Why Transcoding Matters
Not every video file plays everywhere. An MKV with a DTS audio track might work fine on your desktop but fail completely on a browser or Apple TV. Different devices support different codecs, containers, and bitrates.
Transcoding solves this by converting your original file into a universally compatible format. In Lumen, that means remuxing into an MP4 container with AAC audio — the most widely supported combination across all modern devices.
The Lumen Pipeline
When you upload a file to Lumen, here is what happens:
- Upload to cloud storage — your file goes directly to Cloudflare R2 via a secure presigned URL
- Transcoding kicks in — our transcoding workers detect the new file and begin processing
- Smart remuxing — if your video is already H.264, we remux rather than re-encode, preserving quality while saving time
- Audio normalization — audio tracks are converted to AAC for universal compatibility
- Subtitle extraction — embedded subtitle tracks are extracted via ffprobe and converted to WebVTT
- Stream delivery — the final MP4 with faststart metadata is uploaded back to R2, ready for instant playback
Why Not HLS?
Many streaming platforms use HLS (HTTP Live Streaming) which splits video into small segments. While HLS offers adaptive bitrate streaming, it adds complexity and storage overhead. For personal libraries where you control the source quality, a single well-optimized MP4 with faststart provides excellent performance with simpler infrastructure.
We may add adaptive bitrate streaming in the future for users with very large libraries or variable connection speeds.
Speed and Efficiency
Because we remux when possible rather than fully re-encoding, most files are ready to stream within minutes of uploading. A typical 1080p movie takes just a few minutes to process. Full re-encoding is only triggered when the source codec is not web-compatible.
Zero Effort for You
The entire pipeline runs automatically. Upload your file, confirm the metadata match, and by the time you grab a snack, your movie is ready to play on any device. No settings to configure, no codecs to research, no command-line tools to install.
That is what cloud transcoding should feel like.