When milliseconds matter: Real-time multilingual subtitling at global sports broadcast scale

Live sport coverage at this scale is among the most technically demanding broadcast environments in the world. Commentary moves fast, terminology is highly specialised, and the production infrastructure spans multiple feeds, platforms, and regulatory jurisdictions simultaneously.

The broadcaster's existing captioning workflow had reached its limits. Subtitle latency was exceeding acceptable thresholds for viewer experience and broadcast compliance in key markets. Delivering accurate multilingual subtitles at pace across concurrent streams, without rebuilding the existing playout infrastructure, required a fundamentally different approach.

The broadcaster had evaluated and ruled out generic AI captioning tools. Accuracy on domain-specific commentary, including technical race terminology and the full roster of driver and team names, was simply too poor to meet broadcast standards.

CaptionHub deployed Timbra, its real-time subtitling engine, in partnership with Norsk, the developer platform for rapidly building high-availability live media workflows. CaptionHub had already been building its real-time captioning capabilities on Norsk's infrastructure when the broadcaster opportunity emerged—and Norsk's ability to rapidly extend its platform to enable timing metadata for the project meant the solution could be delivered at a pace that a more traditional integration would never have allowed. Norsk handles SRT ingest from the broadcaster's existing feed, passing it directly into Timbra and allowing the solution to slot into the existing playout workflow without requiring any infrastructure changes.

Timbra's ASR models were fine-tuned on sports commentary, with a custom terminology dictionary covering event-specific vocabulary. The result: high-accuracy transcription at speeds that generic models could not match. Translated subtitles were automatically routed to four language outputs and delivered as WebVTT via the broadcaster's existing CDN and playout infrastructure.

The solution is fully automated. Using the CaptionHub API, the broadcaster's own systems start and stop captioning, manage output, and control the full workflow—with no manual intervention required. Captioning runs as a silent, invisible layer within their existing infrastructure: configured once, triggered automatically, entirely within their control. For a team operating at the pace of live sport, that operational simplicity is as valuable as the technology itself.