One of the files I downloaded was Light Speed, and it’s shown in Bitrate Viewer below. Essentially, Vimeo is telling FFmpeg to encode to a CRF value of 20 with a max rate of 5500 and a VBV buffer of 15000 (see here for more on VBV buffer).

To produce capped CRF, you specify a CRF value and a maximum rate and buffer size, which are also highlighted in the MediaInfo screen above. Of course, you can’t use CRF-only encodes for streaming since limiting the data rate is key to deliverability. CBR and VBR encodes do the reverse, and adjust quality to meet the specified data rate. See here for a complete explanation of capped CRF including FFmpeg command strings. When you encode with CRF and no cap, FFmpeg prioritizes quality over bitrate and varies the bitrate to deliver the specified quality, which ranges from 1-51 with lower numbers delivering higher quality. But here’s what I’m thinking and why.īy way of background, most producers use capped CRF as a DIY per-title encoding technique. No disrespect intended for Vimeo, who has a fabulous team of encoding professionals. This doesn’t mean that Vimeo isn’t using AV1, it could be that my download tool simply doesn’t capture the AV1 encode.īut, I did notice that Vimeo was using CRF 20, which IMHO, is suboptimal and prompted the resurrection of this article. Periodically, I download a file to see if this is so so far, no AV1 encodes.

Why was I trolling Vimeo? Because they promised a few months ago, with great fanfare, that they were encoding their staff picks using the AV1 codec. This morning, however, I downloaded a video from Vimeo and noticed they were encoding with capped CRF with a CRF value of 20, which you can see in MediaInfo below. I hadn’t written this article yet because I figured it was too obscure for most readers. Most of the analysis shown below was for this client (who approved my discussion in an article). Late last year, I consulted with a large OTT shop that used capped CRF encoding with a CRF value of 19 for the top files in the encoding ladder. If you are using capped CRF encoding (for constant rate factor), however, you almost certainly will find it interesting and perhaps even illuminating.Ī quick background note. If you’re not using capped CRF encoding, or considering the same, it’s almost certainly not of interest. In a blog full of wonky compression articles, this could be the wonkiest article of all.

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