commit e5e0d243546e29a24326e7aa15bd9a34a82fae37
Author: Eejya Singh <[email protected]>
Date:   Wed Jan 21 21:49:27 2015 +0530

    Adding enhanced features to WebVTT encoder

diff --git a/libavcodec/webvttenc.c b/libavcodec/webvttenc.c
index 9f67a2e..b05f363 100644
--- a/libavcodec/webvttenc.c
+++ b/libavcodec/webvttenc.c
@@ -119,6 +119,35 @@ static void webvtt_new_line_cb(void *priv, int forced)
 {
     webvtt_print(priv, "\n");
 }
+static void webvtt_color_cb(void *priv, unsigned int color, unsigned int color_id)
+{
+    WebVTTContext *s = priv;
+    if (color_id > 1)
+        return;
+
+    else
+    {
+       // webvtt_stack_push_pop(priv, 'f', (color&0xffffff) == 0xFFFFFF);
+        if ((color&0xffffff) != 0xFFFFFF)
+        {
+                /* map all levels to one level  */
+                if(!(color&0xffff00) && (color&0xff))
+                    webvtt_print(priv, "<c.red>");
+                else if(!(color&0xff00) && (color&0xff) && (color&0xff0000))
+                    webvtt_print(priv, "<c.magenta>");
+                else if(!(color&0xff00ff) && (color&0xff00))
+                    webvtt_print(priv, "<c.green>");
+                else if(!(color&0xff) && (color&0xff00) && (color&0xff0000))
+                    webvtt_print(priv, "<c.cyan>");
+                else if(!(color&0xffff) && (color&0xff0000))
+                    webvtt_print(priv, "<c.blue>");
+                else
+                	webvtt_print(priv, "<c.yellow>"); // all other colors to yellow
+        		webvtt_stack_push(s,'c');
+
+        }
+    }
+}

 static void webvtt_style_cb(void *priv, char style, int close)
 {
@@ -141,16 +170,96 @@ static void webvtt_end_cb(void *priv)
     webvtt_stack_push_pop(priv, 0, 1);
 }

+static void webvtt_alignment_cb(void *priv, int alignment)
+{
+	int	x=35,y=70;
+    char buffer[32];
+    int len;
+
+    if(alignment > 3) y=5;
+    if(alignment == 1 || alignment == 4 || alignment == 7) x= 5;
+    else if(!(alignment%3)) x=65;
+
+   	if(x == 35 && y==5) len = snprintf(buffer, sizeof(buffer),
+                                                    " line:1");
+    else if(y == 70)
+    {
+    	if(x == 5)
+        len = snprintf(buffer, sizeof(buffer),
+                                   " align:start");
+        else if (x == 65)
+        	len = snprintf(buffer, sizeof(buffer),
+                                   " align:end");
+     }
+     else
+     {
+     	if(x == 5)
+        len = snprintf(buffer, sizeof(buffer),
+                                   " line:1 align:start");
+        else len = snprintf(buffer, sizeof(buffer),
+                                   " line:1 align:end");
+      }
+
+}
+static void webvtt_move_cb(void *priv, int x1, int y1, int x2, int y2,
+                        int t1, int t2)
+{
+	WebVTTContext *s = priv;
+	char buffer[32];
+    int len;
+    if (x1 > 320 || x1 < 100 || y1 < 280)
+    {
+        int x,y,w=0,h;
+        if(x2 > x1)
+        {
+            w = x2 - x1;
+            h = y2 - y1;
+        }
+        x=35,y=70;
+        if(w < 1)
+        {
+            w=160;
+            h=96;
+        }
+        w *= 100;
+        w /= 704;
+        h *= 100;
+        h /= 480;
+
+        if(x1 < 100) x=5;
+        else if (x1 > 320) x=65;
+        if(y1 < 280) y=5;
+
+    if(w > 0) len = snprintf(buffer, sizeof(buffer),
+                          " position:%u%% line:%u%% size:%u%%", x, y, w);
+    else len = snprintf(buffer, sizeof(buffer),
+                                   " position:%u%% line:%u%%", x, y);
+
+    unsigned char *dummy;
+    unsigned room;
+
+    av_bprint_get_buffer(&s->buffer, len, &dummy, &room);
+    if (room >= len) {
+    	memmove(s->buffer.str + s->timestamp_end + len,
+                s->buffer.str + s->timestamp_end,
+                s->buffer.len - s->timestamp_end + 1);
+                memcpy(s->buffer.str + s->timestamp_end, buffer, len);
+            }
+            /* Increment even if av_bprint_get_buffer() did not return enough room:
+               the bprint structure will be treated as truncated. */
+     s->buffer.len += len;
+	}
+}
 static const ASSCodesCallbacks webvtt_callbacks = {
     .text             = webvtt_text_cb,
     .new_line         = webvtt_new_line_cb,
     .style            = webvtt_style_cb,
-    .color            = NULL,
+    .color            = webvtt_color_cb,
     .font_name        = NULL,
     .font_size        = NULL,
-    .alignment        = NULL,
+    .alignment        = webvtt_alignment_cb,
     .cancel_overrides = webvtt_cancel_overrides_cb,
-    .move             = NULL,
+    .move             = webvtt_move_cb,
     .end              = webvtt_end_cb,
 };