dvdsubdec: Support palette in mkv

Matroska stores palette information as plain text in extradata.
Signed-off-by: Alexandra Khirnova <alexandra.khirnova@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/dvdsubdec.c

@@ -25,6 +25,11 @@
 
 //#define DEBUG
 
+typedef struct DVDSubContext {
+    uint32_t palette[16];
+    int      has_palette;
+} DVDSubContext;
+
 static void yuv_a_to_rgba(const uint8_t *ycbcr, const uint8_t *alpha, uint32_t *rgba, int num_values)
 {
     uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
@@ -115,7 +120,8 @@ static int decode_rle(uint8_t *bitmap, int linesize, int w, int h,
     return 0;
 }
 
-static void guess_palette(uint32_t *rgba_palette,
+static void guess_palette(DVDSubContext* ctx,
+                          uint32_t *rgba_palette,
                           uint8_t *colormap,
                           uint8_t *alpha,
                           uint32_t subtitle_color)
@@ -123,6 +129,13 @@ static void guess_palette(uint32_t *rgba_palette,
     uint8_t color_used[16] = { 0 };
     int nb_opaque_colors, i, level, j, r, g, b;
 
+    if (ctx->has_palette) {
+        for (i = 0; i < 4; i++)
+            rgba_palette[i] = (ctx->palette[colormap[i]] & 0x00ffffff)
+                              | ((alpha[i] * 17) << 24);
+        return;
+    }
+
     for(i = 0; i < 4; i++)
         rgba_palette[i] = 0;
 
@@ -159,13 +172,13 @@ static void guess_palette(uint32_t *rgba_palette,
 
 #define READ_OFFSET(a) (big_offsets ? AV_RB32(a) : AV_RB16(a))
 
-static int decode_dvd_subtitles(AVSubtitle *sub_header,
+static int decode_dvd_subtitles(DVDSubContext *ctx, AVSubtitle *sub_header,
                                 const uint8_t *buf, int buf_size)
 {
     int cmd_pos, pos, cmd, x1, y1, x2, y2, offset1, offset2, next_cmd_pos;
     int big_offsets, offset_size, is_8bit = 0;
     const uint8_t *yuv_palette = 0;
-    uint8_t colormap[4], alpha[256];
+    uint8_t colormap[4] = { 0 }, alpha[256] = { 0 };
     int date;
     int i;
     int is_menu = 0;
@@ -325,7 +338,8 @@ static int decode_dvd_subtitles(AVSubtitle *sub_header,
                     yuv_a_to_rgba(yuv_palette, alpha, (uint32_t*)sub_header->rects[0]->pict.data[1], 256);
                 } else {
                     sub_header->rects[0]->nb_colors = 4;
-                    guess_palette((uint32_t*)sub_header->rects[0]->pict.data[1],
+                    guess_palette(ctx,
+                                  (uint32_t*)sub_header->rects[0]->pict.data[1],
                                   colormap, alpha, 0xffff00);
                 }
                 sub_header->rects[0]->x = x1;
@@ -456,12 +470,13 @@ static int dvdsub_decode(AVCodecContext *avctx,
                          void *data, int *data_size,
                          AVPacket *avpkt)
 {
+    DVDSubContext *ctx = avctx->priv_data;
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     AVSubtitle *sub = data;
     int is_menu;
 
-    is_menu = decode_dvd_subtitles(sub, buf, buf_size);
+    is_menu = decode_dvd_subtitles(ctx, sub, buf, buf_size);
 
     if (is_menu < 0) {
     no_subtitle:
@@ -484,10 +499,45 @@ static int dvdsub_decode(AVCodecContext *avctx,
     return buf_size;
 }
 
+static int dvdsub_init(AVCodecContext *avctx)
+{
+    DVDSubContext *ctx = avctx->priv_data;
+    char *data, *cur;
+
+    if (!avctx->extradata || !avctx->extradata_size)
+        return 0;
+
+    data = av_malloc(avctx->extradata_size + 1);
+    if (!data)
+        return AVERROR(ENOMEM);
+    memcpy(data, avctx->extradata, avctx->extradata_size);
+    data[avctx->extradata_size] = '\0';
+    cur = data;
+
+    while (*cur) {
+        if (strncmp("palette:", cur, 8) == 0) {
+            int i;
+            char *p = cur + 8;
+            ctx->has_palette = 1;
+            for (i = 0; i < 16; i++) {
+                ctx->palette[i] = strtoul(p, &p, 16);
+                while (*p == ',' || isspace(*p))
+                    p++;
+            }
+        }
+        cur += strcspn(cur, "\n\r");
+        cur += strspn(cur, "\n\r");
+    }
+    av_free(data);
+    return 0;
+}
+
 AVCodec ff_dvdsub_decoder = {
     .name           = "dvdsub",
     .type           = AVMEDIA_TYPE_SUBTITLE,
     .id             = AV_CODEC_ID_DVD_SUBTITLE,
+    .priv_data_size = sizeof(DVDSubContext),
+    .init           = dvdsub_init,
     .decode         = dvdsub_decode,
     .long_name      = NULL_IF_CONFIG_SMALL("DVD subtitles"),
 };