[FFmpeg-devel] [PATCH] avfilter: port qp filter from libmpcodecs

Paul B Mahol onemda at gmail.com
Thu Sep 19 12:49:41 CEST 2013


On 9/19/13, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Wed, Sep 18, 2013 at 11:57:55PM +0000, Paul B Mahol wrote:
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  doc/filters.texi         |  32 ++++++++++
>>  libavfilter/Makefile     |   1 +
>>  libavfilter/allfilters.c |   1 +
>>  libavfilter/vf_qp.c      | 152
>> +++++++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 186 insertions(+)
>>  create mode 100644 libavfilter/vf_qp.c
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 915f310..127885a 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -6236,6 +6236,38 @@ The main purpose of setting @option{mp} to a chroma
>> plane is to reduce CPU
>>  load and make pullup usable in realtime on slow machines.
>>  @end table
>>
>> + at section qp
>> +
>> +Change video quantization parameters (QP).
>> +
>> +The filter accepts the following option:
>> +
>> + at table @option
>> + at item qp
>> +Set expression for quantization parameter.
>> + at end table
>> +
>> +The expression is evaluated through the eval API and can contain, among
>> others,
>> +the following constants:
>> +
>> + at table @var
>> + at item known
>> +1 if index is not 129, 0 otherwise.
>> +
>> + at item qp
>> +Sequentional index starting from -129 to 128.
>> + at end table
>> +
>> + at subsection Examples
>> +
>> + at itemize
>> + at item
>> +Some equation like:
>> + at example
>> +qp=2+2*sin(PI*qp)
>> + at end example
>> + at end itemize
>> +
>>  @section removelogo
>>
>>  Suppress a TV station logo, using an image file to determine which
>> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
>> index 198bf4c..5dc8389 100644
>> --- a/libavfilter/Makefile
>> +++ b/libavfilter/Makefile
>> @@ -174,6 +174,7 @@ OBJS-$(CONFIG_PIXDESCTEST_FILTER)            +=
>> vf_pixdesctest.o
>>  OBJS-$(CONFIG_PP_FILTER)                     += vf_pp.o
>>  OBJS-$(CONFIG_PSNR_FILTER)                   += vf_psnr.o dualinput.o
>>  OBJS-$(CONFIG_PULLUP_FILTER)                 += vf_pullup.o
>> +OBJS-$(CONFIG_QP_FILTER)                     += vf_qp.o
>>  OBJS-$(CONFIG_REMOVELOGO_FILTER)             += bbox.o lswsutils.o
>> lavfutils.o vf_removelogo.o
>>  OBJS-$(CONFIG_ROTATE_FILTER)                 += vf_rotate.o
>>  OBJS-$(CONFIG_SEPARATEFIELDS_FILTER)         += vf_separatefields.o
>> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
>> index 2825304..69e6cab 100644
>> --- a/libavfilter/allfilters.c
>> +++ b/libavfilter/allfilters.c
>> @@ -169,6 +169,7 @@ void avfilter_register_all(void)
>>      REGISTER_FILTER(PP,             pp,             vf);
>>      REGISTER_FILTER(PSNR,           psnr,           vf);
>>      REGISTER_FILTER(PULLUP,         pullup,         vf);
>> +    REGISTER_FILTER(QP,             qp,             vf);
>>      REGISTER_FILTER(REMOVELOGO,     removelogo,     vf);
>>      REGISTER_FILTER(ROTATE,         rotate,         vf);
>>      REGISTER_FILTER(SAB,            sab,            vf);
>> diff --git a/libavfilter/vf_qp.c b/libavfilter/vf_qp.c
>> new file mode 100644
>> index 0000000..67fe2ec
>> --- /dev/null
>> +++ b/libavfilter/vf_qp.c
>> @@ -0,0 +1,152 @@
>> +/*
>> + * Copyright (C) 2004 Michael Niedermayer <michaelni at gmx.at>
>> + *
>> + * 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 <math.h>
>> +#include "libavutil/eval.h"
>> +#include "libavutil/imgutils.h"
>> +#include "libavutil/pixdesc.h"
>> +#include "libavutil/opt.h"
>> +#include "avfilter.h"
>> +#include "formats.h"
>> +#include "internal.h"
>> +#include "video.h"
>> +
>> +typedef struct QPContext {
>> +    const AVClass *class;
>> +    char *qp_expr_str;
>> +    int8_t lut[257];
>> +    int h, qstride;
>> +} QPContext;
>> +
>> +#define OFFSET(x) offsetof(QPContext, x)
>> +#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
>> +
>> +static const AVOption qp_options[] = {
>> +    { "qp", "set qp expression", OFFSET(qp_expr_str), AV_OPT_TYPE_STRING,
>> {.str=NULL}, 0, 0, FLAGS },
>> +    { NULL }
>> +};
>> +
>> +AVFILTER_DEFINE_CLASS(qp);
>> +
>> +static int config_input(AVFilterLink *inlink)
>> +{
>> +    AVFilterContext *ctx = inlink->dst;
>> +    QPContext *s = ctx->priv;
>> +    int i;
>> +
>> +    if (!s->qp_expr_str)
>> +        return 0;
>> +
>> +    s->h       = (inlink->h + 15) >> 4;
>> +    s->qstride = (inlink->w + 15) >> 4;
>> +    for (i = -129; i < 128; i++) {
>> +        double var_values[] = { i != -129, i, 0 };
>> +        static const char *var_names[] = { "known", "qp", NULL };
>> +        double temp_val;
>> +        int ret;
>> +
>> +        ret = av_expr_parse_and_eval(&temp_val, s->qp_expr_str,
>> +                                     var_names, var_values,
>> +                                     NULL, NULL, NULL, NULL, 0, 0, ctx);
>> +        if (ret < 0)
>> +            return ret;
>> +
>> +        s->lut[i + 129] = lrintf(temp_val);
>> +    }
>
> it could make sense to allow forcing the evaluating the expression for
> each macroblock
> that way it could be used to do spatial or temporal smoothing,
> depend on frame number of do add a random value

Gread idea, but becaues I can't compare it with broken mp=qp, I want to know
is current code (use of API) correct?

This patch is not about adding new (non-trivial/easy) features, one
can do it freely later.

>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Many things microsoft did are stupid, but not doing something just because
> microsoft did it is even more stupid. If everything ms did were stupid they
> would be bankrupt already.
>


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