Videogen

[Glendora Starr]

Helloeveryone! Today I wanted to talk about testing live streams. As you will probably have guessed: in order to truly test a live stream you'll need to be able to give it a live input. In some cases that might be a bit of a challenge, especially if you only have shell access and no live input available. It's for those situations that we've got a script that uses ffmpeg to generate a live feed which we call videogen. The script itself is made for Linux servers, but you could take the ffmpeg command line and use it for any server able to run ffmpeg.

Videogen is a simple generated live stream for testing live input/playback without the need for an actual live source somewhere. It is built on some of the examples available at the ffmpeg wiki site. It looks like this:

As you might've suspected, in order to use videogen you'll need ffmpeg. Make sure to have it installed or have the binaries available in order to run videogen. By now ffmpeg is so popular almost every Linux distro will have an official package for it.

As an alternative to ffmpeg you can also use our Gstreamer script to generate a live test feed. In practise it's nearly the same as videogen, though because we made this one slightly harder to encode it's easier to get higher bitrates with.

Videogen is rather easy to use, but it does require some manual input as you need to specify the output, but you can specify any of the codecs inside as well incase you want/need to use something else than our default settings.

As it's all run locally it doesn't really matter which protocol you'll be using except for one point. RTMP cannot handle multi bitrate using this method, so if you want to create a multi bitrate videogen you'll usually want to use TS.

You'll have access to any of the additional parameters that ffmpeg provides for both video and audio encoding simply by just adding them after the videogen command. Ffmpeg handles the last given parameters if they overwrite previously given parameters. For all the ffmpeg parameters we recommend checking the ffmpeg documentation for codecs, video and audio.

This changes the resolution. The default of videogen is 800x600, so setting this to 1920x1080 will make it a "HD" stream, though the quality is barely noticeable with this script. We tend to use screen resolutions to verify a track is working correctly.

This changes the video codec. The default is h264 baseline profile of 3.0, which should be compatible with any modern device. Changing the codec to H265 (HEVC) or "default" h264 changes things and might be exactly what you want to find out. Do note that HEVC cannot work over RTMP, use RTSP or TS instead!

This changes the audio codec. The default is aac, so knowing how to set mp3 instead can be handy. Just be sure to add an audio rate as MP3 tends to bug out when it's not set. We tend to use 44100 as most devices will work with this audio rate.

Obviously you would want to try out a multi bitrate videogen as well, which you can do but will want to use TS for instead of RTMP as RTMP cannot handle multi bitrate through a single stream as push input.

You can put the streams on always on to have a continuous live stream or leave them on default settings and only start the live stream when you need it. Keep in mind that as long as they're active they will use CPU.

Gstreamer can provide a live stream as well and it helps having another method than just ffmpeg. There is no big benefit to Gstreamer vs ffmpeg for this use-case, so we would recommend to go with what you're familiar with.

The usage is like videogen, but if you want to do something else than RTMP you will need to make quite some edits to the pipeline. We will keep things simple for this one and stay on RTMP. Let us know if you're interested in a deeper dive for Gstreamer and we will update the article or create a new one.

We've created a megamix which you can use to verify both track switching and retention of track information with. You can also loop this into MistServer instead of running a script. Keep in mind that any time you use a VOD stream browsers tend to keep that in cache, so when it loops you might be looking at the cache instead of what comes out of your server.

On request we have added several high resolution streams for our users to help check out their server limits. Consider using most of these files only on local networks as they would fail over most internet connections.

This is a 1min 50sec video of 148mbps. This is meant to test how your system deals with high bitrate streams. Keep in mind that the bitrate of this video is actually higher than most internet connections would be able to handle, so expect playback to fail.Qualities come in:

This is a 2min 20sec video of 62mbps. This stream is also meant to test how your system deals with high bitrate streams, only in a slightly more normal resolution format. Expect playback to fail for most connections.

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