Dolby Vision output using CPQ mode

[hyllm]

Is there any reason why this is not supported???

[rigaya]

dolby vision has bitrate limits and CQP mode cannot set bitrate limits even if you want.

Actually there might be no need to limit, but I'll keep it as-is.

[quamt]

Hi @rigaya, thanks for the explanation.

Just to confirm a few things so I understand the scope correctly:

1. Is this CQP/Dolby Vision limitation specific to NVEncC only, or does the same constraint apply to your other encoders (QSVEncC and VCEEncC) as well?

2. What encode modes do you recommend for Dolby Vision output?

3. Does this restriction apply to all Dolby Vision profiles, or only to profiles with strict bitrate requirements?

In particular, is this mainly a concern for dual-layer DV (BL+EL), or also for single-layer DV where RPU/metadata is embedded in the HEVC stream?

Thank you.

[rigaya]

I did not put much thought into this particular limitation, I simply thought using --qvbr or --vbr shall be enough.

But there seems to be some time you want to use --cqp, so I have removed limitation in NVEnc 9.08 so you can try using CQP.

[hyllm]

thanks!!!

[quamt]

Hi @rigaya,

Because I’m trying not just to “light up the DV logo” but also stay reasonably close to Dolby’s own specifications, I did a bit more reading in the official docs. Rapid summary of what I think matters for the encoder side:

• The Dolby Vision Profiles and Levels spec defines, for each level, the maximum frame rate, resolution and maximum combined bit rate for base + enhancement layer. It doesn’t mandate any particular rate-control algorithm, just that the resulting bitstream sits within those constraints and follows the standard HRD/DPB rules for the underlying codec (HEVC Main 10, etc.).
  Example public copy of the spec:
  https://www.scribd.com/document/370572697/Dolby-Vision-Profiles-Levels

• For UHD Blu-ray (Profile 7), the Dolby Vision UHD Blu-ray Authoring Workflow Guide talks about system bit-rate limits and recommended BL/EL bit-rate ratios, again in terms of resulting bit rates rather than specific CBR/VBR/CQP modes.
  https://professional.dolby.com/siteassets/pdfs/dolby_vision_uhd_bluray_authoring_workflow.pdf

From that, my takeaway is: Dolby doesn’t care whether the encoder uses CBR, VBR, QVBR, CQP, ICQ, etc. It only cares that the final stream respects the profile/level bit-rate caps and buffer constraints. The rate-control mode needs to be “safe enough” to stay under those limits.

With that in mind, can I sanity-check the following with you and ask for a tiny docs note?

1. NVEncC (HEVC 10-bit + DV)
   Now that CQP is unblocked in 9.08, is it fair to say that all HEVC 10-bit RC modes that NVENC exposes (CQP, CBR, VBR, VBRHQ, QVBR, etc.) are technically usable with --dolby-vision-rpu, but that for strict DV profile/level compliance you’d still recommend VBV-limited modes (CBR/VBR/QVBR with --max-bitrate/--vbv-bufsize) and treat CQP more as an “expert / use at your own risk if you know the peaks stay under the level” option?

2. QSVEncC
   QSVEnc historically blocked DV + CQP (resulting in the “Please use Bitrate Mode - CBR / VBR / AVBR / VCM / Quality VBR” error), but newer versions removed the DV-specific mode restriction. From your perspective, is the idea now basically the same as NVEncC, i.e., that any HEVC 10-bit mode the Intel SDK supports can be combined with --dolby-vision-rpu, but that rate-control modes with a defined VBV/bit-rate target are the sensible recommendation for DV work?

3. VCEEncC
   For HEVC 10-bit + --dolby-vision-rpu in VCEEncC, are there any extra limitations from AMF or your implementation (e.g. “don’t use CQP with DV on certain GPUs”), or should we assume the same rule of thumb: all modes technically work, but VBV-limited ones are preferred if you care about staying inside Dolby’s level bit-rate caps?

If this matches your intent, a short note in the options docs for each encoder, like:

Dolby Vision: Any HEVC 10-bit rate-control mode supported by the hardware can be used with --dolby-vision-rpu. For better Dolby Vision profile/level compliance, prefer CBR/VBR/QVBR (with appropriate max-bitrate/VBV settings). CQP/ICQ modes do not inherently respect level bit-rate limits, so they are recommended only for advanced users who understand the trade-offs.

…would be super helpful.

Thanks again for your hard work and for clarifying this.