{"id":331,"date":"2006-09-13T18:55:37","date_gmt":"2006-09-14T01:55:37","guid":{"rendered":"http:\/\/multimedia.cx\/eggs\/my-app-a-day\/"},"modified":"2006-09-13T18:55:37","modified_gmt":"2006-09-14T01:55:37","slug":"my-app-a-day","status":"publish","type":"post","link":"https:\/\/multimedia.cx\/eggs\/my-app-a-day\/","title":{"rendered":"My App A Day"},"content":{"rendered":"<p><a href=\"http:\/\/www.anappaday.com\/\">This ambitious software developer<\/a>, the Software Jedi, wants to write an app a day for a month and he is soliciting suggestions. <\/p>\n<p><center><br \/>\n<img decoding=\"async\" src=\"\/eggs\/images\/Nuvola_apps_ktip.png\" alt=\"bright idea\" \/><br \/>\n<\/center><\/p>\n<p>Here is one idea that I dreamed up just the other day as I was plodding through the hex dump of yet another freshly discovered, FourCC-chunked multimedia file format. This is the proposal&#8211; maybe he will find it interesting enough to write up in C#, maybe I will have to do it instead, or maybe someone else will beat me to it:<\/p>\n<p>A lot of multimedia files use what I like to call the &#8220;chunked-FourCC&#8221; format:<\/p>\n<pre>\r\n  chunk 0\r\n  chunk 1\r\n   ..\r\n  chunk n\r\n<\/pre>\n<p>Chunks are formatted as:<\/p>\n<pre>\r\n  preamble\r\n  payload\r\n<\/pre>\n<p>The preamble invariably consists of:<\/p>\n<pre>\r\n  chunk identifier-- usually 4 ASCII chars (FourCC)\r\n  length\r\n<\/pre>\n<p>When I stumble on a new chunked-FourCC-type file format, I want to know all of the possible chunk types. I want a simple tool that could walk through all the chunks in the file and print the various types.<\/p>\n<p>At issue is the preamble format&#8211; sometimes the FourCC is first, sometimes the length is first; sometimes the length is big endian, sometimes it&#8217;s little endian; sometimes there is an extra &#8220;flags&#8221; component to the preamble; sometimes the length includes the preamble chunk, sometimes it doesn&#8217;t.<\/p>\n<p>So I am thinking of a utility where I can specify all of these parameters from the command line and the tool would print info about the chunks based on those instructions. A good starting point would be any Apple QuickTime (.mov) file. The chunk (&#8220;atom&#8221;) format is (and all multi-byte numbers are big endian):<\/p>\n<pre>\r\n  bytes 0-3    atom size (including 8-byte size and type preamble)\r\n  bytes 4-7    atom type (ASCII chars, usually)\r\n  bytes 8..    data\r\n<\/pre>\n<p>There is also a special case for large atoms:<\/p>\n<pre>\r\n  bytes 0-3    always 0x00000001\r\n  bytes 4-7    atom type\r\n  bytes 8-15   atom size (including 16-byte size and type preamble)\r\n  bytes 16..n  data\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>This ambitious software developer, the Software Jedi, wants to write an app a day for a month and he is soliciting suggestions. Here is one idea that I dreamed up just the other day as I was plodding through the hex dump of yet another freshly discovered, FourCC-chunked multimedia file format. This is the proposal&#8211; [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-331","post","type-post","status-publish","format-standard","hentry","category-open-source-multimedia"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/posts\/331","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/comments?post=331"}],"version-history":[{"count":0,"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/posts\/331\/revisions"}],"wp:attachment":[{"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/media?parent=331"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/categories?post=331"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/multimedia.cx\/eggs\/wp-json\/wp\/v2\/tags?post=331"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}