From ef1488deebfb1a8f84ea4c0c498e50b90b75ff3d Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben@decadent.org.uk>
Date: Sat, 14 Oct 2006 02:23:02 +0000
Subject: [PATCH] Increased number of frames in menu, defined a cell covering
 each menu, and moved still time from menu PGCs to cells. This should result
 in more reliable freeze-framing.

---
 generate_dvd.cpp | 53 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/generate_dvd.cpp b/generate_dvd.cpp
index aa57775..398fdd1 100644
--- a/generate_dvd.cpp
+++ b/generate_dvd.cpp
@@ -72,6 +72,16 @@ namespace
 
 	return Glib::build_filename(dir.get_name(), base_name);
     }
+
+    // We would like to use just a single frame for the menu but this
+    // seems not to be legal or compatible.  The minimum length of a
+    // cell is 0.4 seconds but I've seen a static menu using 12 frames
+    // on a "PAL" disc so let's say 0.5 seconds rounded down.
+    const char menu_duration_string[] = "0.5";
+    unsigned menu_duration_frames(const video::frame_params & params)
+    {
+	return params.rate_numer / params.rate_denom / 2;
+    }
 }
 
 dvd_generator::dvd_generator(const video::frame_params & frame_params,
@@ -188,23 +198,31 @@ void dvd_generator::generate_menu_vob(unsigned index,
 	throw std::runtime_error("Failed to write control file for spumux");
 
     std::ostringstream command_stream;
+    unsigned frame_count(menu_duration_frames(frame_params_));
     if (encoder_ == mpeg_encoder_ffmpeg)
     {
-	command_stream
-	    << "ffmpeg"
-	    << " -f image2 -vcodec png -i "
-	    << background_name
-	    << " -target " << frame_params_.common_name <<  "-dvd"
-	    << " -vcodec mpeg2video -aspect 4:3 -an -y /dev/stdout";
+	for (unsigned i = 0; i != frame_count; ++i)
+	{
+	    std::string frame_name(background_name);
+	    frame_name.push_back('-');
+	    frame_name.push_back('0' + i / 10);
+	    frame_name.push_back('0' + i % 10);
+	    if (symlink(background_name.c_str(), frame_name.c_str()) != 0)
+		throw std::runtime_error(
+		    std::string("symlink: ").append(std::strerror(errno)));
+	}
+	command_stream <<
+	    "ffmpeg -f image2 -vcodec png -i " << background_name << "-%02d"
+	    " -target " << frame_params_.common_name <<  "-dvd"
+	    " -vcodec mpeg2video -aspect 4:3 -an -y /dev/stdout";
     }
     else
     {
 	assert(encoder_ == mpeg_encoder_mjpegtools_old
 	       || encoder_ == mpeg_encoder_mjpegtools_new);
 	command_stream
-	    << "pngtopnm "
-	    << background_name
-	    << " | ppmtoy4m -v0 -n1 -F"
+	    << "pngtopnm " << background_name
+	    << " | ppmtoy4m -v0 -n" << frame_count << " -F"
 	    << frame_params_.rate_numer << ":" << frame_params_.rate_denom
 	    << " -A" << frame_params_.pixel_ratio_width
 	    << ":" << frame_params_.pixel_ratio_height
@@ -290,7 +308,7 @@ void dvd_generator::generate(const std::string & output_dir) const
 	    // This is the first (title) menu, displayed when the
 	    // disc is first played.
 	    file <<
-		"      <pgc entry='title' pause='inf'>\n"
+		"      <pgc entry='title'>\n"
 		"        <pre>\n"
 		// Set a default target location if none is set.
 		// This covers first play and use of the "top menu"
@@ -301,7 +319,7 @@ void dvd_generator::generate(const std::string & output_dir) const
 	else
 	{
 	    file <<
-		"      <pgc pause='inf'>\n"
+		"      <pgc>\n"
 		"        <pre>\n";
 	}
 
@@ -351,7 +369,13 @@ void dvd_generator::generate(const std::string & output_dir) const
 	    "        </pre>\n"
 	    "        <vob file='"
 	     << temp_file_name(temp_dir_, "menu-%3d.mpeg", 1 + menu_index)
-	     << "'/>\n";
+	     << "'>\n"
+	    // Define a cell covering the whole menu and set a still
+	    // time at the end of that, since it seems all players
+	    // support that but some ignore a still time set on a PGC.
+	    "          <cell start='0' end='" << menu_duration_string << "'"
+	    " chapter='yes' pause='inf'/>\n"
+	    "        </vob>\n";
 
 	for (unsigned button_index = 0;
 	     button_index != this_menu.entries.size();
@@ -410,11 +434,6 @@ void dvd_generator::generate(const std::string & output_dir) const
 	}
 
 	file <<
-	    // Some DVD players don't seem to obey pause='inf' so make
-	    // them loop.
-	    "        <post>\n"
-	    "          jump cell 1;\n"
-	    "        </post>\n"
 	    "      </pgc>\n";
     }
 
-- 
2.39.2