ffplay: almost unreadable dvd subtitles due to wrong colors

[ami_stuff]

​http://www.datafilehost.com/download-76a1c6a8.html

related to:

commit cf16104ad13f6c558ea386e5fa55a67e2b378f5e
Author: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Date:   Sat Apr 30 23:00:17 2011 +0200

    Change guess_palette so its output matches the most common palette.
    
    This means it uses full brightness range and brightness
    increasing instead of decreasing with index of non-opaque
    color.
    
    Based on patch by Alexandre Colucci [alexandre elgato com]

diff --git a/libavcodec/dvdsubdec.c b/libavcodec/dvdsubdec.c
index bb3e124..6d5973c 100644
--- a/libavcodec/dvdsubdec.c
+++ b/libavcodec/dvdsubdec.c
@@ -120,6 +120,14 @@ static void guess_palette(uint32_t *rgba_palette,
                           uint8_t *alpha,
                           uint32_t subtitle_color)
 {
+    static const uint8_t level_map[4][4] = {
+        // this configuration (full range, lowest to highest) in tests
+        // seemed most common, so assume this
+        {0xff},
+        {0x00, 0xff},
+        {0x00, 0x80, 0xff},
+        {0x00, 0x55, 0xaa, 0xff},
+    };
     uint8_t color_used[16];
     int nb_opaque_colors, i, level, j, r, g, b;
 
@@ -138,18 +146,18 @@ static void guess_palette(uint32_t *rgba_palette,
     if (nb_opaque_colors == 0)
         return;
 
-    j = nb_opaque_colors;
+    j = 0;
     memset(color_used, 0, 16);
     for(i = 0; i < 4; i++) {
         if (alpha[i] != 0) {
             if (!color_used[colormap[i]])  {
-                level = (0xff * j) / nb_opaque_colors;
+                level = level_map[nb_opaque_colors][j];
                 r = (((subtitle_color >> 16) & 0xff) * level) >> 8;
                 g = (((subtitle_color >> 8) & 0xff) * level) >> 8;
                 b = (((subtitle_color >> 0) & 0xff) * level) >> 8;
                 rgba_palette[i] = b | (g << 8) | (r << 16) | ((alpha[i] * 17) << 24);
                 color_used[colormap[i]] = (i + 1);
-                j--;
+                j++;
             } else {
                 rgba_palette[i] = (rgba_palette[color_used[colormap[i]] - 1] & 0x00ffffff) |
                                     ((alpha[i] * 17) << 24);

C:\>ffmpeg -i dvdsub.vob
ffmpeg version N-36890-g67f5650 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan 16 2012 21:57:13 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib
  libavutil      51. 34.100 / 51. 34.100
  libavcodec     53. 56.105 / 53. 56.105
  libavformat    53. 30.100 / 53. 30.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 59.100 /  2. 59.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    51.  2.100 / 51.  2.100
[mpeg @ 020F2320] max_analyze_duration 5000000 reached at 5000000
Input #0, mpeg, from 'dvdsub.vob':
  Duration: 00:00:07.96, start: 1556.319267, bitrate: 5263 kb/s
    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [SAR 64:45 DA
R 16:9], 7500 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x80]: Audio: ac3, 48000 Hz, stereo, s16, 192 kb/s
    Stream #0:2[0x20]: Subtitle: dvd_subtitle
    Stream #0:3[0x22]: Subtitle: dvd_subtitle
    Stream #0:4[0x24]: Subtitle: dvd_subtitle
    Stream #0:5[0x25]: Subtitle: dvd_subtitle
    Stream #0:6[0x26]: Subtitle: dvd_subtitle
    Stream #0:7[0x28]: Subtitle: dvd_subtitle
    Stream #0:8[0x29]: Subtitle: dvd_subtitle
    Stream #0:9[0x21]: Subtitle: dvd_subtitle
    Stream #0:10[0x23]: Subtitle: dvd_subtitle
    Stream #0:11[0x27]: Subtitle: dvd_subtitle
    Stream #0:12[0x2a]: Subtitle: dvd_subtitle
At least one output file must be specified

[reimar]

To decode DVD subtitles correctly you need to provide the palette.
For DVDs the palette is in the IFO file.
FFmpeg the application does not support making use of IFO files currently.
The patch was checked against my DVD collection to generate better looking subtitles than the previous code for almost all.
It would be possible to make the code do more elaborate guessing, but it will always be guessing and there will be cases where it gets it wrong.