From f998a618bac1f61586a3625620e0794c1abba04c Mon Sep 17 00:00:00 2001
From: Niklas Haas <git@haasn.dev>
Date: Thu, 15 Jun 2023 13:36:20 +0200
Subject: [PATCH] lavfi/vf_libplacebo: add nb_inputs option

To control the number of inputs.
---
 doc/filters.texi            |  5 +++++
 libavfilter/vf_libplacebo.c | 25 ++++++++++++++-----------
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 366dc53b79..f596773af6 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -16224,6 +16224,11 @@ to preserve the source colorimetry and size as best as it can, but it will
 apply any embedded film grain, dolby vision metadata or anamorphic SAR present
 in source frames.
 @table @option
+@item inputs
+Set the number of inputs. This can be used, alongside the @code{idx} variable,
+to allow placing/blending multiple inputs inside the output frame. This
+effectively enables functionality similar to @ref{hstack}, @ref{overlay}, etc.
+
 @item w
 @item h
 Set the output video dimension expression. Default values are @code{iw} and
diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
index 09a24e7c29..056041d213 100644
--- a/libavfilter/vf_libplacebo.c
+++ b/libavfilter/vf_libplacebo.c
@@ -502,6 +502,7 @@ static int parse_shader(AVFilterContext *avctx, const void *shader, size_t len)
 }
 
 static void libplacebo_uninit(AVFilterContext *avctx);
+static int libplacebo_config_input(AVFilterLink *inlink);
 
 static int libplacebo_init(AVFilterContext *avctx)
 {
@@ -530,6 +531,17 @@ static int libplacebo_init(AVFilterContext *avctx)
         s->out_format = AV_PIX_FMT_NONE;
     }
 
+    for (int i = 0; i < s->nb_inputs; i++) {
+        AVFilterPad pad = {
+            .name         = av_asprintf("input%d", i),
+            .type         = AVMEDIA_TYPE_VIDEO,
+            .config_props = &libplacebo_config_input,
+        };
+        if (!pad.name)
+            return AVERROR(ENOMEM);
+        RET(ff_append_inpad_free_name(avctx, &pad));
+    }
+
     RET(update_settings(avctx));
     RET(av_expr_parse(&s->crop_x_pexpr, s->crop_x_expr, var_names,
                       NULL, NULL, NULL, NULL, 0, s));
@@ -665,7 +677,6 @@ static int init_vulkan(AVFilterContext *avctx, const AVVulkanDeviceContext *hwct
     }
 
     /* Initialize inputs */
-    s->nb_inputs = 1;
     s->inputs = av_calloc(s->nb_inputs, sizeof(*s->inputs));
     if (!s->inputs)
         return AVERROR(ENOMEM);
@@ -1252,6 +1263,7 @@ fail:
 #define DYNAMIC (STATIC | AV_OPT_FLAG_RUNTIME_PARAM)
 
 static const AVOption libplacebo_options[] = {
+    { "inputs", "Number of inputs", OFFSET(nb_inputs), AV_OPT_TYPE_INT, {.i64 = 1}, 1, INT_MAX, .flags = STATIC },
     { "w", "Output video frame width",  OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, .flags = STATIC },
     { "h", "Output video frame height", OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, .flags = STATIC },
     { "fps", "Output video frame rate", OFFSET(fps_string), AV_OPT_TYPE_STRING, {.str = "none"}, .flags = STATIC },
@@ -1443,14 +1455,6 @@ static const AVOption libplacebo_options[] = {
 
 AVFILTER_DEFINE_CLASS(libplacebo);
 
-static const AVFilterPad libplacebo_inputs[] = {
-    {
-        .name         = "default",
-        .type         = AVMEDIA_TYPE_VIDEO,
-        .config_props = &libplacebo_config_input,
-    },
-};
-
 static const AVFilterPad libplacebo_outputs[] = {
     {
         .name         = "default",
@@ -1467,10 +1471,9 @@ const AVFilter ff_vf_libplacebo = {
     .uninit         = &libplacebo_uninit,
     .activate       = &libplacebo_activate,
     .process_command = &libplacebo_process_command,
-    FILTER_INPUTS(libplacebo_inputs),
     FILTER_OUTPUTS(libplacebo_outputs),
     FILTER_QUERY_FUNC(libplacebo_query_format),
     .priv_class     = &libplacebo_class,
     .flags_internal = FF_FILTER_FLAG_HWFRAME_AWARE,
-    .flags          = AVFILTER_FLAG_HWDEVICE,
+    .flags          = AVFILTER_FLAG_HWDEVICE | AVFILTER_FLAG_DYNAMIC_INPUTS,
 };