[FFmpeg-cvslog] xsub: Support DXSA subtitles

[Alexandre Colucci]

ffmpeg | branch: release/2.4 | Alexandre Colucci <alexandre at elgato.com> | Wed Jan  7 12:18:08 2015 +0100| [3d0752d82f8eaa326cff306ae50b0186a5b4d304] | committer: Luca Barbato

xsub: Support DXSA subtitles

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

Signed-off-by: Jean-Baptiste Kempf <jb at videolan.org>
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>
(cherry picked from commit 5a1addd7c1d8ff218ed4b84f4f02fdb83980094c)
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3d0752d82f8eaa326cff306ae50b0186a5b4d304
---

 libavcodec/xsubdec.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/libavcodec/xsubdec.c b/libavcodec/xsubdec.c
index 3d85973..d01b410 100644
--- a/libavcodec/xsubdec.c
+++ b/libavcodec/xsubdec.c
@@ -56,11 +56,12 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     int w, h, x, y, i;
     int64_t packet_time = 0;
     GetBitContext gb;
+    int has_alpha = avctx->codec_tag == MKTAG('D','X','S','A');
 
     memset(sub, 0, sizeof(*sub));
 
     // check that at least header fits
-    if (buf_size < 27 + 7 * 2 + 4 * 3) {
+    if (buf_size < 27 + 7 * 2 + 4 * (3 + has_alpha)) {
         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
         return -1;
     }
@@ -107,9 +108,15 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     // read palette
     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;
+
+    if (!has_alpha) {
+        // 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;
+    } else {
+        for (i = 0; i < sub->rects[0]->nb_colors; i++)
+            ((uint32_t *)sub->rects[0]->pict.data[1])[i] |= *buf++ << 24;
+    }
 
     // process RLE-compressed data
     init_get_bits(&gb, buf, (buf_end - buf) * 8);