This method allows the encoder to attempt to achieve a certain output quality for the whole file when output file size is of less importance. This is the recommended rate control mode for most uses. Use this rate control mode if you want to keep the best quality and care less about the file size.

To know more about what the different rate control modes do see this post. This will determine the file size and also how quality is distributed. Rate control decides how many bits will be used for each frame. There are two rate control modes that are usually suggested for general use: Constant Rate Factor (CRF) or Two-Pass ABR. See HWAccelIntro for information on supported hardware H.264 encoders. If you need help compiling and installing see one of our compiling guides. It assumes you have ffmpeg compiled with -enable-libx264. Is there some warning or output that notes that the bitrate was insufficient to reach the target quality that I'm not seeing? That would at least allow me to brute force this.This guide focuses on the encoder x264. But if I have to set the bitrate correctly for every cq value, what is the point of the cq value? I would just set cq=1 and test various bitrates, which would then only be applicable to a specific video. If I do set a maxrate, it is observed by the encoder.

The resultant video has an overall bitrate of ~100Mb/s. I'm seeing the encoder use as many bits as possible, not as many bits as needed. If maxBitRate is not specified, the encoder will use as many bits as needed to achieve the target quality.īut that's not the behavior I'm observing. If I don't specify a maxrate, the documentation indicates: Per documentation, I can also specify a maxBitRate (maxrate=). (Using cq=1, cq=20, and cq=51 all output a file with the same hash.) HOWEVER, that only outputs the same perfect quality video of extremely large size for any cq value. This should be enough to test various values of cq. I specify a Variable Bit Rate rate control mode (rc=vbr_hq) and a target quality (cq=). To use the h264_nvenc encoder through ffmpeg and with a target quality, I follow the instructions in Nvidia's documentation, last paragraph of the linked anchor. I seek to ascertain the end-product quality of various cq ('constant quality') values for the h264_nvenc video encoder.

H264_nvenc quality