{"id":747,"date":"2021-02-27T20:01:23","date_gmt":"2021-02-27T12:01:23","guid":{"rendered":"https:\/\/www.sunjw.cn\/?p=747"},"modified":"2021-02-27T20:01:23","modified_gmt":"2021-02-27T12:01:23","slug":"python-usage0","status":"publish","type":"post","link":"https:\/\/www.sunjw.cn\/index.php\/2021\/02\/27\/python-usage0\/","title":{"rendered":"[Python] seek\u4f7f\u7528 bytes\u8f6cint \u6d6e\u70b9\u7279\u5b9a\u4f4d\u6570"},"content":{"rendered":"<p>\u6700\u8fd1\u7528python\u5199\u4e86\u4e2a\u8ba1\u7b97pcm\u5e73\u5747RMS\u5e45\u5ea6(dBfs)\u7684\u811a\u672c\uff0c\u5176\u4e2d\u4e0d\u5c11\u5c0f\u7ec6\u8282\u5728\u6b64\u5217\u4e00\u4e0b<\/p>\n<p>1\u3001python\u6ca1\u6709\u8ddfC\u4e00\u6837\u62ff\u5230\u53c2\u6570\u4e2a\u6570\u7684argc\uff0c\u9700\u8981\u4f7f\u7528len(sys.argv)\u62ff\u5230<br \/>\n2\u3001seek\u7b2c\u4e00\u4e2a\u53c2\u6570\u4e3aoffset\uff0c\u7b2c\u4e8c\u4e2a\u4e3a\u504f\u79fb\u4f4d\u7f6e 0-file start\uff0c 1-current\uff0c2-file end<br \/>\n3\u3001python\u4e00\u4e2a\u9664\u201c\/\u201d\u7ed3\u679c\u4e3a\u6d6e\u70b9\uff0c\u5373\u4f7f\u53ef\u4ee5\u6574\u9664\uff0c\u201c\/\/\u201d\u4e3a\u53d6\u6574<br \/>\n4\u3001\u2018rb\u2019\u8bfb\u6587\u4ef6\u62ff\u5230\u7684\u6570\u636e\u4e3abytes\u7c7b\u578b\uff0c\u5982\u679c\u8981\u8f6c\u6210int\u9700\u8981int.from_bytes\u65b9\u6cd5\uff0c\u53ef\u4ee5\u8bbe\u7f6e\u5927\u5c0f\u7aef\u8ddf\u6709\u65e0\u7b26\u5408\u3002<br \/>\n5\u3001\u6d6e\u70b9\u7279\u5b9a\u4f4d\u6570\u6253\u5370<span style=\"color: #000000;\">\u00a0print(&#8220;%.2f&#8221;% num);<\/span><\/p>\n<p><span style=\"color: #ff9900;\">if len(sys.argv) != 2: #there is no ARGC<\/span><br \/>\nprint(&#8220;param must be 2&#8221;)<br \/>\nexit(0)<\/p>\n<p>with open(sys.argv[1], &#8216;rb&#8217;) as fd:<br \/>\n<span style=\"color: #ff9900;\">\u00a0 \u00a0 cnt = fd.seek(0,2)#2-seek to the end<\/span><br \/>\n<span style=\"color: #ff9900;\">\u00a0 \u00a0 cnt = cnt\/\/2 #use \/\/ here, other wise cnt is a float<\/span><br \/>\nfd.seek(0,0) #0-seek to start<br \/>\nfor i in range(cnt):<br \/>\nnum = fd.read(2)<br \/>\n<span style=\"color: #ff9900;\">\u00a0 \u00a0 \u00a0 \u00a0 num=int.from_bytes(num, byteorder=&#8221;little&#8221;, signed=&#8221;True&#8221;)# byte to int<\/span><br \/>\ntotal += (num*num)<br \/>\ndbfs=20*math.log10(math.sqrt(total\/cnt)\/32768)+3.013<br \/>\n<span style=\"color: #ff9900;\">print(&#8220;%.2f&#8221;% dbfs); #to keep 2 decimal points<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6700\u8fd1\u7528python\u5199\u4e86\u4e2a\u8ba1\u7b97pcm\u5e73\u5747RMS\u5e45\u5ea6(dBfs)\u7684\u811a\u672c\uff0c\u5176\u4e2d\u4e0d\u5c11\u5c0f\u7ec6\u8282\u5728\u6b64\u5217\u4e00\u4e0b 1\u3001python [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[12],"tags":[22,14],"_links":{"self":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/747"}],"collection":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/comments?post=747"}],"version-history":[{"count":3,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/747\/revisions"}],"predecessor-version":[{"id":750,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/posts\/747\/revisions\/750"}],"wp:attachment":[{"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/media?parent=747"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/categories?post=747"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sunjw.cn\/index.php\/wp-json\/wp\/v2\/tags?post=747"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}