<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Austin,<div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Sep 3, 2017, at 9:08 AM, Austin Einter <<a href="mailto:austin.einter@gmail.com" class="">austin.einter@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">First of all a BIG THANKS to Matroska, for providing a open source media file container. <div class=""><br class=""></div><div class="">I have a requirement, where I need to parse a matroska file. Initial few bytes of file is given as below.</div><div class=""><br class=""></div><div class=""><div class="">0x1a 0x45 0xdf 0xa3 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x23 0x42 0x86 0x81 0x01</div><div class="">0x42 0xf7 0x81 0x01 0x42 0xf2 0x81 0x04 0x42 0xf3 0x81 0x08 0x42 0x82 0x88 0x6d</div><div class="">0x61 0x74 0x72 0x6f 0x73 0x6b 0x61 0x42 0x87 0x81 0x04 0x42 0x85 0x81 0x02 0x18</div><div class="">0x53 0x80 0x67 0x01 0x00 0x00 0x00 0x00 0x33 0xdb 0x10 <b class="">0x11 0x4d 0x9b 0x74</b> 0x40</div><div class="">0x42 0xbf 0x84 0x11 0xac 0x83 0x8a 0x4d 0xbb 0x8b 0x53 0xab 0x84 0x15 0x49 0xa9</div><div class="">0x66 0x53 0xac 0x81 0xe5 0x4d 0xbb 0x8c 0x53 0xab 0x84 0x16 0x54 0xae 0x6b 0x53</div><div class="">0xac 0x82 0x01 0x56 0x4d 0xbb 0x8c 0x53 0xab 0x84 0x12 0x54 0xc3 0x67 0x53 0xac</div><div class="">0x82 0x11 0x5c 0x4d 0xbb 0x8d 0x53 0xab 0x84 0x1c 0x53 0xbb 0x6b 0x53 0xac 0x83</div><div class="">0x33 0xd9 0x1c 0xec 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x94 0x00 0x00 0x00 0x00</div><div class="">0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00</div><div class="">0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00</div></div><div class=""><br class=""></div><div class="">I am trying to parse this file. I have parsed first 59 bytes successfully. Now I am at 60th byte. From 6th byte bytes are 0x11 0x4d 0x9b 0x74, so it means seekhead is starting. </div><div class=""><br class=""></div><div class="">I used mkvinfo to view parsed data. As per mkvinfo as shown below, seekhead starts at 59 which is fine. </div><div class=""><br class=""></div><div class=""> <span id="cid:ii_15e47d9c56acaf21"><image.png></span></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Looks the first seek entry starts at 71. Now from 59th to 71st position what is there. This part I am not able to understand.</div><div class=""><br class=""></div><div class="">Can somebody please help me to understand this part.</div></div></div></blockquote></div><div class=""><br class=""></div>As noted the SeekHead element starts at position 59. The first Child Element of SeekHead is then a CRC-32 element, which is:<br class=""></div><div class=""><blockquote type="cite" class=""><div dir="ltr" class=""><div class=""><div class="">0xbf 0x84 0x11 0xac 0x83 0x8a</div></div></div></blockquote><br class=""></div><div class="">Element ID: 0xbf</div><div class="">Element Data Size: 0x84</div><div class="">Element Value: 0x11 0xac 0x83 0x8a</div><div class=""><br class=""></div><div class="">After the CRC-32 Element is the first Seek Element.</div><div class=""><br class=""></div><div class="">More info about the CRC-32 element is in the EBML specification, see <a href="https://tools.ietf.org/html/draft-ietf-cellar-ebml" class="">https://tools.ietf.org/html/draft-ietf-cellar-ebml</a>.</div><div class="">Dave Rice</div></body></html>