[MEncoder-users] More frequent keyframes

[Rich Felker]

On Thu, Jul 14, 2005 at 03:24:20PM -0500, Pete Davis wrote:
> I set the keyint=30 in the lavcopts instead of using the default which gave
> me the effect I wanted in terms of better fast-forward/fast-reverse on my
> DSM-320.
> 
> The question I have is in regards to file size. I did two videos with the
> only difference is one was the keyint=30 and in the other, keyint was the
> default (250, I think). The resulting file sizes were very close.
> 
> My question is: Does this mean the overall video quality would be lower? I
> just looked at the same scene in both to get a general idea and didn't see a
> noticeable difference. 
> 
> Just curious how that works. I'm guessing that when you set the bitrate,
> it's going to manage to pack the video in that bitrate and that more
> keyframes would just mean that it's going to reduce the quality to
> compensate.

Yes. More keyframes with same bitrate == lower quality. Don't lower
keyint unless you have a specific reason for needing it low. The only
good reasons I know are VCD/DVD compliance (when encoding mpeg1/2 for
(S)VCD or DVD) and precision seeking.

Rich