Can a live streaming be performed in any condition, and what are limitations ?
Faced to some bad connectivity circumstances (Poor 3G or 4G networks), broadcast between countries or continents with limited peering (eg: between Europe and China), we considered this challenge to broadcast for Wild Touch Expedition from Antarctica to Europe with great interest.
If it’s now easy to perform a live streaming from a smartphone or a mobile transcoder attached to a camera or mixer, main issue is network quality, as usual for OTT (IP broadcast over non managed network). What could be worse that an Internet connection from Dumont d’Urville station in Adélie land ? Not much except areas not covered by any cellular network:
- Shooting scenes that require hardware which can resist to very low temperatures (such as Streambox transcoder and signal extender), even it is now Spring in Antarctica;
- Unavoidable latency due to satellite contribution (especially as geosynchronous satellites can not reach poles) and potential satellite link failures;
- Need for a low latency to be able to chat during live streaming
- Need to support peak traffic as session would be streamed on partners platforms (Arte, Nikon, BNP Paribas, Bibliothèque Nationale de France, CNRS) but also on Al Gore’s 24 Hours Of Reality (which was later cancelled due to Paris attacks).
About iReplay’s scope: if we kept adaptive bitrate streaming (ABR) as this offers the best reach on all devices (PC, mobile, tablet, TV), we chose a lower “keyframe period” than usual to get both acceptable video quality and latency (due to transcoder/decoder buffers, and necessary segmentation). To reduce latency, a PC/Mac video player with lower latency than standard. Many tests have been performed before actual live streaming, to make sure that prerequisites are satisfied, adapt every transcoder parameter (3 transoders were used. 1 in Antarctica – Streambox – , 1 transcoding satellite feed towards our adaptive streaming server delivering streams for viewers). Despite difficult conditions latency was about 4 seconds on iReplay equipments, making an end-to-end delay of about 11 seconds which is about half of what is seen on most IPTV broadcasts (eg “Direct: décalage, latence et délai en video et TV numérique, idées fausses et explications” for a French IPTV example).
To meet traffic expectations a 2 level architecture has been set up: direct distribution from transcoder/streaming server to avoid latency (CDN will add latency by caching content from origin server before delivering to viewers) for as many users as possible, and Peer to Peer to support connections that can not be supported by origin server during peak hours. As for CDN, P2P is adding latency to playback as players are trying to find other viewers which already downloaded segments, segments which have to be downloaded from other users or streaming server.
As usual for latency, it’s not a real problem for interaction, as interaction has to be done using communication standards (phone, voice over IP/Skype) rather than streaming ones. But even so, latency is still visible on an event in Antarctica.
You can watch live streaming in same conditions as it happened last Friday as recording is coming from streaming server (and not from source) here: http://www.wild-touch.org/liveantarctica-un-duplex-exceptionnel-en-direct-de-lantarctique/. Eventually, experiment was satisfying on the streaming side, even if signal failed for a few minutes on source side during event.
If you want to know more about the expedition, please connect to official website, where you can find many photos and videos. An iMAX movie, exhibition in Lyon and some photo books will be available in 2016.
If you like Luc Jacquet works (famous for his March of The Penguins movie), you can also watch “La Glace et Le Ciel” movie.