video: Add new method for converting a video frame

https://bugzilla.gnome.org/show_bug.cgi?id=629157

docs/libs/gst-plugins-base-libs-sections.txt

@@ -1897,6 +1897,7 @@ gst_video_parse_caps_framerate
 gst_video_parse_caps_pixel_aspect_ratio
 gst_video_parse_caps_color_matrix
 gst_video_parse_caps_chroma_site
+gst_video_convert_frame
 </SECTION>
 
 <SECTION>

gst-libs/gst/video/Makefile.am

@@ -13,7 +13,7 @@ lib_LTLIBRARIES = libgstvideo-@GST_MAJORMINOR@.la
 CLEANFILES = $(BUILT_SOURCES)
 
 libgstvideo_@GST_MAJORMINOR@_la_SOURCES = \
-	video.c gstvideosink.c gstvideofilter.c
+	video.c gstvideosink.c gstvideofilter.c convertframe.c
 nodist_libgstvideo_@GST_MAJORMINOR@_la_SOURCES = $(BUILT_SOURCES)
 
 libgstvideo_@GST_MAJORMINOR@includedir = $(includedir)/gstreamer-@GST_MAJORMINOR@/gst/video

gst-libs/gst/video/convertframe.c

@@ -0,0 +1,304 @@
+/* Small helper element for format conversion
+ * Copyright (C) 2005 Tim-Philipp Müller <tim centricular net>
+ * Copyright (C) 2010 Brandon Lewis <brandon.lewis@collabora.co.uk>
+ * Copyright (C) 2010 Edward Hervey <edward.hervey@collabora.co.uk>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include <string.h>
+#include "video.h"
+
+static gboolean
+caps_are_raw (const GstCaps * caps)
+{
+  guint i, len;
+
+  len = gst_caps_get_size (caps);
+
+  for (i = 0; i < len; i++) {
+    GstStructure *st = gst_caps_get_structure (caps, i);
+    if (gst_structure_has_name (st, "video/x-raw-yuv") ||
+        gst_structure_has_name (st, "video/x-raw-rgb"))
+      return TRUE;
+  }
+
+  return FALSE;
+}
+
+static gboolean
+create_element (const gchar * factory_name, GstElement ** element,
+    GError ** err)
+{
+  *element = gst_element_factory_make (factory_name, NULL);
+  if (*element)
+    return TRUE;
+
+  if (err && *err == NULL) {
+    *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_MISSING_PLUGIN,
+        "cannot create element '%s' - please check your GStreamer installation",
+        factory_name);
+  }
+
+  return FALSE;
+}
+
+static GstElement *
+get_encoder (const GstCaps * caps, GError ** err)
+{
+  GList *encoders = NULL;
+  GList *filtered = NULL;
+  GstElementFactory *factory = NULL;
+  GstElement *encoder = NULL;
+
+  encoders =
+      gst_element_factory_list_get_elements (GST_ELEMENT_FACTORY_TYPE_ENCODER |
+      GST_ELEMENT_FACTORY_TYPE_MEDIA_IMAGE, GST_RANK_NONE);
+
+  if (encoders == NULL) {
+    *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_MISSING_PLUGIN,
+        "Cannot find any image encoder");
+    goto fail;
+  }
+
+  GST_INFO ("got factory list %p", encoders);
+  gst_plugin_feature_list_debug (encoders);
+
+  filtered =
+      gst_element_factory_list_filter (encoders, caps, GST_PAD_SRC, FALSE);
+  GST_INFO ("got filtered list %p", filtered);
+
+  if (filtered == NULL) {
+    gchar *tmp = gst_caps_to_string (caps);
+    *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_MISSING_PLUGIN,
+        "Cannot find any image encoder for caps %s", tmp);
+    g_free (tmp);
+    goto fail;
+  }
+
+  gst_plugin_feature_list_debug (filtered);
+
+  factory = (GstElementFactory *) filtered->data;
+
+  GST_INFO ("got factory %p", factory);
+  encoder = gst_element_factory_create (factory, NULL);
+
+  GST_INFO ("created encoder element %p, %s", encoder,
+      gst_element_get_name (encoder));
+
+fail:
+  if (encoders)
+    gst_plugin_feature_list_free (encoders);
+  if (filtered)
+    gst_plugin_feature_list_free (filtered);
+
+  return encoder;
+}
+
+/**
+ * gst_video_convert_frame:
+ * @buf: a #GstBuffer
+ * @to_caps: the #GstCaps to convert to
+ * @timeout: the maximum amount of time allowed for the processing.
+ * @err: pointer to a #GError. Can be %NULL.
+ *
+ * Converts a raw video buffer into the specified output caps.
+ *
+ * The output caps can be any raw video formats or any image formats (jpeg, png, ...).
+ *
+ * The width, height and pixel-aspect-ratio can also be specified in the output caps.
+ *
+ * Returns: The converted #GstBuffer, or %NULL if an error happened (in which case @err
+ * will point to the #GError).
+ */
+GstBuffer *
+gst_video_convert_frame (GstBuffer * buf, const GstCaps * to_caps,
+    GstClockTime timeout, GError ** err)
+{
+  GstElement *src = NULL, *csp = NULL, *vscale = NULL, *sink = NULL, *encoder =
+      NULL, *pipeline;
+  GstMessage *msg;
+  GstBuffer *result = NULL;
+  GError *error = NULL;
+  GstBus *bus;
+  GstCaps *from_caps;
+  GstFlowReturn ret;
+
+  g_return_val_if_fail (buf != NULL, NULL);
+  g_return_val_if_fail (to_caps != NULL, NULL);
+  g_return_val_if_fail (GST_BUFFER_CAPS (buf) != NULL, NULL);
+
+  from_caps = GST_BUFFER_CAPS (buf);
+
+  /* videoscale is here to correct for the pixel-aspect-ratio for us */
+  GST_DEBUG ("creating elements");
+  if (!create_element ("appsrc", &src, &error) ||
+      !create_element ("ffmpegcolorspace", &csp, &error) ||
+      !create_element ("videoscale", &vscale, &error) ||
+      !create_element ("appsink", &sink, &error))
+    goto no_elements;
+
+  pipeline = gst_pipeline_new ("videoconvert-pipeline");
+  if (pipeline == NULL)
+    goto no_pipeline;
+
+  /* Add black borders if necessary to keep the DAR */
+  g_object_set (vscale, "add-borders", TRUE, NULL);
+
+  GST_DEBUG ("adding elements");
+  gst_bin_add_many (GST_BIN (pipeline), src, csp, vscale, sink, NULL);
+
+  /* set caps */
+  g_object_set (src, "caps", from_caps, NULL);
+  g_object_set (sink, "caps", to_caps, NULL);
+
+  /* FIXME: linking is still way too expensive, profile this properly */
+  GST_DEBUG ("linking src->csp");
+  if (!gst_element_link_pads (src, "src", csp, "sink"))
+    goto link_failed;
+
+  GST_DEBUG ("linking csp->vscale");
+  if (!gst_element_link_pads (csp, "src", vscale, "sink"))
+    goto link_failed;
+
+  if (caps_are_raw (to_caps)) {
+    GST_DEBUG ("linking vscale->sink");
+
+    if (!gst_element_link_pads (vscale, "src", sink, "sink"))
+      goto link_failed;
+  } else {
+    encoder = get_encoder (to_caps, &error);
+    if (!encoder)
+      goto no_encoder;
+    gst_bin_add (GST_BIN (pipeline), encoder);
+
+    GST_DEBUG ("linking vscale->encoder");
+    if (!gst_element_link (vscale, encoder))
+      goto link_failed;
+
+    GST_DEBUG ("linking encoder->sink");
+    if (!gst_element_link_pads (encoder, "src", sink, "sink"))
+      goto link_failed;
+  }
+
+  /* now set the pipeline to the paused state, after we push the buffer into
+   * appsrc, this should preroll the converted buffer in appsink */
+  GST_DEBUG ("running conversion pipeline to caps %" GST_PTR_FORMAT, to_caps);
+  gst_element_set_state (pipeline, GST_STATE_PAUSED);
+
+  /* feed buffer in appsrc */
+  GST_DEBUG ("feeding buffer %p, size %u, caps %" GST_PTR_FORMAT,
+      buf, GST_BUFFER_SIZE (buf), from_caps);
+  g_signal_emit_by_name (src, "push-buffer", buf, &ret);
+
+  /* now see what happens. We either got an error somewhere or the pipeline
+   * prerolled */
+  bus = gst_element_get_bus (pipeline);
+  msg = gst_bus_timed_pop_filtered (bus,
+      timeout, GST_MESSAGE_ERROR | GST_MESSAGE_ASYNC_DONE);
+
+  if (msg) {
+    switch (GST_MESSAGE_TYPE (msg)) {
+      case GST_MESSAGE_ASYNC_DONE:
+      {
+        /* we're prerolled, get the frame from appsink */
+        g_signal_emit_by_name (sink, "pull-preroll", &result);
+
+        if (result) {
+          GST_DEBUG ("conversion successful: result = %p", result);
+        } else {
+          GST_ERROR ("prerolled but no result frame?!");
+        }
+        break;
+      }
+      case GST_MESSAGE_ERROR:{
+        gchar *dbg = NULL;
+
+        gst_message_parse_error (msg, &error, &dbg);
+        if (error) {
+          GST_ERROR ("Could not convert video frame: %s", error->message);
+          GST_DEBUG ("%s [debug: %s]", error->message, GST_STR_NULL (dbg));
+          if (err)
+            *err = error;
+          else
+            g_error_free (error);
+        }
+        g_free (dbg);
+        break;
+      }
+      default:{
+        g_return_val_if_reached (NULL);
+      }
+    }
+    gst_message_unref (msg);
+  } else {
+    GST_ERROR ("Could not convert video frame: timeout during conversion");
+    if (err)
+      *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
+          "Could not convert video frame: timeout during conversion");
+  }
+
+  gst_element_set_state (pipeline, GST_STATE_NULL);
+  gst_object_unref (bus);
+  gst_object_unref (pipeline);
+
+  return result;
+
+  /* ERRORS */
+no_encoder:
+  {
+    GST_ERROR ("could not find an encoder for provided caps");
+    if (err)
+      *err = error;
+    else
+      g_error_free (error);
+    return NULL;
+  }
+no_elements:
+  {
+    if (src)
+      gst_object_unref (src);
+    if (csp)
+      gst_object_unref (csp);
+    if (vscale)
+      gst_object_unref (vscale);
+    if (sink)
+      gst_object_unref (sink);
+    GST_ERROR ("Could not convert video frame: %s", error->message);
+    if (err)
+      *err = error;
+    else
+      g_error_free (error);
+    return NULL;
+  }
+no_pipeline:
+  {
+    GST_ERROR ("Could not convert video frame: no pipeline (unknown error)");
+    if (err)
+      *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
+          "Could not convert video frame: no pipeline (unknown error)");
+    return NULL;
+  }
+link_failed:
+  {
+    GST_ERROR ("Could not convert video frame: failed to link elements");
+    if (err)
+      *err = g_error_new (GST_CORE_ERROR, GST_CORE_ERROR_NEGOTIATION,
+          "Could not convert video frame: failed to link elements");
+    gst_object_unref (pipeline);
+    return NULL;
+  }
+}

gst-libs/gst/video/video.h

@@ -413,6 +413,9 @@ gboolean gst_video_format_convert (GstVideoFormat format, int width, int height,
 GstEvent *gst_video_event_new_still_frame (gboolean in_still);
 gboolean gst_video_event_parse_still_frame (GstEvent *event, gboolean *in_still);
 
+GstBuffer *gst_video_convert_frame(GstBuffer *buf, const GstCaps *to_caps,
+				   GstClockTime timeout, GError **error);
+
 G_END_DECLS
 
 #endif /* __GST_VIDEO_H__ */