12/20/2023 0 Comments Ffmpeg encode h265…įfmpeg wiki asserts that this is typical for hardware accelerated encoding: It does this by taking motion into account. It will compress different frames by different amounts, thus varying the QP as necessary to maintain a certain level of perceived quality. This typically leads to a hugely varying bitrate over the entire sequence.Ĭonstant Rate Factor is a little more sophisticated than that. … The quantization parameter defines how much information to discard from a given block of pixels (a Macroblock). Werner Robitza explaining why CRF still allows to save bits in comparison to setting constant QP: It worth noting that this is still different from CRF because constant quality, as it is determined by -cq, sets constant quantization parameter (CQP) instead. You probably want to consider that to help in your case. Dennis Mungai's detailed answer to ' How can I use CRF encoding with nvenc in ffmpeg?' at Superuser suggests to use -cq:v 19 and -rc:v vbr parameters instead to get constant quality with variable bitrate. with ffmpeg -h encoder=hevc_nvenc -hide_banner. You can check what the encoder supports, e.g. The hardware accelerated encoders do not support Constant Rate Factor (CRF, -crf) to determine size/quality ratio.
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