	-s sets a specific image size, relying on the variable $INRES
-r $FPS	-r sets framerate to be the value equal to $FPS
-i :0.0	-i gets input, in this case its pulling in screen :0.0 from x11. Can be adjusted, e.g. -i :0.0+500,100 to start at screenpos 500/100
-b:v $CBR	-b:v specifies that the video bitrate is to be changed. the value of the bitrate is set by $CBR
-ab 96k	-ab sets audio bitrate to 96k. -b:a is the alternate form of this command
-f alsa	forces input(?) to be from alsa
-ac 2	sets audio channels to 2
-i pulse	gets input from pulse
-vcodec libx264	sets video codec to libx264
-crf 23	sets the ffmpeg constant rate factor to 23
-preset "$QUAL"	sets the preset compression quality and speed
-s "1280x720"	specifies size of image to be 720p
-acodec libmp3lame	sets audio codec to use libmp3lame
-ar 44100	sets audio rate to 44100 hz
-threads 0	sets cpu threads to start, 0 autostarts threads based on cpu cores
-pix_fmt yuv420p	sets pixel format to Y'UV420p. Otherwise by default Y'UV444 is used and is incompatible with twitch
-f flv "$URL"	forces format to flv, and outputs to the twitch RTMP url