[FFmpeg-devel] [PATCH] Decoding of Bold-Italic-Underlined styles for 3gpp timed text

[Niklesh Lalwani]

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

This patch supports decoding of Bold, Italic, Underlined styles for 3gpp timed text. While the code can be improved upon to make it more clean and well structured, this works for now, even for multiple style records. Suggestions awaited.
Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
---
 libavcodec/movtextdec.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 82 insertions(+), 4 deletions(-)

diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index 1c7ffea..a4aa7cb 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -25,10 +25,28 @@
 #include "libavutil/common.h"
 #include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
+#include "libavutil/mem.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, const int style_entries)
 {
     while (text < text_end) {
+        for (int i=0; i<style_entries; i++) {
+            if (*style_flags[i] && text == style_start[i]) {
+                if (*style_flags[i] & STYLE_FLAG_BOLD)
+                    av_bprintf(buf, "{\\b1}");
+                if (*style_flags[i] & STYLE_FLAG_ITALIC)
+                    av_bprintf(buf, "{\\i1}");
+                if (*style_flags[i] & STYLE_FLAG_UNDERLINE)
+                    av_bprintf(buf, "{\\u1}");
+            }
+        }
+
         switch (*text) {
         case '\r':
             break;
@@ -39,6 +57,17 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end)
             av_bprint_chars(buf, *text, 1);
             break;
         }
+
+        for (int i=0; i<style_entries; i++) {
+            if (*style_flags[i] && text == style_end[i]) {
+                if (*style_flags[i] & STYLE_FLAG_BOLD)
+                    av_bprintf(buf, "{\\b0}");
+                if (*style_flags[i] & STYLE_FLAG_ITALIC)
+                    av_bprintf(buf, "{\\i0}");
+                if (*style_flags[i] & STYLE_FLAG_UNDERLINE)
+                    av_bprintf(buf, "{\\u0}");
+            }
+        }
         text++;
     }
 
@@ -63,6 +92,13 @@ 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, tsmb_size;
+    char **style_start={0,}; 
+    char **style_end={0,};
+    int **style_flags={0,};
+    const uint8_t *tsmb;
+    int index,i, flag=0;;
+    char *ptr_temp;
 
     if (!ptr || avpkt->size < 2)
         return AVERROR_INVALIDDATA;
@@ -82,7 +118,8 @@ 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,
@@ -92,10 +129,51 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
                             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(i = 0; i < style_entries;i++) {
+                    ptr_temp= ptr + AV_RB16(tsmb);
+                    index=i;
+                    av_dynarray_add(&style_start, &index, ptr_temp);
+                    tsmb += 2;
+                    ptr_temp= ptr+ AV_RB16(tsmb);
+                    index=i;
+                    av_dynarray_add(&style_end, &index, ptr_temp);
+                    tsmb += 2;
+                    // fontID = AV_RB16(tsmb);
+                    tsmb += 2;
+                    flag=AV_RB8(tsmb);
+                    index=i;
+                    av_dynarray_add(&style_flags, &index, &flag);
+                    //fontsize=AV_RB8(tsmb);
+                    tsmb += 2;
+                    // text-color-rgba
+                    tsmb += 4;
+                }
+                text_to_ass(&buf, ptr, end, style_start, style_end, style_flags,style_entries);
+                av_freep(&style_start);
+                av_freep(&style_end);
+                av_freep(&style_flags);
+            }
+        }
+    }
+    else
+        text_to_ass(&buf, ptr, end, NULL, NULL, 0, 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