NAL_HRD relationship to VBV

[Gregleto]

Hi all,

Our Telestream x264 GUI requires NAL_HRD to be enabled and set to VBR in order for us to set VBV. With NAL_HRD set to "Disabled", the option to set VBV numbers is disabled. Can anyone explain the relationship between VBV and NAL_HRD? More importantly, is there a dependency that requires NAL_HRD to be enabled in order to set VBV levels? It doesn't make sense to me so I feel I must be misunderstanding something.

Thanks,

Gregleto

[Blue_MiSfit]

Well, I'm not the expert, but as far as I understand the HRD information is there to inform the decoder what vbv parameters were chosen by the encoder.

It's certainly possible to encode a stream using VBV without signaling NAL HRD or VCL HRD, but this may not work with all decoders. I think this is why Telestream inherently links the two options. I actually think this is a good idea, but again I'm not the expert.