[FFmpeg-cvslog] Fix decoding of DXSA subtitles.

[Alexandre Colucci]

ffmpeg | branch: master | Alexandre Colucci <alexandre at elgato.com> | Wed Apr 27 18:39:57 2011 +0200| [d6f910ea47255b519e0b71c33d74c409a29ab3db] | committer: Reimar Döffinger

Fix decoding of DXSA subtitles.

These have a DXSA tag and contain alpha in addition to
color values for palette.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=d6f910ea47255b519e0b71c33d74c409a29ab3db
---

 libavcodec/xsubdec.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavcodec/xsubdec.c b/libavcodec/xsubdec.c
index a577ac8..d7babe4 100644
--- a/libavcodec/xsubdec.c
+++ b/libavcodec/xsubdec.c
@@ -54,6 +54,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     int w, h, x, y, rlelen, i;
     int64_t packet_time = 0;
     GetBitContext gb;
+    int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
 
     // check that at least header fits
     if (buf_size < 27 + 7 * 2 + 4 * 3) {
@@ -100,8 +101,8 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     for (i = 0; i < sub->rects[0]->nb_colors; i++)
         ((uint32_t*)sub->rects[0]->pict.data[1])[i] = bytestream_get_be24(&buf);
     // make all except background (first entry) non-transparent
-    for (i = 1; i < sub->rects[0]->nb_colors; i++)
-        ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= 0xff000000;
+    for (i = 0; i < sub->rects[0]->nb_colors; i++)
+        ((uint32_t*)sub->rects[0]->pict.data[1])[i] |= (has_alpha ? *buf++ : (i ? 0xff : 0)) << 24;
 
     // process RLE-compressed data
     rlelen = FFMIN(rlelen, buf_end - buf);