Best SVT-AV1 Bitrate Control Technique for Live Streaming

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There are four bitrate control techniques worth considering for live encoding/transcoding using the SVT-AV1 codec. These are:

• Capped CRF
• VBR
• Capped VBR
• Constrained VBR

Here’s what I found: Overall:

• Capped CRF shows promise with significant bitrate savings, good quality retention, and the best overall performance by ~10 – 25% (meaning more streams from the same hardware).
• VBR was generally the best of the three VBR variants.
• Capped VBR was very similar to VBR with no significant advantages (again, in the live use case).
• Constrained VBR produced a more consistent bitrate, but had:
  • The highest peak bitrates (potential deliverability issues).
  • The lowest average VMAF score of the three VBR variants.
  • The lowest low-frame quality scores, indicating the potential for transient quality issues.
• Bottom line: Either use VBR or capped CRF.

You can download a report detailing these findings here. No registration is required.