{"id":373,"date":"2022-01-31T18:04:42","date_gmt":"2022-01-31T10:04:42","guid":{"rendered":"http:\/\/192.168.0.122:8088\/?p=373"},"modified":"2022-06-11T03:16:05","modified_gmt":"2022-06-10T19:16:05","slug":"ffmpeg%e5%91%bd%e4%bb%a4%e5%88%86%e6%9e%90-r","status":"publish","type":"post","link":"https:\/\/www.xianwaizhiyin.net\/?p=373","title":{"rendered":"ffmpeg\u547d\u4ee4\u5206\u6790-r"},"content":{"rendered":"\n

\u672c\u7cfb\u5217 \u4ee5 ffmpeg4.2 \u6e90\u7801\u4e3a\u51c6\uff0c\u4e0b\u8f7d\u5730\u5740\uff1a\u94fe\u63a5\uff1a\u767e\u5ea6\u7f51\u76d8<\/a> \u63d0\u53d6\u7801\uff1ag3k8<\/p>\n\n\n\n

\u4e4b\u524d\u7684\u6587\u7ae0\u5206\u6790 FFMpeg \u5de5\u7a0b\u7684 do_video_out() \u51fd\u6570\u7684\u65f6\u5019\uff0c\u5efa\u8bae\u4e0d\u5173\u6ce8 delta0<\/code>\uff0cdelta<\/code>\uff0cnb0_frames<\/code>\uff0cnb_frames<\/code> \u7b49\u53d8\u91cf\u3002<\/p>\n\n\n\n

\u56e0\u4e3a\u5728\u4e4b\u524d\u7684\u547d\u4ee4\u6ca1\u6709\u7528\u5e27\u7387\u53d8\u6362\u53c2\u6570\uff0c-r \u3002\u6240\u4ee5\u4e0a\u9762\u8fd9\u4e9b\u53d8\u91cf\u8d4b\u503c\uff0c\u6709\u8ddf\u6ca1\u6709\u662f\u4e00\u6837\u7684\u3002<\/p>\n\n\n\n

\u73b0\u5728\u6765\u8865\u4e00\u4e0b\u4e4b\u524d\u7f3a\u5931\u7684\u5185\u5bb9\u3002\u547d\u4ee4\u884c\u6307\u5b9a -r \u4e4b\u540e\uff0cdelta0<\/code>\uff0cdelta<\/code>\uff0cnb0_frames<\/code>\uff0cnb_frames<\/code> \u7684\u53d8\u5316\u3002<\/p>\n\n\n\n

\u672c\u6587\u7ae0\u4e3b\u8981\u8bb2\u89e3 FFMpeg \u91cc\u9762\u662f\u5982\u4f55\u5b9e\u73b0\u5e27\u7387\u53d8\u6362\u7684\uff0c\u4f8b\u5982 24fps \u662f\u5982\u4f55\u8f6c\u6210 8fps\u7684\uff0c\u7f29\u5c0f\u4e863\u500d\u7684\u5e27\u7387\u3002<\/p>\n\n\n\n

.\/ffmpeg -i a.mp4 -r 8 output.flv<\/code> \u672c\u6587\u4ee5\u6b64\u547d\u4ee4\u8bb2\u89e3\uff0c\u539f\u59cb\u89c6\u9891\u662f24fps\uff0c\u8f6c\u6210 8fps\u3002<\/p>\n\n\n\n

a.mp4 \u4e0b\u8f7d\u94fe\u63a5\uff1a\u767e\u5ea6\u7f51\u76d8<\/a> \uff0c\u63d0\u53d6\u7801\uff1anl0s<\/p>\n\n\n\n

\n\n\n\n

\u5982\u679c\u6ca1\u6307\u5b9a -r \uff0c\u5c31\u4f1a\u4ece buffersink \u83b7\u53d6\u8f93\u51fa\u7684\u5e27\u7387\uff0c\u5e27\u7387\u8ddf\u8f93\u5165\u6587\u4ef6\u5e27\u7387\u4e00\u6837\uff0c\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\u5982\u679c\u547d\u4ee4\u884c\u6307\u5b9a\u4e86 -r \uff0c\u5c31\u4f1a\u7528\u547d\u4ee4\u884c\u53c2\u6570\u8d4b\u503c \u7ed9 ost->frame_rate<\/code>\u3002\uff0c\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\n\n\n\n

\u4e0a\u9762\u662f \u547d\u4ee4\u884c\u53c2\u6570 -r \u8d4b\u503c\u7ed9 ost->frame_rate<\/code>\u3002\u7136\u540e ost->frame_rate<\/code> \u4f1a\u4f5c\u4e3a\u65f6\u95f4\u57fa\u8d4b\u503c\u7ed9 \u7f16\u7801\u5668\u7684time_base\uff0c\u89c1\u4e0b\u56fe\u4ee3\u7801\uff1a<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\n\n\n\n

google_ads_content<\/p>\n\n\n\n

\n\n\n\n

\u6240\u4ee5\uff0c\u7efc\u4e0a\u6240\u8ff0\uff0c-r \u6700\u540e\u4e3b\u8981\u5f71\u54cd\u7684\u662f \u7f16\u7801\u5668\u7684time_base\uff0c\u90a3\u7f16\u7801\u5668\u7684time_base\u662f\u600e\u4e48\u5f71\u54cd\u5e27\u7387\u53d8\u6362\u7684\u5462\uff1f\u8bf7\u770b\u4e0b\u9762\u3002<\/p>\n\n\n\n

\u5728\u8bb2\u4e4b\u524d\uff0c\u9700\u8981\u666e\u53ca\u4e00\u4e2a\u77e5\u8bc6\u70b9\uff0c\u8bf7\u770b\u4e0b\u9762\u4ee3\u7801<\/p>\n\n\n\n

int a = av_rescale_q(1,  (AVRational){1, 24}, (AVRational){1, 12});\nint b = av_rescale_q(2,  (AVRational){1, 24}, (AVRational){1, 12});<\/code><\/pre>\n\n\n\n
\u8fd9\u91cc a \u8ddf b \u90fd\u662f1\uff0ca\u4e0d\u4f1a\u662f0.5\u3002av_rescale_q()<\/code> \u8fd4\u56de\u7684\u6574\u6570\uff0c\u6240\u4ee5\u7cbe\u5ea6\u4e22\u5931\u4e86\u3002\u8fd9\u4e5f\u662f\u4e3a\u4ec0\u4e48 reap_filtes()<\/code> \u5185\u90e8\u4f1a\u641e\u4e00\u4e2a float_pts \u51fa\u6765\uff0c\u8fd9\u4e2afloat_pts \u662f\u6709\u7cbe\u5ea6\u7684\u3002\u8bf7\u770b\u4e0b\u56fe\uff0c\u7f16\u7801\u5668\u7684time_base \u7684\u5f71\u54cd\u5c31\u5728\u8fd9\u91cc\u3002<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\u53ef\u4ee5\u770b\u5230\uff0c\u4e0a\u56fe\u4ee3\u7801\u628a\u539f\u59cb\u89c6\u9891\u5e27 \u7684pts \u7684\u65f6\u95f4\u57fa\u8f6c\u6210 \u7f16\u7801\u5668\u7684time_base\u4e86\u3002\u8fd9\u91cc\u662f\u4e00\u4e2a\u4ec0\u4e48\u6982\u5ff5\u5462\u3002<\/p>\n\n\n\n
\u5047\u5982\u539f\u59cb\u89c6\u9891\u5e27\u7387\u662f\u6bcf\u79d224\u5e27\uff0c\u4ed6AVFrame\u7684pts\u7684\u65f6\u95f4\u57fa\u4e5f\u662f {1,24}\u3002\u90a3\u8fd9\u65f6\u5019\u8fd9\u4e2a filtered_frame->pts<\/code> \u80af\u5b9a\u662f1,2,3,4 \u8fd9\u6837\u9012\u589e\u4e0b\u53bb\u7684\u3002<\/p>\n\n\n\n
\u628a filtered_frame->pts<\/code> \u8f6c\u6210\u7f16\u7801\u5668\u65f6\u95f4\u57fa {1,8} \u4f1a\u600e\u6837\uff1f<\/p>\n\n\n\n
\u64ad\u653e\u65f6\u95f4pts\u4e0d\u53d8\uff0c1\/24 = 0.041s \uff0c\u7b2c\u4e00\u5e27\u5728 0.041s \u64ad\u653e\u3002\u7136\u540e x\/8 = 0.041\uff0c\u8fd9\u4e2ax\u7b49\u4e8e\u591a\u5c11\u5462\uff1fx = 0.333\u3002<\/p>\n\n\n\n
\u4e5f\u5c31\u662f\u8bf4\uff0c\u7b2c\u4e8c\u5e27\u7684 filtered_frame->pts<\/code> \u539f\u672c\u662f 1\uff0c\u65f6\u95f4\u57fa\u4ece {1,24} \u8f6c\u6210 {1,8} \u4e4b\u540e\uff0cpts \u4ece1 \u53d8\u6210\u4e86 0.333\u3002<\/p>\n\n\n\n
\u7c7b\u63a8\uff0c\u7b2c\u4e09\u5e27pts\u53d8\u6210\u4e86 0.666\uff0c\u7b2c\u56db\u79cd\u53d8\u62100.999\u3002<\/p>\n\n\n\n
\u7136\u540e\uff0c\u8fd9\u4e9b\u8ddf\u5e27\u7387\u53d8\u6362\u6709\u4ec0\u4e48\u5173\u7cfb\uff1f\u8bf7\u7ee7\u7eed\u770b\u4e0b\u9762\u5206\u6790\u3002<\/p>\n\n\n\n
\u56e0\u4e3a\u5e27\u7387\u53d8\u6362\u6d89\u53ca\u5230\u597d\u51e0\u4e2a\u573a\u666f\uff0c\u8fd9\u91cc\u53ea\u4ecb\u7ecd format_video_sync = VSYNC_VFR<\/code> \u7684\u573a\u666f<\/strong><\/p>\n\n\n\n
\u63a5\u7740\u5206\u6790\uff0c\u867d\u7136\u4e0a\u9762\u8bf4\u5230\uff0c\u539f\u59cbpts\u8f6c\u6362\u4e4b\u540e\u53d8\u6210\u4e86 0.33,0.66 \u4e4b\u7c7b\u7684\u5c0f\u6570\u3002\u4f46\u662f\u5bf9\u4e8e\u8f93\u5165\u6587\u4ef6\uff0c\u5bf9\u4e8e\u7f16\u7801\u5668\u6765\u8bf4\uff0c\u7f16\u7801\u5668\u7684\u5e27\u7387\u662f 8fps\uff0c{1,8}\uff0c\u4f20\u9012\u7ed9\u7f16\u7801\u5668\u7684frame\u7684pts\uff0c\u80af\u5b9a\u4e5f\u5fc5\u987b\u662f 1,2,3,4 \u8fd9\u6837\u7684\u6574\u6570\u9012\u589e\u7684\u3002\u8fd9\u91cc\u5b9e\u73b0\u8fd9\u4e2a\u529f\u80fd\u7684\u662f ost->sync_opts<\/code> \u53d8\u91cf\u3002<\/p>\n\n\n\n
\u8981\u597d\u597d\u5206\u6790\u4e00\u4e0b ost->sync_opts<\/code> \u8fd9\u4e2a\u53d8\u91cf\uff0c\u8fd9\u4e2a\u53d8\u91cf\u7684\u521d\u59cb\u503c\u662f 0\uff0c\u6bcf\u8f93\u5165\u4e00\u4e2aframe\u7ed9\u7f16\u7801\u5668\uff0cost->sync_opts<\/code> \u5c31\u4f1a+1\u3002<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\u5982\u4e0a\u56fe\u6240\u793a\uff0cdo_video_out() \u7684 in_picture \u5e27\u7684pts\u4f1a\u88ab ost->sync_opts<\/code> \u66ff\u6362\uff0c\u8fbe\u5230 \u8f93\u5165\u7ed9\u7f16\u7801\u5668\u7684frame pts \u90fd\u662f 1,2,3,\u9012\u589e\u7684\u76ee\u7684\u3002<\/p>\n\n\n\n
\u63a5\u4e0b\u6765\u7ee7\u7eed\u8bb2\uff0c\u4e0a\u9762\u90a3\u4e9b0.33\uff0c0.66\u5c0f\u6570\u662f\u7528\u6765\u5e72\u561b\u7684\uff1f\u5176\u5b9e\u8fd9\u4e9b\u5c0f\u6570\u5c31\u662f\u7528\u6765\u4e22\u5e27\uff0c\u5b9e\u73b0\u5e27\u7387\u7f29\u5c0f\u7684\u529f\u80fd\uff0c\u6216\u8005\u91cd\u590d\u4e0a\u4e00\u5e27\uff0c\u5b9e\u73b0\u5e27\u7387\u53d8\u5927\u529f\u80fd\u3002<\/p>\n\n\n\n
\u5982\u4e0b\u56fe\u6240\u793a\uff0cnb0_frames \u8fd9\u4e2a\u53d8\u91cf\u4e0d\u7528\u7ba1\uff0c\u5728format_video_sync = VSYNC_VFR<\/code> \u7684\u573a\u666f \u4e0b\uff0cnb0_frames \u603b\u662f0\u3002<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\u7b2c\u4e00\u5e27\u5168\u662f0\uff0c\u770b\u4e0d\u51fa\u4e0a\u9762\u7684\u903b\u8f91\uff0c\u76f4\u63a5\u4ece\u7b2c\u4e8c\u5e27\u5f00\u59cb\u5206\u6790\u3002\u7b2c\u4e8c\u5e27 do_video_out() \u4f20\u9012\u7684 sync_ipts \u662f0.333\u3002\u4f46\u662f\u6b64\u65f6 sync_opts \u662f 1\u3002<\/p>\n\n\n\n
\u5927\u5bb6\u53ef\u4ee5\u4ed4\u7ec6\u7422\u78e8\u4e00\u4e0b\u90a3\u53e5\u82f1\u6587\u6ce8\u91ca\uff0c\u8001\u5916\u5199\u6ce8\u91ca\u90fd\u6bd4\u8f83\u7b80\u6d01\u3002<\/p>\n\n\n\n
delta0 is the \"drift\" between the input frame (next_picture) and where it would fall in the output.<\/pre>\n\n\n\n
delta0 = 0.333 - 1 = -0.666\uff0cdelta0 \u4ee3\u8868\u5f53\u524d\u8f93\u5165\u5e27\u4e0e\u8f93\u51fa\u7ed9\u7f16\u7801\u5668\u7684\u65f6\u95f4\u5dee\u8ddd\uff0c\u5728\u7b2c\u4e8c\u5e27\u7684\u65f6\u5019\uff0c\u65f6\u95f4\u5dee\u662f 0.666\u3002\u89e3\u6790\u5230\u8fd9\u91cc\uff0c\u5e94\u8be5\u6709\u70b9\u7709\u76ee\uff0c\u7f29\u5c0f\u5e27\u7387\uff0c\u80af\u5b9a\u8981\u6839\u636e\u65f6\u95f4\u5dee\u8ddd\u6765\u4e22\u5f03\u67d0\u4e9b\u5e27\u3002<\/p>\n\n\n\n
\u8bf4\u5b9e\u8bdd\uff0c\u4ed6\u8fd9\u4e2a\u7b97\u6cd5\u6709\u70b9\u590d\u6742\uff0c\u6211\u4e5f\u4e0d\u592a\u660e\u767d\u4ed6\u4e3a\u4ec0\u4e48\u4e0d sync_ipts < sync_opts \u5c31\u76f4\u63a5\u4e22\u5f03\uff0c\u8fd9\u6837\u4e0d\u662f\u66f4\u7b80\u5355\uff1f\u8fd9\u4e2a\u95ee\u9898\u5148\u4e0d\u7ea0\u7ed3\uff0c\u63a5\u7740\u5206\u6790ffmpeg \u662f\u5982\u4f55\u7528delta0 \uff0cdelta \u5b9e\u73b0\u4e22\u5e27\u7684\u3002\u8865\u5145\uff1a\u76f4\u63a5 sync_ipts < sync_opts \u4e0d\u884c\uff0c\u4f1a\u51fa\u9519\u3002<\/p>\n\n\n\n
\u8fd9\u4e2a\u7b97\u6cd5\u6d89\u53ca\u5230\u4e0d\u540c\u523b\u5ea6\u8868\u7684\u8f6c\u6362\uff0c\u7528\u4e24\u4e2a\u523b\u5ea6\u8868\u6765\u89e3\u91ca\u8fd9\u4e2a\u7b97\u6cd5\u4f1a\u66f4\u660e\u767d\u3002<\/p>\n\n\n\n
delta0 = sync_ipts - ost->sync_opts; 
delta  = sync_ipts - ost->sync_opts + duration;<\/pre>\n\n\n\n
\u53ef\u4ee5\u770b\u5230\uff0c\u56e0\u4e3a ost->sync_opts<\/code> \u6bcf\u6b21\u90fd\u4f1a +1 \u5730\u9012\u589e\uff0c\u800c sync_ipts \u6bcf\u6b21\u53ea\u80fd +0.3 \u9012\u589e\u3002\u6240\u4ee5delta\u4f1a\u8d1f\u5f97\u8d8a\u6765\u8d8a\u5927\uff0cduration\u662f\u56fa\u5b9a\u662f 0.33\u3002\u6240\u4ee5delta\u4e5f\u4f1a\u8d1f\u5f97\u8d8a\u6765\u8d8a\u5927\uff0c\u7136\u540e delta <= -0.6 \u5c31\u4f1a\u628a nb_frames \u7f6e\u4e3a 0 \uff0c\u5bfc\u81f4\u540e\u9762\u7684for\u5faa\u73af\u6ca1\u6267\u884c\uff0c\u5b9e\u73b0\u4e22\u5e27\u3002\u81f3\u4e8e\u4e3a\u4ec0\u4e48\u662f0.6\u6211\u4e5f\u4e0d\u77e5\u9053\u3002\u5b9e\u5728\u6ca1\u60f3\u597d\u600e\u4e48\u8868\u8fbe\u4ed6\u8fd9\u4e2a\u7b97\u6cd5\u903b\u8f91\uff0c\u53cd\u6b63\u4ee3\u7801\u903b\u8f91\u5b83\u5c31\u662f\u8fd9\u4e48\u8dd1\u7684\uff0cdelta\u8d8a\u6765\u8d8a\u5927\uff0c\u5c31\u4e22\u5e27\u3002\u4e22\u5e27\u540e\uff0cost->sync_opts \u4e0d\u4f1a+1\uff0csync_ipts \u5c31\u4f1a\u6162\u6162\u8d76\u4e0a sync_opts<\/p>\n\n\n\n
case VSYNC_VFR:\n    if (delta <= -0.6){\n        \/\/\u4e22\u5f03 frame\n        nb_frames = 0;\n    }\n    else if (delta > 0.6)\n        ost->sync_opts = lrint(sync_ipts);\n    break;<\/code><\/pre>\n\n\n\n
\u5b9e\u9645\u4e22\u5e27\u60c5\u51b5\u5982\u4e0b\u3002<\/p>\n\n\n\n
0 0.33 0.66(x) 1(x) 1.33 1.66(x) 2(x) 2.33 2.66(x) 3(x)<\/p>\n\n\n\n
\u53ea\u6709 .33 \u540e\u7f00\u7684\u5e27\u624d\u4f1a\u4fdd\u7559\uff0c\u786e\u5b9e\u662f\u7f29\u5c0f\u4e863\u500d\u5e27\u7387\u3002<\/p>\n\n\n\n
\u5b9e\u9645\u4e0a\uff0c\u4ed6\u8fd9\u4e2a\u7b97\u6cd5\u5e94\u8be5\u662f\u4e00\u4e2a\u6570\u5b66\u516c\u5f0f\uff0csync_ipts + duration + 60% \u523b\u5ea6 > sync_opts\uff0c\u5982\u679c\u5927\u4e8e sync_opts\u5c31\u53ef\u4ee5 \u8f93\u51fa\u7ed9\u89e3\u7801\u5668\uff0c\u5c0f\u4e8e\u5c31\u4e22\u5f03\u3002\u8fd9\u91cc\u7684\u523b\u5ea6\u662f1\uff0c\u6240\u4ee560%\u523b\u5ea6\u662f0.6\u3002sync_ipts + duration \u662f\u56e0\u4e3a\u53ea\u8981\u8fd9\u4e2aframe\u7684\u533a\u95f4\u8de8\u8fc7 sync_opts \u523b\u5ea6\uff0c\u54ea\u6015\u8de8\u8fc7\u4e00\u70b9\u70b9\uff0c\u90fd\u53ef\u4ee5\u8f93\u51fa\u3002<\/p>\n\n\n\n
\n\n\n\n
\u5982\u679c\u4e0d\u6539\u53d8\u5e27\u7387\uff0csync_opts \u8ddf sync_ipts \u662f\u540c\u6b65+1\u7684\uff0cduration\u4e5f\u662f1\uff0c\u7136\u540e delta0 \u4e00\u76f4\u662f\u4e00\u4e2a\u975e\u5e38\u5c0f\u7684\u63a5\u8fd10\u7684\u6570\u5b57\uff0cdelta \u4e00\u76f4\u662f\u63a5\u8fd11\u7684\u6570\u5b57\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u4e0d\u6539\u53d8\u5e27\u7387\uff0cdelta0 \u8ddfdelta \u8fd9\u4e9b\u53d8\u91cf\u662f\u6ca1\u6709\u4f5c\u7528\u7684\u3002<\/p>\n\n\n\n
\n\n\n\n
\u63a5\u4e0b\u6765\u7ee7\u7eed\u5206\u6790 \u5e27\u7387\u653e\u5927\u7b97\u6cd5\u662f\u5982\u4f55\u5b9e\u73b0\u7684\u3002<\/p>\n\n\n\n
\u628a \u5e27\u7387 {1,24} \u8f6c\u6210 {1,48}\uff0c\u5b9e\u9645\u4e0a\u5c31\u662f\u628a pts \u4e58\u4ee5 2 \u3002<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\u6ce8\u610f\uff0c\u6709\u4e9bMP4 \u662f VSYNC_CFR\uff0c\u6709\u4e9b\u662f VSYNC_VFR\u3002<\/p>\n\n\n\n
CFR \u7684\u5e27\u7387\u7ffb\u500d\uff0c\u4f1a\u63d2\u5165\u65b0\u5e27\uff0c\u6587\u4ef6\u5927\u5c0f\u4e5f\u4f1a\u7ffb\u500d\u3002<\/p>\n\n\n\n
VFR \u7684\u5e27\u7387\u7ffb\u500d\uff0c\u4e0d\u4f1a\u63d2\u5165\u65b0\u5e27\uff0c\u6587\u4ef6\u5927\u5c0f\u4e0d\u53d8\u3002<\/p>\n\n\n\n
 case VSYNC_CFR:\n            \/\/ FIXME set to 0.5 after we fix some dts\/pts bugs like in avidec.c\n            if (frame_drop_threshold && delta < frame_drop_threshold && ost->frame_number) {\n                nb_frames = 0;\n            } else if (delta < -1.1)\n                nb_frames = 0;\n            else if (delta > 1.1) {\n                nb_frames = lrintf(delta);\n                if (delta0 > 1.1)\n                    nb0_frames = lrintf(delta0 - 0.6);\n            }\n            break;\ncase VSYNC_VFR:\n            if (delta <= -0.6){\n                \/\/\u4e22\u5f03 frame\n                nb_frames = 0;\n            }\n            else if (delta > 0.6)\n                ost->sync_opts = lrint(sync_ipts);\n            break;<\/code><\/pre>\n\n\n\n
\n\n\n\n
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\u6240\u4ee5\uff0c\u8c03 API \u51fd\u6570\u5b9e\u73b0\u5e27\u7387\u8f6c\u6362\uff0c\u63a8\u8350\u4f7f\u7528 fps<\/code>\uff0cframerate<\/code> \u6ee4\u955c\uff0c\u5c31\u6ca1\u6709\u8fd9\u4e48\u591a delta \u53d8\u91cf\u4e4b\u7c7b\u7684\u3002<\/p>\n\n\n\n
\n\n\n\n
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