[x265] Adaptove GoP sizes - not sure if its working

[Xinyue Lu]

On Wed, Oct 7, 2015 at 12:47 PM, Steve Borho <steve at borho.org> wrote:
> On 10/07, Xinyue Lu wrote:
>
> this blanket statement is incorrect. If the scene cut happens a large
> distance from the max keyframe interval it is better to encode it as a P
> to save bits. When you specify --keyint-max 250, the encoder will try to
> only use one I frame per 250 frames, this is its goal.

Yes, understand that, you are right.

I haven't had a chance to test the latest version, maybe will do it in
this weekend. In previous tests, it produced fixed length gop from the
beginning to the end, all the way through half hour video clips, so
that was certainly a bug.

I'll also test with different rc-lookahead settings to see the impact
of these patches.

Thanks.

>
> If there are scene cuts near the max keyframe interval that are not
> being set to I, then that could be a problem. The bias algorithm does
> tend to detect many possible scene cuts near the end of the max interval
> and this tends to trigger the flash detection logic (where you have many
> scene cut frames in a row) which defers the I frame until the end of the
> flash or max interval (see scenecut.cpp line 1450) It's not possible to
> tell if this is happening in your case without seeing the input video.
>
> --
> Steve Borho
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