[FFmpeg-devel] [PATCH 1/2] Decoding of Bold Italic and Underlined styles for 3GPP timed text subtitles

[Niklesh Lalwani]

From: Niklesh <niklesh.lalwani at iitb.ac.in>

This patch is a part of my qualification task to implement support for Bold, Italic, and Underlined style records for 3GPP timed text subtitles. I am continuing Wesley's work. This patch supports decoding of no more than one style record. Patch[2/2] attempts to use dynamic arrays to support multiple style records.
Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
---
 libavcodec/movtextdec.c | 81 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 75 insertions(+), 6 deletions(-)

diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index 1c7ffea..4e463ed 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) {
+        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;
@@ -39,6 +55,16 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
             av_bprint_chars(buf, *text, 1);
             break;
         }
+
+        if (style_flags && text == style_end)
+        {
+            if (style_flags & STYLE_FLAG_BOLD)
+                av_bprintf(buf, "{\\b0}");
+            if (style_flags & STYLE_FLAG_ITALIC)
+                av_bprintf(buf, "{\\i0}");
+            if (style_flags & STYLE_FLAG_UNDERLINE)
+                av_bprintf(buf, "{\\u0}");
+        }
         text++;
     }
 
@@ -63,6 +89,9 @@ 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, tsmb_size;
+    const char *style_start, *style_end;
+    const uint8_t *tsmb;
 
     if (!ptr || avpkt->size < 2)
         return AVERROR_INVALIDDATA;
@@ -74,6 +103,7 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
      * already. If the value is non-zero, then it's technically a
      * bad packet.
      */
+
     if (avpkt->size == 2)
         return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;
 
@@ -82,7 +112,10 @@ 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);
+    //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,
@@ -91,11 +124,47 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
     ts_end   = av_rescale_q(avpkt->pts + avpkt->duration,
                             avctx->time_base,
                             (AVRational){1,100});
-
+    tsmb_size=0;
     // 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);
-    ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_end-ts_start);
+    if (text_length + 2 != avpkt->size)
+    {
+    while (text_length + 2 + tsmb_size < avpkt->size)
+    {
+        tsmb = ptr + text_length+tsmb_size; 
+        tsmb_size = AV_RB32(tsmb);  
+        tsmb += 4;
+        tsmb_type = AV_RB32(tsmb);
+        tsmb += 4;
+
+        if (tsmb_type == MKBETAG('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);
+                //fontsize=AV_RB8(tsmb);
+                //tsmb += 2;
+                // text-color-rgba
+                //tsmb += 4;
+                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)
         return ret;
-- 
1.9.1