[cogl] cogl-gst-video-sink: Premultiply the colors coming from the video

[Neil Roberts <nroberts src gnome org>]

commit 07a57f26596c72507035369c90ed6d62568330b5
Author: Neil Roberts <neil linux intel com>
Date:   Wed Jan 22 15:11:55 2014 +0000

    cogl-gst-video-sink: Premultiply the colors coming from the video
    
    Commit 99a53c82e9ab0a1e5 removed the internal format argument when
    uploading a video frame to a texture so that the format will just be
    determined automatically from the image format. However this also
    leaves the premultiplied state at the default and the default is TRUE.
    That means that when we upload RGBA data Cogl will do a premultiplied
    conversion on the CPU. We probably don't want to be putting a CPU
    conversion in the way of video frames so this patch changes it to set
    the premultiplied state to FALSE on the textures and then do the
    premultiplied conversion in the shader.
    
    This is particularly important for AYUV which uses the alpha channel
    for the V component so doing a premultiplied conversion on the CPU
    just creates garbage and messes up the image.
    
    The RGB and RGBA renderers have each been split into two; one that
    uses GLSL and one that uses a regular pipeline. The RGBA pipeline
    without GLSL is then changed to use 2 layers so we that we can do the
    premultiplied conversion in the second layer with a special layer
    combine string.
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 cogl-gst/cogl-gst-video-sink.c |  159 ++++++++++++++++++++++++++++++---------
 cogl-gst/cogl-gst-video-sink.h |    4 +-
 2 files changed, 125 insertions(+), 38 deletions(-)
---
diff --git a/cogl-gst/cogl-gst-video-sink.c b/cogl-gst/cogl-gst-video-sink.c
index f9887aa..243d9ae 100644
--- a/cogl-gst/cogl-gst-video-sink.c
+++ b/cogl-gst/cogl-gst-video-sink.c
@@ -417,40 +417,6 @@ clear_frame_textures (CoglGstVideoSink *sink)
   priv->frame_dirty = TRUE;
 }
 
-static void
-cogl_gst_rgb_setup_pipeline (CoglGstVideoSink *sink,
-                             CoglPipeline *pipeline)
-{
-  CoglGstVideoSinkPrivate *priv = sink->priv;
-
-  if (cogl_has_feature (priv->ctx, COGL_FEATURE_ID_GLSL))
-    {
-      static SnippetCache snippet_cache;
-      SnippetCacheEntry *entry = get_cache_entry (sink, &snippet_cache);
-
-      if (entry == NULL)
-        {
-          char *source;
-
-          source =
-            g_strdup_printf ("vec4\n"
-                             "cogl_gst_sample_video%i (vec2 UV)\n"
-                             "{\n"
-                             "  return texture2D (cogl_sampler%i, UV);\n"
-                             "}\n",
-                             priv->custom_start,
-                             priv->custom_start);
-
-          entry = add_cache_entry (sink, &snippet_cache, source);
-          g_free (source);
-        }
-
-      setup_pipeline_from_cache_entry (sink, pipeline, entry, 1);
-    }
-  else
-    setup_pipeline_from_cache_entry (sink, pipeline, NULL, 1);
-}
-
 static inline CoglBool
 is_pot (unsigned int number)
 {
@@ -504,9 +470,46 @@ video_texture_new_from_data (CoglContext *ctx,
 
   cogl_object_unref (bitmap);
 
+  cogl_texture_set_premultiplied (tex, FALSE);
+
   return tex;
 }
 
+static void
+cogl_gst_rgb24_glsl_setup_pipeline (CoglGstVideoSink *sink,
+                                    CoglPipeline *pipeline)
+{
+  CoglGstVideoSinkPrivate *priv = sink->priv;
+  static SnippetCache snippet_cache;
+  SnippetCacheEntry *entry = get_cache_entry (sink, &snippet_cache);
+
+  if (entry == NULL)
+    {
+      char *source;
+
+      source =
+        g_strdup_printf ("vec4\n"
+                         "cogl_gst_sample_video%i (vec2 UV)\n"
+                         "{\n"
+                         "  return texture2D (cogl_sampler%i, UV);\n"
+                         "}\n",
+                         priv->custom_start,
+                         priv->custom_start);
+
+      entry = add_cache_entry (sink, &snippet_cache, source);
+      g_free (source);
+    }
+
+  setup_pipeline_from_cache_entry (sink, pipeline, entry, 1);
+}
+
+static void
+cogl_gst_rgb24_setup_pipeline (CoglGstVideoSink *sink,
+                               CoglPipeline *pipeline)
+{
+  setup_pipeline_from_cache_entry (sink, pipeline, NULL, 1);
+}
+
 static CoglBool
 cogl_gst_rgb24_upload (CoglGstVideoSink *sink,
                        GstBuffer *buffer)
@@ -542,6 +545,17 @@ map_fail:
   }
 }
 
+static CoglGstRenderer rgb24_glsl_renderer =
+{
+  "RGB 24",
+  COGL_GST_RGB24,
+  COGL_GST_RENDERER_NEEDS_GLSL,
+  GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("{ RGB, BGR }")),
+  1, /* n_layers */
+  cogl_gst_rgb24_glsl_setup_pipeline,
+  cogl_gst_rgb24_upload,
+};
+
 static CoglGstRenderer rgb24_renderer =
 {
   "RGB 24",
@@ -549,10 +563,61 @@ static CoglGstRenderer rgb24_renderer =
   0,
   GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("{ RGB, BGR }")),
   1, /* n_layers */
-  cogl_gst_rgb_setup_pipeline,
+  cogl_gst_rgb24_setup_pipeline,
   cogl_gst_rgb24_upload,
 };
 
+static void
+cogl_gst_rgb32_glsl_setup_pipeline (CoglGstVideoSink *sink,
+                                    CoglPipeline *pipeline)
+{
+  CoglGstVideoSinkPrivate *priv = sink->priv;
+  static SnippetCache snippet_cache;
+  SnippetCacheEntry *entry = get_cache_entry (sink, &snippet_cache);
+
+  if (entry == NULL)
+    {
+      char *source;
+
+      source =
+        g_strdup_printf ("vec4\n"
+                         "cogl_gst_sample_video%i (vec2 UV)\n"
+                         "{\n"
+                         "  vec4 color = texture2D (cogl_sampler%i, UV);\n"
+                         /* Premultiply the color */
+                         "  color.rgb *= color.a;\n"
+                         "  return color;\n"
+                         "}\n",
+                         priv->custom_start,
+                         priv->custom_start);
+
+      entry = add_cache_entry (sink, &snippet_cache, source);
+      g_free (source);
+    }
+
+  setup_pipeline_from_cache_entry (sink, pipeline, entry, 1);
+}
+
+static void
+cogl_gst_rgb32_setup_pipeline (CoglGstVideoSink *sink,
+                               CoglPipeline *pipeline)
+{
+  CoglGstVideoSinkPrivate *priv = sink->priv;
+  char *layer_combine;
+
+  setup_pipeline_from_cache_entry (sink, pipeline, NULL, 1);
+
+  /* Premultiply the texture using the a special layer combine */
+  layer_combine = g_strdup_printf ("RGB=MODULATE(PREVIOUS, TEXTURE_%i[A])\n"
+                                   "A=REPLACE(PREVIOUS[A])",
+                                   priv->custom_start);
+  cogl_pipeline_set_layer_combine (pipeline,
+                                   priv->custom_start + 1,
+                                   layer_combine,
+                                   NULL);
+  g_free(layer_combine);
+}
+
 static CoglBool
 cogl_gst_rgb32_upload (CoglGstVideoSink *sink,
                        GstBuffer *buffer)
@@ -588,14 +653,25 @@ map_fail:
   }
 }
 
+static CoglGstRenderer rgb32_glsl_renderer =
+{
+  "RGB 32",
+  COGL_GST_RGB32,
+  COGL_GST_RENDERER_NEEDS_GLSL,
+  GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("{ RGBA, BGRA }")),
+  1, /* n_layers */
+  cogl_gst_rgb32_glsl_setup_pipeline,
+  cogl_gst_rgb32_upload,
+};
+
 static CoglGstRenderer rgb32_renderer =
 {
   "RGB 32",
   COGL_GST_RGB32,
   0,
   GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("{ RGBA, BGRA }")),
-  1, /* n_layers */
-  cogl_gst_rgb_setup_pipeline,
+  2, /* n_layers */
+  cogl_gst_rgb32_setup_pipeline,
   cogl_gst_rgb32_upload,
 };
 
@@ -778,6 +854,8 @@ cogl_gst_ayuv_glsl_setup_pipeline (CoglGstVideoSink *sink,
                            "  color.r = y + 1.59765625 * v;\n"
                            "  color.g = y - 0.390625 * u - 0.8125 * v;\n"
                            "  color.b = y + 2.015625 * u;\n"
+                           /* Premultiply the color */
+                           "  color.rgb *= color.a;\n"
                            "  return color;\n"
                            "}\n", priv->custom_start,
                            priv->custom_start);
@@ -838,8 +916,13 @@ cogl_gst_build_renderers_list (CoglContext *ctx)
   int i;
   static CoglGstRenderer *const renderers[] =
   {
+    /* These are in increasing order of priority so that the
+     * priv->renderers will be in decreasing order. That way the GLSL
+     * renderers will be preferred if they are available */
     &rgb24_renderer,
     &rgb32_renderer,
+    &rgb24_glsl_renderer,
+    &rgb32_glsl_renderer,
     &yv12_glsl_renderer,
     &i420_glsl_renderer,
     &ayuv_glsl_renderer,
@@ -916,6 +999,8 @@ cogl_gst_find_renderer_by_format (CoglGstVideoSink *sink,
   CoglGstRenderer *renderer = NULL;
   GSList *element;
 
+  /* The renderers list is in decreasing order of priority so we'll
+   * pick the first one that matches */
   for (element = priv->renderers; element; element = g_slist_next (element))
     {
       CoglGstRenderer *candidate = (CoglGstRenderer *) element->data;
diff --git a/cogl-gst/cogl-gst-video-sink.h b/cogl-gst/cogl-gst-video-sink.h
index 87e7953..3c11be7 100644
--- a/cogl-gst/cogl-gst-video-sink.h
+++ b/cogl-gst/cogl-gst-video-sink.h
@@ -78,7 +78,9 @@
  * called cogl_gst_sample_video0 which takes a single vec2 argument.
  * This can be used by custom snippets set the by the application to
  * sample from the video. The vec2 argument represents the normalised
- * coordinates within the video.
+ * coordinates within the video. The function returns a vec4
+ * containing a pre-multiplied RGBA color of the pixel within the
+ * video.
  *
  * Since: 1.16
  */