/// <summary>
        /// Checks if two SubPicture object can be merged because the time gap between them is rather small
        /// and the embedded objects seem to be identical
        /// </summary>
        /// <param name="a">first SubPicture object (earlier)</param>
        /// <param name="b">2nd SubPicture object (later)</param>
        /// <returns>return true if the SubPictures can be merged</returns>
        private static bool IsPictureMergable(BluRaySupPicture a, BluRaySupPicture b)
        {
            bool eq = false;

            if (a != null && b != null)
            {
                if (a.EndTime == 0 || b.StartTime - a.EndTime < Core.GetMergePtSdiff())
                {
                    ImageObject ao = a.ObjectIdImage;
                    ImageObject bo = b.ObjectIdImage;
                    if (ao != null && bo != null)
                    {
                        if (ao.BufferSize == bo.BufferSize && ao.Width == bo.Width && ao.Height == bo.Height)
                        {
                            eq = true;
                        }
                    }
                }
            }
            return(eq);
        }
        /// <summary>
        /// parse an ODS packet which contain the image data
        /// </summary>
        /// <param name="buffer">raw byte date, starting right after segment</param>
        /// <param name="segment">object containing info about the current segment</param>
        /// <param name="pic">SubPicture object containing info about the current caption</param>
        /// <param name="msg">reference to message string</param>
        /// <returns>true if this is a valid new object (neither invalid nor a fragment)</returns>
        private static bool ParseOds(byte[] buffer, SupSegment segment, BluRaySupPicture pic, string[] msg)
        {
            ImageObjectFragment info;

            int objId  = BigEndianInt16(buffer, 0); // 16bit object_id
            int objVer = buffer[2];                 // 16bit object_id nikse - index 2 or 1???
            int objSeq = buffer[3];                 // 8bit  first_in_sequence (0x80),
            // last_in_sequence (0x40), 6bits reserved
            bool first = (objSeq & 0x80) == 0x80;
            bool last  = (objSeq & 0x40) == 0x40;

            if (pic.ImageObjects == null)
            {
                pic.ImageObjects = new List <ImageObject>();
            }
            ImageObject imgObj;

            if (objId >= pic.ImageObjects.Count)
            {
                imgObj = new ImageObject();
                pic.ImageObjects.Add(imgObj);
            }
            else
            {
                imgObj = pic.GetImageObject(objId);
            }

            if (imgObj.Fragments == null || first)
            {   // 8bit  object_version_number
                // skipped:
                //  24bit object_data_length - full RLE buffer length (including 4 bytes size info)
                int width  = BigEndianInt16(buffer, 7);     // object_width
                int height = BigEndianInt16(buffer, 9);     // object_height

                if (width <= pic.Width && height <= pic.Height)
                {
                    imgObj.Fragments     = new List <ImageObjectFragment>();
                    info                 = new ImageObjectFragment();
                    info.ImagePacketSize = segment.Size - 11; // Image packet size (image bytes)
                    info.ImageBuffer     = new byte[info.ImagePacketSize];
                    Buffer.BlockCopy(buffer, 11, info.ImageBuffer, 0, info.ImagePacketSize);
                    imgObj.Fragments.Add(info);
                    imgObj.BufferSize = info.ImagePacketSize;
                    imgObj.Height     = height;
                    imgObj.Width      = width;
                    msg[0]            = "ID: " + objId + ", update: " + objVer + ", seq: " + (first ? "first" : "") +
                                        ((first && last) ? "/" : "") + (last ? "" + "last" : "");
                    return(true);
                }
                System.Diagnostics.Debug.Print("Invalid image size - ignored");
                return(false);
            }
            // object_data_fragment
            // skipped:
            //  16bit object_id
            //  8bit  object_version_number
            //  8bit  first_in_sequence (0x80), last_in_sequence (0x40), 6bits reserved
            info = new ImageObjectFragment();
            info.ImagePacketSize = segment.Size - 4;
            info.ImageBuffer     = new byte[info.ImagePacketSize];
            Buffer.BlockCopy(buffer, 4, info.ImageBuffer, 0, info.ImagePacketSize);
            imgObj.Fragments.Add(info);
            imgObj.BufferSize += info.ImagePacketSize; // total size (may contain several packets)
            msg[0]             = "ID: " + objId + ", update: " + objVer + ", seq: " + (first ? "first" : "") + ((first && last) ? "/" : "") + (last ? "" + "last" : "");
            return(false);
        }