[FFmpeg-devel] [PATCH] separatefields filter

Clément Bœsch ubitux at gmail.com
Tue Apr 9 19:36:16 CEST 2013


On Tue, Apr 09, 2013 at 05:09:17PM +0000, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  doc/filters.texi                |  10 ++++
>  libavfilter/Makefile            |   1 +
>  libavfilter/allfilters.c        |   1 +
>  libavfilter/vf_separatefields.c | 108 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 120 insertions(+)
>  create mode 100644 libavfilter/vf_separatefields.c
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 483d8a1..8172a44 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -4896,6 +4896,16 @@ scale='min(500\, iw*3/2):-1'
>  @end example
>  @end itemize
>  
> + at section separatefields
> +
> +Separate fields takes a frame-based video input and splits each frame

"Separate fields" doesn't make much sense as name, maybe use
@code{separatefields}/

> +into its components fields, producing a new half height clip with
> +twice the frame rate and twice the frame count.
> +
> +This filter use field-dominance information in frame to decide which
> +of each pair of fields to place first in the output.
> +If it gets it wrong use @code{setfield} filter before @code{separatefields} filter.
> +

You could add an @anchor{setfield} above the appropriate section if not
present, and use @ref{setfield}; it's handy for users to be able to jump
directly to it, at least in html form.

>  @section setdar, setsar
>  
>  The @code{setdar} filter sets the Display Aspect Ratio for the filter
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index e1eb35d..d91529d 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -148,6 +148,7 @@ OBJS-$(CONFIG_PERMS_FILTER)                  += f_perms.o
>  OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
>  OBJS-$(CONFIG_PP_FILTER)                     += vf_pp.o
>  OBJS-$(CONFIG_REMOVELOGO_FILTER)             += bbox.o lswsutils.o lavfutils.o vf_removelogo.o
> +OBJS-$(CONFIG_SEPARATEFIELDS_FILTER)         += vf_separatefields.o
>  OBJS-$(CONFIG_SCALE_FILTER)                  += vf_scale.o
>  OBJS-$(CONFIG_SELECT_FILTER)                 += f_select.o
>  OBJS-$(CONFIG_SENDCMD_FILTER)                += f_sendcmd.o
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 4972322..e5c20ed 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -146,6 +146,7 @@ void avfilter_register_all(void)
>      REGISTER_FILTER(SCALE,          scale,          vf);
>      REGISTER_FILTER(SELECT,         select,         vf);
>      REGISTER_FILTER(SENDCMD,        sendcmd,        vf);
> +    REGISTER_FILTER(SEPARATEFIELDS, separatefields, vf);
>      REGISTER_FILTER(SETDAR,         setdar,         vf);
>      REGISTER_FILTER(SETFIELD,       setfield,       vf);
>      REGISTER_FILTER(SETPTS,         setpts,         vf);
> diff --git a/libavfilter/vf_separatefields.c b/libavfilter/vf_separatefields.c
> new file mode 100644
> index 0000000..ac4a1e8
> --- /dev/null
> +++ b/libavfilter/vf_separatefields.c
> @@ -0,0 +1,108 @@
> +/*
> + * Copyright (c) 2013 Paul B Mahol
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "libavutil/pixdesc.h"
> +#include "avfilter.h"
> +#include "internal.h"
> +
> +typedef struct {
> +    int nb_planes;
> +} SeparateFieldsContext;
> +
> +static int config_props_output(AVFilterLink *outlink)
> +{
> +    AVFilterContext *ctx = outlink->src;
> +    SeparateFieldsContext *sf = ctx->priv;
> +    AVFilterLink *inlink = ctx->inputs[0];
> +
> +    sf->nb_planes = av_pix_fmt_count_planes(inlink->format);;
> +
> +    if (inlink->h & 1) {
> +        av_log(ctx, AV_LOG_ERROR, "height must be even\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    outlink->time_base.num = inlink->time_base.num;
> +    outlink->time_base.den = inlink->time_base.den * 2;
> +    outlink->frame_rate.num = inlink->frame_rate.num * 2;
> +    outlink->frame_rate.den = inlink->frame_rate.den;
> +    outlink->w = inlink->w;
> +    outlink->h = inlink->h / 2;
> +
> +    return 0;
> +}
> +
> +static int filter_frame(AVFilterLink *inlink, AVFrame *inpicref)
> +{
> +    AVFilterContext *ctx = inlink->dst;
> +    SeparateFieldsContext *sf = ctx->priv;
> +    AVFilterLink *outlink = ctx->outputs[0];
> +    AVFrame *second;
> +    int i, ret;
> +
> +    inpicref->height = outlink->h;
> +    inpicref->interlaced_frame = 0;
> +
> +    second = av_frame_clone(inpicref);
> +    if (!second)
> +        return AVERROR(ENOMEM);
> +
> +    for (i = 0; i < sf->nb_planes; i++) {
> +        if (!inpicref->top_field_first)
> +            inpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
> +        else
> +            second->data[i] = second->data[i] + second->linesize[i];
> +        inpicref->linesize[i] = 2 * inpicref->linesize[i];
> +        second->linesize[i]   = 2 * second->linesize[i];

*= 2

> +    }
> +
> +    inpicref->pts *= 2;
> +    second->pts    = inpicref->pts + 1;
> +

I wonder if that will really be accurate.

> +    ret = ff_filter_frame(outlink, inpicref);
> +    return ff_filter_frame(outlink, second) | ret;

if both fails differently, the error code will make no sense.

> +}
> +
> +static const AVFilterPad separatefields_inputs[] = {
> +    {
> +        .name             = "default",
> +        .type             = AVMEDIA_TYPE_VIDEO,

> +        .get_video_buffer = ff_null_get_video_buffer,

Does this make any difference?

> +        .filter_frame     = filter_frame,
> +    },
> +    { NULL }
> +};
> +
> +static const AVFilterPad separatefields_outputs[] = {
> +    {
> +        .name          = "default",
> +        .type          = AVMEDIA_TYPE_VIDEO,
> +        .config_props  = config_props_output,
> +    },
> +    { NULL }
> +};
> +
> +AVFilter avfilter_vf_separatefields = {
> +    .name          = "separatefields",
> +    .description   = NULL_IF_CONFIG_SMALL("Split input video frames into fields."),
> +    .priv_size     = sizeof(SeparateFieldsContext),
> +    .inputs        = separatefields_inputs,
> +    .outputs       = separatefields_outputs,
> +};

Rest LGTM. Don't forget the Changelog entry.

-- 
Clément B.
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