mpeg2enc: add disable-encode-retries property

MJPEG Tools may reencode pictures in a second pass to stick
closer to the target bitrate. This can result in slower than
real-time encoding for full HD content in certain situations,
as entire GOPs need reencoding when the reference picture is
reencoded.

See https://sourceforge.net/p/mjpeg/bugs/141/ for background

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1491>

docs/plugins/gst_plugins_cache.json

@@ -207739,6 +207739,7 @@
                 "description": "High-quality MPEG-1/2 video encoder",
                 "hierarchy": [
                     "GstMpeg2enc",
+                    "GstVideoEncoder",
                     "GstElement",
                     "GstObject",
                     "GInitiallyUnowned",
@@ -207864,6 +207865,18 @@
                         "type": "gboolean",
                         "writable": true
                     },
+                    "disable-encode-retries": {
+                        "blurb": "Prevent the encoder from reencoding pictures in a second pass. This can vastly improve performance, but potentially affect reaching bitrate targets.",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "false",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "gboolean",
+                        "writable": true
+                    },
                     "dualprime": {
                         "blurb": "Dual Prime Motion Estimation Mode for MPEG-2 I/P-frame only streams.  Quite some players do not support this.",
                         "conditionally-available": false,

ext/mpeg2enc/gstmpeg2encoder.cc

@@ -40,6 +40,14 @@
 #include "gstmpeg2enc.hh"
 #include "gstmpeg2encoder.hh"
 
+class GstOnTheFlyPass2 : public OnTheFlyPass2 {
+  public:
+    GstOnTheFlyPass2 (EncoderParams &encoder, gboolean disable_encode_retries): OnTheFlyPass2(encoder), disable_encode_retries(disable_encode_retries) {}
+    bool ReencodeRequired() const { return disable_encode_retries ? false : OnTheFlyPass2::ReencodeRequired(); }
+  private:
+    gboolean disable_encode_retries;
+};
+
 /*
  * Class init stuff.
  */
@@ -52,6 +60,7 @@ MPEG2Encoder (*options)
   caps = in_caps;
   gst_caps_ref (in_caps);
   init_done = FALSE;
+  disable_encode_retries = options->disable_encode_retries;
 }
 
 GstMpeg2Encoder::~GstMpeg2Encoder ()
@@ -89,7 +98,7 @@ gboolean GstMpeg2Encoder::setup ()
   /* encoding internals */
   quantizer = new Quantizer (parms);
   pass1ratectl = new OnTheFlyPass1 (parms);
-  pass2ratectl = new OnTheFlyPass2 (parms);
+  pass2ratectl = new GstOnTheFlyPass2 (parms, disable_encode_retries);
   /* sequencer */
   seqencoder = new SeqEncoder (parms, *reader, *quantizer,
       *writer, *pass1ratectl, *pass2ratectl);

ext/mpeg2enc/gstmpeg2encoder.hh

@@ -48,6 +48,7 @@ private:
   GstElement *element;
   GstCaps *caps;
   gboolean init_done;
+  gboolean disable_encode_retries;
 };
 
 #endif /* __GST_MPEG2ENCODER_H__ */

ext/mpeg2enc/gstmpeg2encoptions.cc

@@ -70,7 +70,8 @@ enum
   ARG_CORRECT_SVCD_HDS,
   ARG_ALTSCAN_MPEG2,
   ARG_CONSTRAINTS,
-  ARG_DUALPRIME_MPEG2
+  ARG_DUALPRIME_MPEG2,
+  ARG_DISABLE_ENCODE_RETRIES,
       /* FILL ME */
 };
 
@@ -302,6 +303,7 @@ MPEG2EncOptions ()
 
   /* set some default(s) not set in base class */
   bitrate = DEFAULT_BITRATE * 1000;
+  disable_encode_retries = FALSE;
 }
 
 /*
@@ -501,6 +503,25 @@ GstMpeg2EncOptions::initProperties (GObjectClass * klass)
           "streams.  Quite some players do not support this.",
           FALSE, (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
 
+  /**
+   * mpeg2enc:disable-encode-retries:
+   *
+   * Prevent the encoder from reencoding pictures in a second pass.
+   *
+   * This can vastly improve performance, but potentially affect reaching
+   * bitrate targets.
+   *
+   * See https://sourceforge.net/p/mjpeg/bugs/141/ for some background.
+   *
+   * Since: 1.18
+   */
+  g_object_class_install_property (klass, ARG_DISABLE_ENCODE_RETRIES,
+      g_param_spec_boolean ("disable-encode-retries", "Disable encode retries",
+          "Prevent the encoder from reencoding pictures in a second pass."
+          " This can vastly improve performance, but potentially affect reaching"
+          " bitrate targets.",
+          FALSE, (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
+
   gst_type_mark_as_plugin_api (GST_TYPE_MPEG2ENC_ASPECT, (GstPluginAPIFlags) 0);
   gst_type_mark_as_plugin_api (GST_TYPE_MPEG2ENC_FORMAT, (GstPluginAPIFlags) 0);
   gst_type_mark_as_plugin_api (GST_TYPE_MPEG2ENC_FRAMERATE, (GstPluginAPIFlags) 0);
@@ -633,6 +654,9 @@ GstMpeg2EncOptions::getProperty (guint prop_id, GValue * value)
     case ARG_DUALPRIME_MPEG2:
       g_value_set_boolean (value, hack_dualprime);
       break;
+    case ARG_DISABLE_ENCODE_RETRIES:
+      g_value_set_boolean (value, disable_encode_retries);
+      break;
     default:
       break;
   }
@@ -769,6 +793,9 @@ GstMpeg2EncOptions::setProperty (guint prop_id, const GValue * value)
     case ARG_DUALPRIME_MPEG2:
       hack_dualprime = g_value_get_boolean (value);
       break;
+    case ARG_DISABLE_ENCODE_RETRIES:
+      disable_encode_retries = g_value_get_boolean (value);
+      break;
     default:
       break;
   }

ext/mpeg2enc/gstmpeg2encoptions.hh

@@ -38,6 +38,8 @@ public:
 		    GValue       *value);
   void setProperty (guint         prop_id,
 		    const GValue *value);
+
+  gboolean disable_encode_retries;
 };
 
 #endif /* __GST_MPEG2ENCOPTIONS_H__ */