avfilter: port qp filter from libmpcodecs

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/filters.texi

@@ -7351,6 +7351,38 @@ telecine NTSC input:
 ffmpeg -i input -vf pullup -r 24000/1001 ...
 @end example
 
+@section qp
+
+Change video quantization parameters (QP).
+
+The filter accepts the following option:
+
+@table @option
+@item qp
+Set expression for quantization parameter.
+@end table
+
+The expression is evaluated through the eval API and can contain, among others,
+the following constants:
+
+@table @var
+@item known
+1 if index is not 129, 0 otherwise.
+
+@item qp
+Sequentional index starting from -129 to 128.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Some equation like:
+@example
+qp=2+2*sin(PI*qp)
+@end example
+@end itemize
+
 @section removelogo
 
 Suppress a TV station logo, using an image file to determine which

libavfilter/Makefile

@@ -167,6 +167,7 @@ OBJS-$(CONFIG_PP_FILTER)                     += vf_pp.o
 OBJS-$(CONFIG_PP7_FILTER)                    += vf_pp7.o
 OBJS-$(CONFIG_PSNR_FILTER)                   += vf_psnr.o dualinput.o framesync.o
 OBJS-$(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

libavfilter/allfilters.c

@@ -182,6 +182,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(PP7,            pp7,            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);

libavfilter/vf_qp.c

@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2004 Michael Niedermayer <michaelni@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);
+    }
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    QPContext *s = ctx->priv;
+    AVBufferRef *out_qp_table_buf;
+    AVFrame *out;
+    const int8_t *in_qp_table;
+    int type, stride, ret;
+
+    if (!s->qp_expr_str || ctx->is_disabled)
+        return ff_filter_frame(outlink, in);
+
+    out_qp_table_buf = av_buffer_alloc(s->h * s->qstride);
+    if (!out_qp_table_buf) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    out = av_frame_clone(in);
+    if (!out) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    in_qp_table = av_frame_get_qp_table(in, &stride, &type);
+    av_frame_set_qp_table(out, out_qp_table_buf, s->qstride, type);
+
+    if (in_qp_table) {
+        int y, x;
+
+        for (y = 0; y < s->h; y++)
+            for (x = 0; x < s->qstride; x++)
+                out_qp_table_buf->data[x + s->qstride * y] = s->lut[129 +
+                    ((int8_t)in_qp_table[x + stride * y])];
+    } else {
+        int y, x, qp = s->lut[0];
+
+        for (y = 0; y < s->h; y++)
+            for (x = 0; x < s->qstride; x++)
+                out_qp_table_buf->data[x + s->qstride * y] = qp;
+    }
+
+    ret = ff_filter_frame(outlink, out);
+fail:
+    av_frame_free(&in);
+    return ret;
+}
+
+static const AVFilterPad qp_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+        .config_props = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad qp_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_qp = {
+    .name          = "qp",
+    .description   = NULL_IF_CONFIG_SMALL("Change video quantization parameters."),
+    .priv_size     = sizeof(QPContext),
+    .inputs        = qp_inputs,
+    .outputs       = qp_outputs,
+    .priv_class    = &qp_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL,
+};