Sayonara Silverlight: How Panopto Switched to Flash and HTML5
Panopto is a lecture and presentation capture and sharing platform used by leading academic institutions and Fortune 500 companies around the world. The company recently transitioned the platform from Silverlight to a new technology stack that streams HTTP Live Streaming (HLS) end-to-end. Former chief product officer and now CEO Eric Burns (right) oversaw the transition, and answered our questions about where technologies like DASH, MSE, and Flash fit it.
Why the switch from Silverlight?
Three things drove our shift away from Silverlight. First, the Microsoft video stack, which for a time was a technically superior online streaming solution, began to give way to HTML5 video adoption and Flash support for H.264/AAC. Second, Microsoft’s announcement of Silverlight end-of-life created the perception that Silverlight and Smooth Streaming were legacy technology. Finally, Google’s announcement of NPAPI deprecation accelerated the market end-of-road for Silverlight.
What is the architecture now?
The default experience is Flash with HTML5 fallback in cases where Flash isn’t installed. This approach allows us to target the same browser support matrix as we had with the Silverlight implementation, and the use of Flash allows us to continue supporting adaptive streaming.
Technically, HLS is our base format for desktop and iOS delivery. We also have a JavaScript layer in our desktop player that decodes the HLS into chunks that Flash can play. We send a single stream to Android since HLS support is spotty.
HTML5 (H.264/AAC) is an option in all of our playback experiences. This includes our interactive video player, in which we serve two synchronized streams of HTML5 video. It also includes our single-stream embeddable player and our mobile apps for iOS and Android.
Why Flash First?
We knew we had to change platforms, and when we started down the HTML5/DASH path, we were excited about working with emerging W3C standards. Unfortunately, we quickly found a number of implementation gotchas and inconsistent support across browsers and platforms. So we took a step back and asked, “What technology will keep us in business?” We choose the one with the least technological risk.
How has the transition gone? Have their been gotchas on computers or iOS and Android devices?
The transition has been remarkably smooth. We expected to hit encoder and decoder inconsistencies that would require multiple encodings for different output devices. What we found, however, is that H.264 decoder compatibility has become quite mature. As a result, if you’re using the 3.1 Main, and if you’re reasonably conservative with your encoding settings, you’re able to target most video-capable devices with a single ABR group encoding.
That, in turn, requires less compute and storage to get from capture to playback, and enables us to encode video on the client and instantly publish to the server.
Why not use Media Source Extensions (MSE)? When will that be ready?
The first step in our transition away from Silverlight was to reach 100 percent browser matrix compatibility and ensure that any HTML5-only browser could serve a high-quality Panopto viewing experience. With MSE not supported in Firefox and older versions of IE, it wasn’t critical to support it in our first non-Silverlight release. Looking ahead, we want to replicate the current Flash experience in HTML5, and we expect MSE to be a part of that.
Why not use Dynamic Adaptive Streaming over HTTP (DASH)?
We see DASH as the future. It’s a truly open standard that isn’t controlled by any single entity. That said, the protocol still has a long way to go in terms of standardization and consistent browser support. By contrast, HLS is a mature protocol whose adoption has grown far beyond the iOS ecosystem.
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