[x265] [PATCH] modify the minimum keyint value

[Pradeep Ramachandran]

Deepthi,
The behavior of scene-cut doesn't change in anyway. For closed-gop, if a
scenecut is detected beyond min-keyint, an IDR frame is introduced, else, a
non-IDR I-frame is introduced. Like Tom mentioned, disabling the automatic
clipping of min-keyint enables x265 to guarantee a fixed-GOP length
(between IDR-frames) when min-keyint is set to keyint even with
scenecut-enabled. From our experiments, this seems to give better encoding
efficiency than turning off scencut detection to guarantee fixed GOP
lengths.

Pradeep.

On Tue, Sep 27, 2016 at 12:39 AM, Tom Vaughan <
tom.vaughan at multicorewareinc.com> wrote:

> We concluded that it doesn’t make sense to prevent the ability to encode
> with a fixed GOP size, regardless of whether or not a user wants scenecut
> enabled.  This patch enables users to specify a min-keyint that is equal to
> keyint (a fixed keyint) that x265 does not override.  Separately, we’ve
> also fixed our scenecut option to enable the benefits of scenecut detection
> with fixed GOP structures.
>
>
>
> *From:* x265-devel [mailto:x265-devel-bounces at videolan.org] *On Behalf Of
> *Deepthi Nandakumar
> *Sent:* Monday, September 26, 2016 12:01 PM
> *To:* Development for x265
> *Subject:* Re: [x265] [PATCH] modify the minimum keyint value
>
>
>
> Earlier, keyframeMin was fixed to the range (1, keyframeMax/2 + 1). This
> patch removes the upper bound, but does not change behaviour wrt scenecut
> threshold in any way.
>
>
>
> On Thu, Sep 22, 2016 at 3:14 AM, <gopi.satykrishna at multicorewareinc.com>
> wrote:
>
> # HG changeset patch
> # User Gopi Satykrishna Akisetty <gopi.satykrishna at multicorewareinc.com>
> # Date 1474539223 -19800
> #      Thu Sep 22 15:43:43 2016 +0530
> # Node ID 24ecccf7b435e849545e161a0992f452875f6bbc
> # Parent  bdf098eefd35b70b68419f5a204e60f1df4aeae1
> modify the minimum keyint value
>
> This patch enables fixed gop size even when scenecut option is enabled
>
> diff -r bdf098eefd35 -r 24ecccf7b435 doc/reST/cli.rst
> --- a/doc/reST/cli.rst  Thu Sep 22 13:26:57 2016 +0530
> +++ b/doc/reST/cli.rst  Thu Sep 22 15:43:43 2016 +0530
> @@ -1141,10 +1141,10 @@
>  .. option:: --min-keyint, -i <integer>
>
>         Minimum GOP size. Scenecuts closer together than this are coded as
> I
> -       or P, not IDR. Minimum keyint is clamped to be at least half of
> -       :option:`--keyint`. If you wish to force regular keyframe intervals
> +       or P, not IDR. If you wish to force regular keyframe intervals
>         and disable adaptive I frame placement, you must use
> -       :option:`--no-scenecut`.
> +       :option:`--no-scenecut` or give minimum keyint equal to keyint
> +       with scenecut enabled.
>
>         **Range of values:** >=0 (0: auto)
>
> diff -r bdf098eefd35 -r 24ecccf7b435 source/encoder/encoder.cpp
> --- a/source/encoder/encoder.cpp        Thu Sep 22 13:26:57 2016 +0530
> +++ b/source/encoder/encoder.cpp        Thu Sep 22 15:43:43 2016 +0530
> @@ -1660,7 +1660,7 @@
>          double fps = (double)p->fpsNum / p->fpsDenom;
>          p->keyframeMin = X265_MIN((int)fps, p->keyframeMax / 10);
>      }
> -    p->keyframeMin = X265_MAX(1, X265_MIN(p->keyframeMin, p->keyframeMax
> / 2 + 1));
> +    p->keyframeMin = X265_MAX(1, p->keyframeMin);
>
>      if (!p->bframes)
>          p->bBPyramid = 0;
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
>
>
>
>
> --
>
> Deepthi
>
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20160927/6b6e2d37/attachment-0001.html>