Liquidsoap – Gstreamer MPEGTS stream how to

This is a working example using Liquidsoap and it’s Gstreamer output capabilities. You are probably here because there is little to no information on how to configure this other than ambiguous examples with no explanation. I will try to attempt to explain some of the specific configuration options and my experience. First some of the requirements. This article is based on Liquidsoap v1.3.3 and Gstreamer v1.12. You will need several of the plugin packages required for the Gstreamer configuration. I recommend ffmpeg for testing purposes, Gstreamer client commands for testing are beyond painful. This example will require a computer with a CPU with AVX and/or AVX2 extensions. If the CPU does not have these extensions, it is most likely not powerful enough to do the x264 real time encoding. If this is the case you will need to stick with Liquidsoaps built in theora/vorbis video stream at about maximum of 512×376 video dimensions. At the time of this writing, I am not aware of GPU assisted encoding in Gstreamer. You may also need to sacrifice up to four Beef & Bean burritos, unfortunately there is no vegan option at the time of this writing.


#Setup Log Output And Levels For Testing. Once done testing, set to false and 3.
set("log.stdout",true)
set("log.level",10)

#Set Video Frame Width, Height, and Frame Rate. Liquidsoap will resize and if necessary add borders to the videos that are larger or smaller than these dimensions.
#Larger dimensions will increase CPU usage.
#Important: ALL VIDEOS IN SOURCE PLAYLIST MUST BE THE SAME FRAME RATE. If not you will be guaranteed desynchronized audio.
set("frame.video.width",720)
set("frame.video.height",576)
set("frame.video.samplerate",25)
set("gstreamer.add_borders", true)

#Playlist of your video files you want to stream.
#Again I reiterate: ALL VIDEOS IN SOURCE PLAYLIST MUST BE THE SAME FRAME RATE. You are going to be doing a lot of re-encoding.
source = playlist("/home/user/Videos/")

#The output pipeline you've been dreaming for. You can put the knife down now.
#
#video_pipeline: x264enc is the encoder. The default bitrate is 2048kbits, this setting is in kbits. Higher dimensions will require higher bitrate settings.
# tune=zerolatency is required for this setup. We're in the real time baby!
# pass=qual quantizer=20 are Constant Quality encoding and Quality quantizer. Consult a witch doctor for these settings.
# video/x-h264 defines our video stream mime type. profile=baseline is required. Any other profile you are on your own!
#audio_pipeline: fdkaacenc is the encoder. Other examples show the voaacenc. This is old, use the recommended fdkaacenc instead.
# bitrate setting for fdkaacenc is in bytes.
#pipeline: mpegtsmux is the MPEGTS container used for the video/audio stream.
# tcpserversink is the final destination output. The default for host=/port= are localhost:4953 so are not set in this example.
# recover-policy=keyframe sync-method=latest-keyframe These two settings are required. They set proper keyframes for connecting clients,
# otherwise the clients will never sync up as they will never receive a keyframe.
output.gstreamer.audio_video(
video_pipeline="videoconvert ! x264enc pass=qual quantizer=20 tune=zerolatency ! video/x-h264,profile=baseline ! queue ! muxer.",
audio_pipeline="audioconvert ! fdkaacenc bitrate=128000 ! queue ! muxer.",
pipeline="mpegtsmux name=muxer ! tcpserversink recover-policy=keyframe sync-method=latest-keyframe",
mksafe(source))

First you will want to check your LIQ file for errors and then fire up Liquidsoap, if it didn’t end immediately then that is a good sign. The most likely culprit will be not having one of the Gstreamer plugins, which can be easily installed by your package manager.


$ liquidsoap --check why.liq
$

(This is good, anything else your fumble fingers fucked something up)


2018/05/01 17:06:47 [output(dot)gstreamer:5] GStreamer pipeline: appsrc name="video_src" block=true caps="video/x-raw,format=RGBA,width=720,height=576,framerate=25/1,pixel-aspect-ratio=1/1" format=time blocksize=1658880 ! videoconvert ! x264enc pass=qual quantizer=20 tune=zerolatency ! video/x-h264,profile=baseline ! queue ! muxer. appsrc name="audio_src" block=true caps="audio/x-raw,format=S16LE,layout=interleaved,channels=2,rate=44100" format=time ! audioconvert ! fdkaacenc bitrate=128000 ! queue ! muxer. mpegtsmux name=muxer ! tcpserversink recover-policy=keyframe sync-method=latest-keyframe

Look for this output. Any errors in the Gstreamer configuration will occur at this point and exit Liquidsoap. If everything is good and Liquidsoap is happy it will be streaming to the localhost on port 4953. Now let’s see the video stream!


$ ffplay tcp://localhost:4953
Input #0, mpegts, from 'tcp://localhost:4953':0KB sq= 0B f=0/0
Duration: N/A, start: 3614.480000, bitrate: N/A
Program 1
Stream #0:0[0x41]: Video: h264 (Constrained Baseline) (HDMV / 0x564D4448), yuv420p(tv, bt470bg/smpte170m/bt709, progressive), 720x576 [SAR 1:1 DAR 5:4], 25 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0x42](en): Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 138 kb/s
3623.20 A-V: -0.030 fd= 3 aq= 22KB vq= 7KB sq= 0B f=0/0

ffplay is part of the ffmpeg package and makes it really easy to test the stream. There should be NO errors. If ffplay is reporting errors the most likely issue is you’ve made changes to the x264enc settings. There is a small margin of error to the conformity of the x264enc settings. The mpegtsmux only supports a handful of video and audio codecs, so be sure to check on what it supports before throwing random encoders at it. It is not recommended that this be used for end clients but as an intermediate type of output. For example, you can use ffmpeg to connect to the stream, transcode and push to an Icecast server.


ffmpeg -re -i tcp://localhost:4953 -f webm -content_type video/webm -c:v libvpx -b:v 1500K -flags:v +global_header -cpu-used 0 -qmin 10 -qmax 42 -deadline realtime -quality realtime -c:a libvorbis -flags:a +global_header icecast://source:yourpassword@localhost:8000/test.webm

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