[FFmpeg-user] ffmpeg -g option

[Moritz Barsnick]

Hi Parag,
why are you top-posting?

> As explained in the link (http://en.wikipedia.org/wiki/Group_of_pictures)
>  that we  can specify the GOP structure by two variables M , N . But what
> it seems from the -g option is that we can only specify the N (distance
> between the two I frames) not M . So can we have other option to specify
> completely the GOP structure in ffmpeg ?

I found the documentation for "-g", it's in this section:

https://www.ffmpeg.org/ffmpeg-all.html#Codec-Options

N is specified by the "-bf" option:

 ‘bf integer (encoding,video)’

    Set max number of B frames between non-B-frames.

    Must be an integer between -1 and 16. 0 means that B-frames are
    disabled. If a value of -1 is used, it will choose an automatic value
    depending on the encoder.

    Default value is 0.

I'm not sure this default value is valid for all codecs though. I would
have thought libx264 defaults to using B-frames. libx264 also has much
finer options to control the type of frames it produces.

Parag, why do you ask? Just out of curiosity, or are you trying to
achieve something special?

Moritz