mjpeg: Try to handle misformed streams.

Cameras such as D-Link's DCS-932L don't provide the first video
boundary.

modules/demux/mjpeg.c

@@ -192,10 +192,37 @@ static bool CheckMimeHeader( demux_t *p_demux, int *p_header_size )
     }
     if( strncmp( (char *)p_sys->p_peek, "--", 2 ) != 0
         && strncmp( (char *)p_sys->p_peek, "\r\n--", 4 ) != 0 )
+    {
+        /* Some broken stream may lack the first boundary */
+        if ( p_sys->psz_separator == NULL )
+        {
+            msg_Warn( p_demux, "Misformed stream. Trying to work around");
+            char *content_type = stream_ContentType( p_demux->s );
+            if ( content_type == NULL )
+                return false;
+            const char* boundary = strstr( content_type, "boundary=--" );
+            if ( boundary != NULL )
+            {
+                p_sys->psz_separator = strdup( boundary + strlen( "boundary=--" ) );
+                msg_Dbg( p_demux, "Video boundary extracted from Content-Type: %s", p_sys->psz_separator );
+                free( content_type );
+                /* Skip to HTTP header parsing as there's no boundary to extract
+                 * from the stream */
+            }
+            else
+            {
+                free( content_type );
+                return false;
+            }
+        }
+        else
         {
             *p_header_size = 0;
             return false;
         }
+    }
+    else
+    {
         i_pos = *p_sys->p_peek == '-' ? 2 : 4;
         psz_line = GetLine( p_demux, &i_pos );
         if( NULL == psz_line )
@@ -221,6 +248,7 @@ static bool CheckMimeHeader( demux_t *p_demux, int *p_header_size )
             }
             free( psz_line );
         }
+    }
 
     psz_line = GetLine( p_demux, &i_pos );
     while( psz_line && *psz_line )