LiveSim2

As the original simulator (livesim1), the output is a wall-clock (UTC) synchronized infinite linear stream of segments. This achieved by looping input VoD DASH assets, and changing time stamps so that an infinite “live” stream is available. The synchronization is done modulo asset duration, for example: a 1-hour asset restarts every hour on full hours, and a 30s asset restarts every 30s on full and half minutes. If there is a clock display in the video, and the length is full minutes or similar, it is therefore easy to directly see how long the system delay is from publishing to screen presentation. The very short example assets bundled with the code are only 8s long, which means that they restart every time the UTC time is a multiple of 8s, relative to the Epoch start 1970-01-01:00:00:00Z.

To provide full UTC time stamps on-screen and the possibility to test subtitles, livesim2 has a new feature for generating subtitles for any number of languages. This is done by a URL parameter like /timesubsstpp_en,sv which will result in two stpp (segmented TTML) subtitle tracks with with language codes “en” and “sv”, respectively. There is a corresponding setting for wvtt (segmented WebVTT) subtitles using /timesubswvtt_en,sv.

The new livesim2 software is written in Go instead of Python and designed to handle content in a more flexible and versatile way. It is intended to be very easy to install and deploy locally since it is compiled into a single binary that serves the content via a built-in performant HTTP/2 server. There is also a very simple way of setting up HTTPS using Let´s Encrypt.

Similarly to livesim1, the output is highly configurable by adding parameters inside the URLs. These parameters are included not only in the MPD requests, but in all segment requests allowing the server to be stateless, and be able to generate streams with a huge number of parameter variations. Currently, not all parameters of livesim1 are implemented, but there are also new parameters like the generated subtitles mentioned above.