Blackmagic Forum

Steve Alexander wrote:You can render DNxHR in HQX or 444, or ProRes HQ (?) or I believe HEVC (H265) and select the 422 10-bit option. Perhaps others will chime-in with additional suggestions. There may be a Cineform option, for example. What is your source media?

Steve Alexander wrote:Assuming you are asking about H265, the encoding profile is Main 422 10. If you don't see this, perhaps it is a Studio-only option, I don't know. You should be able to use a 10-bit flavour of ProRes or DNx, though.

Jim Simon wrote:I use these.

HDR Deliver 2.png

Jim Simon wrote:Mine come out 4:2:0.

But for delivery, that's OK. I've found issues playing back 4:2:2 on anything other than a computer.

Plus, everything you watch is 4:2:0 - Blu-ray, Netflix, Amazon, YouTube, etc.

4:2:2 really only has a place during editing. And for that, I favor DNx or Cineform.

Andrew Kolakowski wrote:There is no 4:2:2 h265 encoder in Resolve (unless your GPU supports it, but I don't think there is any atm.).

Andrew Kolakowski wrote:For 10bit use Main10 and it's 4:2:0. There is no 4:2:2 h265 encoder in Resolve (unless your GPU supports it, but I don't think there is any atm.).
Main 10 4:4:4 as name suggests is 10bit YUV 444 based and it's available on newer GPUs.

If you want to use h265 10bit 4:2:2 then this is rather unusual case (more for own usage/archival) and better off to use DNxHR/ProRes.
If you really need it then MainConcept plugin for Resolve should have it.

Jim Simon wrote:I use these.

HDR Deliver 2.png

dn9909 wrote:Why "Constant QP" instead of the default "Variable Bitrate"?

Code: Select all

Constant QP (CQP)

The Quantization Parameter controls the amount of compression for every macroblock in a frame. Large values mean that there will be higher quantization, more compression, and lower quality. Lower values mean the opposite. QP ranges from 0 to 51 in H.264, and you can easily set a fixed QP for your entire encoding process with x264 and x265. Note: libvpx does not have a fixed QP mode.

ffmpeg -i <input> -c:v libx264 -qp 23 <output>
ffmpeg -i <input> -c:v libx265 -x265-params qp=23 <output>
To know more about the idea behind QP, you can read this tutorial (if you’re not afraid of some maths).

Unless you know what you’re doing and you explicitly want this, it is suggested not use this mode! Setting a fixed QP means that the resulting bitrate will be varying strongly depending on each scene’s complexity, and it will result in rather inefficient encodes for your input video. The quality will be good if you set a low enough QP, but in contrast to CRF (see below), you may waste space, or you have no control of the actual bitrate.

Good for: Video encoding research, or if you have no CRF mode
Bad for: Almost anything else

Note that Netflix proposes using fixed-QP encoding for its per-shot encoding optimization to achieve optimal encodes for each scene. This however requires a lot of processing and careful assembly of the individual encoded shots, so it’s not a “one size fits all” method you should use unless you have the whole framework implemented.

Andrew Kolakowski wrote:If you don't care about bitrate much, but want relatively same quality for every master then you can use QP.

Jim Simon wrote:Here's what I mean about best quality/size balance. This is a bit oversimplified, but it gives the basic idea.

When using CQ, a frame that needs 10 bits will get 10 bits. A frame that needs 30 bits will get 30 bits.

When using CBR at 20, the frame that needs 10 will still get 20, thus bloating file size. And the frame that needs 30 also gets 20, thus reducing quality.

VBR at 20 is a little better. The frame that needs 10 will get 10, so no file bloat. But the frame that needs 30 will only get 20, thus reducing quality.

CQ offers best balance with a single pass encode.

Andrew Kolakowski wrote:max will be fixed.

Constant Quality (CQ) / Constant Rate Factor (CRF)

I’ve talked about the Constant Rate Factor in another article in more detail. It basically gives you constant quality throughout your encoding process. It’s a “set and forget” thing—just specify the CRF and let the encoder do the rest.

ffmpeg -i <input> -c:v libx264 -crf 23 <output>
ffmpeg -i <input> -c:v libx265 -crf 28 <output>
ffmpeg -i <input> -c:v libvpx-vp9 -crf 30 -b:v 0 <output>
In H.264 and H.265, CRF ranges from 0 to 51 (like the QP). 23 is a good default for x264, and 28 is the default for x265. 18 (or 24 for x265) should be visually transparent; anything lower will probably just waste file size. Values of ±6 will result in about half or twice the original bitrate. For VP9, the CRF can be from 0 to 63. Recommended values are from 15–35.

The only downside with this mode is that you don’t know what the resulting file size or the fluctuation of the bitrate will be.

Note that a two-pass and CRF encode with the same resulting bitrates should be identical in quality. The main difference is that with two-pass, you can control the file size (if that is a requirement), whereas with CRF you just specify the quality you want.

Good for: Archival; achieving the best possible quality
Bad for: Streaming; obtaining a certain bitrate / file size

Jim Simon wrote:Mine come out 4:2:0.

But for delivery, that's OK. I've found issues playing back 4:2:2 on anything other than a computer.

Plus, everything you watch is 4:2:0 - Blu-ray, Netflix, Amazon, YouTube, etc.

4:2:2 really only has a place during editing. And for that, I favor DNx or Cineform.