Difference between " -g " and "-keyint" parameter? usage syntax?

[pxstein]

As far as I know there are two possible ffmpeg parameters for specifiying the maximum keyframe interval:

-g 50

and

-keyint 50

Whats the difference?

Furthermore I have seen various parameter syntax usages for keyint:

-keyint 50

-keyint=50

-preset slow -x264-params keyint=50

Whats the difference?

[Selur]

libavcodec provides some generic global options, which can be set on all the encoders and decoders. In addition each codec may support so-called private options, which are specific for a given codec.

source: https://www.ffmpeg.org/ffmpeg-all.html#Codec-Options
So if you use an encoder which has it's own parameters use those to be sure the encoder does what you want.
Otherwise you can use '-g' which is a generic option which should set the gop size (<> key frame intervall) for all encoders that support it.

I have never seen '-keyint xy' or '-keyint=xy' as a global option, assuming those really exists they are probably only used for a specific encoder.

-x264-params keyint=50

is an example of the encoder specific option of the x264 encoder to set the gop size.


So directly to your questions:

-g 50

and

-keyint 50

Whats the difference?

that the second option does not exist in that way afaik.

Furthermore I have seen various parameter syntax usages for keyint:

-keyint 50

-keyint=50

-preset slow -x264-params keyint=50

Whats the difference?

That only the last variant exists as far as I know.

[jagabo]

In case it's not clear...

-g N is ffmpeg's own GOP size argument. ffmpeg translates that and passes it along to individual encoders in whatever format is appropriate for that encoder. -x264-parmams is ffmpeg's argument to pass options directly to the x264 encoder. What follows it is passed specifically to x264. It's usually used for settings that ffmpeg doesn't support directly. But you can also use it for settings that ffmpeg supports. If you use both -g X and -x264-params keyint=Y the latter will be used for the encoding.