How Playback built a global stadium for watching sports together

Playback is building the future of sports TV. An experience that feels like going to watch your favorite team in a packed arena — except at internet scale. Ari Borensztein, CTO and cofounder of Playback, explains their unique vision: "We're the only platform that's fully real-time, and we're the only platform that's really built at this point for sports creators and fans."

There were numerous technical challenges the Playback team faced in realizing this vision:

• Ultra-low latency streaming of sporting events to all viewers
• Support for potentially millions of concurrent viewers for any given event
• Synchronization between all viewers
• Consistent performance and QoS across a worldwide audience
• Ability for any viewer to share commentary or react in realtime over live video

Betting on WebRTC

For Playback’s use case, synchronization was crucial. Ari explains, “For sports, if you're not experiencing the event happening on the screen at the same time or very close to the same time, it's just a fundamentally broken experience."

The team decided to use WebRTC. The protocol was designed for realtime delivery and with a small jitter buffer on the receiving end, no subscribers to a media stream accumulate more than than 200ms of drift. Ari, the CTO of Playback elaborates: "We [needed synchronized delivery to fans] and WebRTC was the obvious fit. There's really just nothing else that delivers the consistent sub-few-hundred-millisecond synchronization out of the box."

The Playback team built the initial version of their application from the ground up using a combination of a homegrown ingestion pipeline for capturing sports streams, an open source WebRTC server to fan the broadcasts out to viewers, and a commercial CPaaS to host a separate virtual commentator booth for fans to chat and react live.

"We were building our own WebRTC stack from the ground up", Ari explained. "The challenges we faced before integrating LiveKit were mainly around scale and ensuring that our implementation and infrastructure were set up to grow with us.

The challenges we faced before integrating LiveKit were mainly around scale and ensuring that our implementation and infrastructure were set up to grow with us.

LiveKit drafted first overall

After securing content rights with the NBA, Playback needed a unified system that could handle the anticipated growth and have the flexibility to build new features. The team discovered LiveKit during an evaluation of numerous commercial and open source WebRTC stacks. Key differentiators for them were:

• Scale. "Just not having to worry about our ability to scale has been massive," noted Ari. "We went from being in a position where we had to make really difficult decisions around over-provisioning and overspending to protect ourselves against usage spikes, to now being able to just have LiveKit worry about that scaling for us and have a predictable cost."
• Performance. LiveKit had consistently high FPS across various regions, including challenging markets in Latin America and Asia.
• Adaptive bitrate. Dynamic delivery of 4K, 1080p, 540p, or 360p based on ever-changing network conditions.
• Advanced codecs. VP9 ****paired with LiveKit’s pricing model kept bandwidth lower for users and reduced costs. Ari shared, "The bandwidth based price structure has been really great, and that's something that's pretty different from what we had seen with other WebRTC services.”
• Playout delay. A unique feature LiveKit supports allowing the programmatic (or automatic) adjustment of jitter buffer size, giving the ability to control quality against latency while ensuring synchronization amongst all viewers. For live sports quality is paramount to users and for Playback, having fine-grained control over this was a game-changer.

Warming up with a new stack

Instead of doing a complete rewrite of their existing system, Playback took a phased approach to moving their realtime stack over to LiveKit. "We broke the LiveKit migration into stages," Ari said. "First we moved the [sports stream ingestion] over and sunset our internal system. Then we moved on to the stage and the screen share. This was a good way for us to learn incrementally and avoid doing everything in one fell swoop."

Once the team was up and running on their LiveKit stack, they began to rapidly expand Playback’s feature set towards their vision of a collaborative platform. As Ari described, "Collaboration is a first-class feature on Playback. It's not just one streamer broadcasting to a bunch of people. It's multiple streamers, a group of friends streaming together, or even bringing the audience into the stream." As general purpose realtime network infrastructure, LiveKit was designed to support a myriad of streaming data workflows.

In a matter of months Playback shipped:

• Live “stages” for fans to commentate, commiserate and celebrate together
• Multistreaming to other platforms like Twitch or YouTube
• Recording for VOD and instant replay support (i.e. clip creation)

Ari highlights, "These are all things that had been on our roadmap, and we kind of just had to hook up the plumbing and we could get them out the door using LiveKit’s features instead of building them from the ground up." He emphasized the ease of working with LiveKit: "I found the LiveKit SDKs to be super developer-friendly and straightforward. Once you master the core concepts of the LiveKit stack, it all clicks and it's very easy to work with."

I found the LiveKit SDKs to be super developer-friendly and straightforward. Once you master the core concepts of the LiveKit stack, it all clicks and it's very easy to work with.

On deck for Playback

With a unified and scalable WebRTC foundation in place, Playback is laser focused on their mission to reimagine how fans experience live sports. As Ari puts it, "We're aimed at achieving a new level of user engagement, enhancing both our team's performance and the fan experience."

On the heels of signing new content deals and a slew of upcoming features, Ari offers this advice to fellow developers: "Don't try to reinvent the wheel. Building companies is really hard, and there's going to be no end of challenges to find product-market fit and to grow and create value. If you can work with an existing solution that meets your requirements, it'll save you a lot of time and headaches and allow you to focus on the things that really differentiate your business."