[x264-devel] regular intra period

[Jason Garrett-Glaser]

On Wed, Mar 11, 2009 at 3:11 AM,  <Peter.List at telekom.de> wrote:
>
>
>> On Wed, Mar 11, 2009 at 2:52 AM,  <Peter.List at telekom.de> wrote:
>> >
>> >
>> > ...
>> >> x264 will only generate non-IDR I-frames in the case that it detects a
>> >> scenecut but it has been less than --min-keyint since the previous
>> >> keyframe.  All non-scenecut I-frames are IDR.
>> >>
>> >> Dark Shikari
>> >
>> > Hi Jason,
>> > I am wondering, what's the idea behind the fact that scene cuts are NOT
>> > made IDR.
>>
>> That is not what I said.  Read my email again, in particular, the
>> phrase starting with the word "but."
>>
>> Dark Shikari
>
> Ok... I guess the "but" means (logical) AND. I still don't understand though, what's the advantage for a non IDR frame in this case.

If the user has specified a minimum keyframe interval that would
prohibit an IDR frame at the current scenecut, the encoder has *NO
CHOICE* but to not use an IDR frame!

Also, see the case of single-frame flashes and such that could
theoretically result in a ton of sequential IDR frames, which would be
bad (and clear the reference list repeatedly).

> Also, for a MPEG2 style GOP-structure with a key frame interval of 24 frames, what would be your preferred number for --min-keyint?

Probably 2.

Dark Shikari