{"id":257,"date":"2015-08-27T15:11:00","date_gmt":"2015-08-27T15:11:00","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/video-equipment\/uncategorized\/mpeg-encodingzigzag-scanning-of-the-dct-matrix\/"},"modified":"2015-08-27T15:11:00","modified_gmt":"2015-08-27T15:11:00","slug":"mpeg-encodingzigzag-scanning-of-the-dct-matrix","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/video-equipment\/mpeg-encodingzigzag-scanning-of-the-dct-matrix\/","title":{"rendered":"MPEG encoding:Zigzag scanning of the DCT matrix"},"content":{"rendered":"<div class=\"dcdcj6a0dbc7ca1383\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '61e5902552e2353963d8d2f1bd1f4a8f',\n\t\t'format' : 'iframe',\n\t\t'height' : 250,\n\t\t'width' : 300,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/61e5902552e2353963d8d2f1bd1f4a8f\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.dcdcj6a0dbc7ca1383 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.dcdcj6a0dbc7ca1383 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.dcdcj6a0dbc7ca1383 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.dcdcj6a0dbc7ca1383 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.dcdcj6a0dbc7ca1383 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<h3 align=\"justify\">Zigzag scanning of the DCT matrix<\/h3>\n<p align=\"justify\">Before coding the quantised coefficients, the DCT matrix is reassembled into a serial stream by scanning the DCT cells in the zigzag pattern shown in Figure 4.19, starting at the top left-hand cell. The zigzag scan pattern makes it more likely that the coefficients having significant values are scanned first  <\/p>\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-NG8jp-EmBQU\/Vd8ody5y1VI\/AAAAAAAB3hE\/eRzmHHkwMBQ\/s1600-h\/MPEG-encoding-05272.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"MPEG encoding-0527\" border=\"0\" alt=\"MPEG encoding-0527\" src=\"http:\/\/lh3.googleusercontent.com\/-T_6oixAuBjs\/Vd8ojQIbjLI\/AAAAAAAB3hk\/qi1O9hXxu10\/MPEG-encoding-0527_thumb.jpg?imgmax=800\" width=\"361\" height=\"342\" \/><\/a>  <\/p>\n<p align=\"justify\">followed by low value coefficients. For the example in Figure 4.18, the scanned order is 315, 0, -6, -3, -4, -3, -1, -2, -2, 0, 0, 0, -1, 1 and -1.  <\/p>\n<p align=\"justify\">No further transmissions are necessary since the remaining coefficients are zero and thus contain no information. This is indicated by a special <i>en<\/i><i>d of block <\/i>(EOB) code, appended to the scan. Sometimes a significant coefficient may be trapped within a block of zeros, then other special codes are used to indicate a long string of zeros.  <\/p><div class=\"uhqjy6a0dbc7ca153e\" ><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-0778475562755157\"\n     crossorigin=\"anonymous\"><\/script>\n<!-- 300x600 television-and-video -->\n<ins class=\"adsbygoogle\"\n     style=\"display:inline-block;width:300px;height:600px\"\n     data-ad-client=\"ca-pub-0778475562755157\"\n     data-ad-slot=\"6549443290\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.uhqjy6a0dbc7ca153e {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.uhqjy6a0dbc7ca153e {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.uhqjy6a0dbc7ca153e {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.uhqjy6a0dbc7ca153e {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.uhqjy6a0dbc7ca153e {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"ozllk6a0dbc7ca146a\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '0c1eb4c533eaedb7b996f49a5a4983a9',\n\t\t'format' : 'iframe',\n\t\t'height' : 300,\n\t\t'width' : 160,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/0c1eb4c533eaedb7b996f49a5a4983a9\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.ozllk6a0dbc7ca146a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.ozllk6a0dbc7ca146a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.ozllk6a0dbc7ca146a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.ozllk6a0dbc7ca146a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.ozllk6a0dbc7ca146a {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\">The zigzag pattern illustrated above will optimise the number of successive zero coefficients for a progressively scanned picture frame. A different pattern (Figure 4.20) has to be used when optimising the DCT for an interlaced picture scan. This is because, in a block with an interlaced field, the DCT block contains lines from one field only, and these lines must have come from a screen area of 16 lines high. In a progressive scan, the DCT block is obtained from a screen area of eight lines high. Thus, in the case of an interlaced picture, a DCT coefficient representing a vertical spa- tial frequency is taken over a vertical dimension that is twice as large as the horizontal dimension. The probability of non-zero or significant vertical frequency coefficients is therefore twice as high as the corresponding  <\/p>\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-fNAWpZihaK4\/Vd8opPqfBcI\/AAAAAAAB3h0\/6v-9RXdLj_c\/s1600-h\/MPEG-encoding-05282.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"MPEG encoding-0528\" border=\"0\" alt=\"MPEG encoding-0528\" src=\"http:\/\/lh3.googleusercontent.com\/-pq-uy4ONdQ4\/Vd8osuqDHDI\/AAAAAAAB3iQ\/QsyB5nJlsEs\/MPEG-encoding-0528_thumb.jpg?imgmax=800\" width=\"365\" height=\"345\" \/><\/a>  <\/p>\n<p align=\"justify\">probability for horizontal frequencies. Hence, the distribution of the inter- laced coefficients is different from the distribution of the progressive coefficients. This requires a DCT scan pattern that will favour vertical frequency coefficients twice as much as horizontal frequency coefficients and hence the pattern in Figure 4.20.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Zigzag scanning of the DCT matrix Before coding the quantised coefficients, the DCT matrix is reassembled into a serial stream by scanning the DCT cells in the zigzag pattern shown in Figure 4.19, starting at the top left-hand cell. The zigzag scan pattern makes it more likely that the coefficients having significant values are scanned [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/video-equipment\/mpeg-encodingzigzag-scanning-of-the-dct-matrix\/\" class=\"more-link\" >Continue reading&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"aioseo_notices":[],"views":1087,"_links":{"self":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/257"}],"collection":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/comments?post=257"}],"version-history":[{"count":0,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/257\/revisions"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/media?parent=257"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/categories?post=257"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/tags?post=257"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}