Ripbot264 raspberry pi12/6/2023 Note that Netflix proposes using fixed-QP encoding for its per-shot encoding optimization to achieve optimal encodes for each scene. Good for: Video encoding research, or if you have no CRF mode 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. 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. To know more about the idea behind QP, you can read this tutorial (if you’re not afraid of some maths). Note: libvpx does not have a fixed QP mode.įfmpeg -i -c:v libx265 -x265-params qp=23 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. Large values mean that there will be higher quantization, more compression, and lower quality. The Quantization Parameter controls the amount of compression for every macroblock in a frame. Don’t worry about this-just keep in mind that there’s no point in achieving an exact target bitrate if it’s wasteful. This means that if you have a scene that is very easy to encode, your bitrate may always end up lower than the one you specified. For libvpx, ffmpeg needs to be compiled with -enable-libvpx.Ī word of caution: Encoders like x264 by default do not unnecessarily “stuff” frames with bits. With x265, not all parameters can be passed directly, so you have to use the -x265-params option. You can find more information on the options supported by the encoders in the documentation.įor x265, you may have to compile ffmpeg with -enable-libx265. I will be basing my post on the modes supported by the popular H.264 and H.265 encoders x264 and x265, as well as libvpx, as available in ffmpeg. Now, let’s dive into the different modes. Knowing the scenario helps you choose a rate control mode. You want to ensure that the file ends up having a certain size.
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