Others simulate this with a very constrained ‘variable bit rate’ mode either way, use the -b option to set the bit rate. Some codecs have a true ‘constant bit rate’ mode, where a certain number of bits are allocated to a second of the video/audio. If quality is of secondary concern to control of file size, you can target a bit rate. Unless you absolutely need the output file to be a certain size, you should generally take this approach. There are some encoders (like x264 and libfdk_aac) that use their own special option for determining quality. For example, using -c:v mpeg4 -q:v 3 will encode MPEG4 video at a very high quality. Normally, this is set with the -qscale (‘quality scale’), or -q option, with a numerical scale determined by the specific encoder (but generally between 1-31). You can target a certain ‘quality level’, letting the encoder decide what bit rate should be used to achieve that quality. For now, you can just endure the work-in-progress state: I’ve done my best to ascertain that all of this information is accurate (I’ve tested much of it myself), so no need to worry on that front. This document is a draft form I may change things around & will probably split the video & audio sections into two separate articles at some time in the future. For archiving audio I would generally recommend FLAC, but see this hydrogenaudio comparison and decide for yourself. I am in the process of writing a guide for intermediate video codecs. This guide concentrates on some common delivery codecs, and it is not an exhaustive list.

Ffmpeg video codecs