[FFmpeg-devel] [PATCH] 3GPP TS 26.245 Timed Text decoder: decode rich formatting in sample modifier boxes

[Wesley Castro]

Bold, italic, and underlined type will be converted to their equivilent ASS styles when encountered in a text style sample modifier box.

Signed-off-by: Wesley Castro <root670 at gmail.com>
---
 libavcodec/movtextdec.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 3 deletions(-)

diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index 1c7ffea..4dba1e4 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -26,9 +26,25 @@
 #include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
 
-static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
+#define STYLE_FLAG_BOLD         1
+#define STYLE_FLAG_ITALIC       2
+#define STYLE_FLAG_UNDERLINE    4
+
+static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
+                       const char *style_start, const char *style_end,
+                       const int style_flags)
 {
     while (text < text_end) {
+        if (style_flags && text == style_start)
+        {
+            if (style_flags & STYLE_FLAG_BOLD)
+                av_bprintf(buf, "{\\b1}");
+            if (style_flags & STYLE_FLAG_ITALIC)
+                av_bprintf(buf, "{\\i1}");
+            if (style_flags & STYLE_FLAG_UNDERLINE)
+                av_bprintf(buf, "{\\u1}");
+        }
+
         switch (*text) {
         case '\r':
             break;
@@ -36,9 +52,22 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
             av_bprintf(buf, "\\N");
             break;
         default:
+
             av_bprint_chars(buf, *text, 1);
+
             break;
         }
+
+        if (style_flags && text == style_end)
+        {
+            if (style_flags & STYLE_FLAG_BOLD)
+                av_bprintf(buf, "{\\b1}");
+            if (style_flags & STYLE_FLAG_ITALIC)
+                av_bprintf(buf, "{\\i1}");
+            if (style_flags & STYLE_FLAG_UNDERLINE)
+                av_bprintf(buf, "{\\u1}");
+        }
+
         text++;
     }
 
@@ -63,6 +92,9 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
     AVBPrint buf;
     const char *ptr = avpkt->data;
     const char *end;
+    int text_length, tsmb_type, style_entries, style_flags;
+    const char *style_start, *style_end;
+    const uint8_t *tsmb;
 
     if (!ptr || avpkt->size < 2)
         return AVERROR_INVALIDDATA;
@@ -82,7 +114,9 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
      * In complex cases, there are style descriptors appended to the string
      * so we can't just assume the packet size is the string size.
      */
-    end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size);
+    text_length = AV_RB16(ptr);
+
+    end = ptr + FFMIN(2 + text_length, avpkt->size);
     ptr += 2;
 
     ts_start = av_rescale_q(avpkt->pts,
@@ -94,7 +128,39 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
 
     // Note that the spec recommends lines be no longer than 2048 characters.
     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
-    text_to_ass(&buf, ptr, end);
+
+    if (text_length + 2 != avpkt->size)
+    {
+        tsmb = ptr + text_length;
+
+        //tsmb_size = AV_RB32(tsmb);
+        tsmb += 4;
+        tsmb_type = AV_RB32(tsmb);
+        tsmb += 4;
+
+        if (tsmb_type == MKTAG('s','t','y','l'))
+        {
+            style_entries = AV_RB16(tsmb);
+            tsmb += 2;
+
+            for(int i = 0; i < style_entries;i++)
+            {
+                style_start = ptr + AV_RB16(tsmb);
+                tsmb += 2;
+                style_end = ptr + AV_RB16(tsmb);
+                tsmb += 2;
+                // fontID = AV_RB16(tsmb);
+                tsmb += 2;
+                style_flags = AV_RB8(tsmb++);
+
+
+                text_to_ass(&buf, ptr, end, style_start, style_end, style_flags);
+            }
+        }
+    }
+    else
+        text_to_ass(&buf, ptr, end, NULL, NULL, 0);
+
     ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_end-ts_start);
     av_bprint_finalize(&buf, NULL);
     if (ret < 0)
-- 
1.9.1