Parameters for "framerate" and "keyframe interval"?

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Parameters for "framerate" and "keyframe interval"?

Ben Stover
For video codec H.264 there are two parameters:

Framerate (e.g. 25 or 30 or 29,97)

  and

keyframe interval (I guess measured in seconds after the last keyframe .e.g 50 or 200):

What are the corresponding cmdline parameters for ffmpeg?

How can I tell ffmpeg to use the same values as the input?

Thank you
Ben
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Re: Parameters for "framerate" and "keyframe interval"?

He Lei

"ffmpeg -r 25 -i in.file ... out.file"



usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}…
In here, [infile options] is "Video options”.

look at help of ffmpeg:(cmd is 'ffmpeg -h | more’).

/*
Video options:
-vframes number     set the number of video frames to output
-r rate             set frame rate (Hz value, fraction or abbreviation)
-s size             set frame size (WxH or abbreviation)
...
*/

LeiHe
[hidden email]<mailto:[hidden email]>



在 2018年10月26日,下午5:41,Ben <[hidden email]<mailto:[hidden email]>> 写道:

For video codec H.264 there are two parameters:

Framerate (e.g. 25 or 30 or 29,97)

 and

keyframe interval (I guess measured in seconds after the last keyframe .e.g 50 or 200):

What are the corresponding cmdline parameters for ffmpeg?

How can I tell ffmpeg to use the same values as the input?

Thank you
Ben
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Re: Parameters for "framerate" and "keyframe interval"?

Gyan Doshi
In reply to this post by Ben Stover
On Fri, Oct 26, 2018 at 3:22 PM Ben <[hidden email]>
wrote:

> For video codec H.264 there are two parameters:
>
> Framerate (e.g. 25 or 30 or 29,97)
>
>   and
>
> keyframe interval (I guess measured in seconds after the last keyframe
> .e.g 50 or 200):
>
> What are the corresponding cmdline parameters for ffmpeg?
>
> How can I tell ffmpeg to use the same values as the input?
>

FFmpeg will use the same framerate as the input stream, unless the user
overrides it, using `-r` or `fps` or a few other filters

Usually there is no point in mimicking the source keyframe placement. The
encoder will place keyframes as is optimal. But if you insist, add
`-force_key_frames source`. You can also force a fixed keyframe interval
using `-g N` where N is measured in frames (not seconds).

Gyan
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