{"id":462,"date":"2022-01-31T18:56:38","date_gmt":"2022-01-31T10:56:38","guid":{"rendered":"http:\/\/192.168.0.122:8088\/?p=462"},"modified":"2022-06-11T03:07:57","modified_gmt":"2022-06-10T19:07:57","slug":"ffplay%e6%ba%90%e7%a0%81%e5%88%86%e6%9e%90-read_thread","status":"publish","type":"post","link":"https:\/\/www.xianwaizhiyin.net\/?p=462","title":{"rendered":"FFplay\u6e90\u7801\u5206\u6790-read_thread"},"content":{"rendered":"\n<p>\u672c\u7cfb\u5217 \u4ee5 ffmpeg4.2 \u6e90\u7801\u4e3a\u51c6\uff0c\u4e0b\u8f7d\u5730\u5740\uff1a\u94fe\u63a5\uff1a<a href=\"https:\/\/pan.baidu.com\/s\/1VpUvpLhew-nuq4Dns80mOw\">\u767e\u5ea6\u7f51\u76d8<\/a> \u63d0\u53d6\u7801\uff1ag3k8<\/p>\n\n\n\n<p>FFplay \u6e90\u7801\u5206\u6790\u7cfb\u5217\u4ee5\u4e00\u6761\u7b80\u5355\u7684\u547d\u4ee4\u5f00\u59cb\uff0c<code class=\"prettyprint\" >ffplay -i a.mp4<\/code>\u3002a.mp4\u4e0b\u8f7d\u94fe\u63a5\uff1a<a href=\"https:\/\/pan.baidu.com\/s\/1RN1xRsQDGx65MGyB_T1IzA\">\u767e\u5ea6\u7f51\u76d8<\/a>\uff0c\u63d0\u53d6\u7801\uff1anl0s \u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<p>\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u672c\u6587\u4e3b\u8981\u8bb2\u89e3 <strong>read_thread()<\/strong> \u51fd\u6570\u7684\u5185\u90e8\u903b\u8f91\u3002\u8fd9\u4e2a\u6d41\u7a0b\u56fe\u662f\u6839\u636e\u4e0a\u9762\u7684\u547d\u4ee4<code class=\"prettyprint\" >ffplay -i a.mp4<\/code> \u753b\u7684\uff0c\u6709\u4e9b\u6d41\u7a0b\u6211\u7701\u7565\u4e86\uff0c\u56e0\u4e3a\u4e0d\u4f1a\u6267\u884c\u67d0\u4e9b\u4ee3\u7801\uff0c\u6240\u4ee5\u6709\u4e9bif\u5224\u65ad\u6211\u6ca1\u753b\u51fa\u6765\uff0c\u4e3a\u4e86\u7b80\u6d01\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"757\" height=\"881\" src=\".\/wp-content\/uploads\/2022\/01\/ffplay-5-1.png\" alt=\"\" class=\"wp-image-465\"\/><\/figure>\n\n\n\n<p>\u4ece\u4e0a\u9762\u7684\u6d41\u7a0b\u56fe\u53ef\u4ee5\u770b\u51fa\uff0c <strong>read_thread()<\/strong> \u505a\u4e86\u4e00\u4e9b\u521d\u59cb\u5316\u8d4b\u503c\u5de5\u4f5c\u4e4b\u540e\uff0c\u6253\u5f00\u89c6\u9891\u6587\u4ef6\u3002\u5c31\u4f1a\u8c03 <strong>stream_component_open()<\/strong> \u5f00\u542f\u89e3\u7801\u7ebf\u7a0b\uff0c\u8fd9\u4e2a\u51fd\u6570\u7279\u522b\u91cd\u8981\uff0c\u4e0b\u9762\u4f1a\u4ed4\u7ec6\u8bb2\u89e3\u3002\u7136\u540e\u5c31\u4f1a\u8fdb\u53bb\u4e00\u4e2a for() \u6b7b\u5faa\u73af\uff0c\u4e0d\u65ad\u4ece\u6587\u4ef6\u8bfb\u53d6 <strong>AVPacket<\/strong>\uff0c\u7136\u8c03\u7528 <strong>packet_queue_put()<\/strong> \u628a AVPacket \u63d2\u8fdb\u53bb <strong>PacketQueue<\/strong> \u3002<strong>packet_queue_put()<\/strong> \u4e5f\u662f\u91cd\u70b9\u51fd\u6570\uff0c\u4f1a\u4ed4\u7ec6\u8bb2\u89e3\u3002<\/p>\n\n\n\n<p>read_thread \u7ebf\u7a0b\u505a\u7684\u5de5\u4f5c\u5176\u5b9e\u5c31\u8fd9\u4e9b\uff0c\u975e\u5e38\u5730\u7b80\u5355\u3002<\/p>\n\n\n\n<p><strong>\u91cd\u70b9\u51fd\u6570\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>stream_component_open()<\/strong> \uff0c<\/li><li><strong>packet_queue_put()<\/strong>\uff0c<\/li><\/ul>\n\n\n\n<p><strong>\u91cd\u8981\u77e5\u8bc6\u70b9\uff1a<\/strong><\/p>\n\n\n\n<p><strong>avformat_open_input()<\/strong> \u51fd\u6570\u91cc\u9762\u7684 options \u662f\u4e00\u4e2a\u4e8c\u7ea7\u6307\u9488\uff0c\u4ed6\u4f1a\u6539\u53d8\u4f60\u4f20\u8fdb\u53bboptions\uff0c\u6539\u6210\u6ca1\u7528\u5230\u7684options\u3002\u7136\u540e\u5728\u540e\u9762\u8c03\u7528 <strong>av_dict_get()<\/strong> \u5224\u65ad\u8fd4\u56de\u7684options\u662f\u4e0d\u662f\u8fd8\u6709\u503c\uff0c\u5982\u679c\u6709\u5c31\u62a5\u9519\u7ed9\u51fa\u63d0\u793a\u3002<\/p>\n\n\n\n<p>ffmpeg \u5f88\u591a\u51fd\u6570\u90fd\u662f\u5982\u6b64\u8bbe\u8ba1\uff0c\u4f8b\u5982 <strong>avcodec_open2()<\/strong>\uff0c\u4e5f\u662f\u4f20\u9012\u4e00\u4e2a \u4e8c\u7ea7\u6307\u9488\u7684 options\uff0c\u8fd4\u56de\u503c\u4e5f\u4f1a\u6539\u6210\u6ca1\u7528\u5230\u7684options\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"637\" height=\"307\" src=\".\/wp-content\/uploads\/2022\/01\/ffplay-5-2.png\" alt=\"\" class=\"wp-image-463\"\/><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<p>google_ads_content<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u4e0b\u9762\u5f00\u59cb\u8bb2\u89e3 <strong>stream_component_open()<\/strong> \u7684\u5185\u90e8\u903b\u8f91\uff0c\u6d41\u7a0b\u56fe\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"916\" height=\"634\" src=\".\/wp-content\/uploads\/2022\/01\/ffplay-5-3.png\" alt=\"\" class=\"wp-image-464\"\/><\/figure>\n\n\n\n<p>\u4ece\u6d41\u7a0b\u56fe\u53ef\u4ee5\u770b\u51fa\uff0c <strong>stream_component_open()<\/strong> \u505a\u7684\u4e8b\u60c5\u5c31\u662f\u8fd9\u6837\uff0c\u5148\u505a\u4e00\u4e9b\u89e3\u7801\u5668\u76f8\u5173\u7684\u53c2\u6570\u8d4b\u503c\uff0c\u7136\u540e\u8c03 avcodec_open2() \u6253\u5f00\u89e3\u7801\u5668\u3002\u7136\u540e\u6839\u636e\u97f3\u9891\u6216\u8005\u89c6\u9891\u505a\u4e0d\u540c\u5904\u7406\u3002\u89c6\u9891\u5c31\u76f4\u63a5\u5f00\u7ebf\u7a0b video_thread() \u8fdb\u884c\u540e\u7eed\u5904\u7406\u3002\u97f3\u9891\u5c31\u6bd4\u8f83\u590d\u6742\u4e00\u4e9b\uff0c\u4f1a\u521b\u5efa filter_graph\uff0c\u867d\u7136\u6211\u4eec\u7684\u547d\u4ee4\u53c2\u6570\u6ca1\u7528\u5230 filter\uff0c\u4f46ffplay\u4e3a\u4e86\u901a\u7528\uff0c\u8fd8\u662f\u4f1a\u521b\u5efa\u4e00\u4e2a\u7a7a\u7684filter graph\uff0c\u6682\u65f6\u4e0d\u4ed4\u7ec6\u8bb2\u89e3 configure_audio_filters() \u51fd\u6570\u7684\u5b9e\u73b0\uff0c\u540e\u9762\u518d\u5199\u4e00\u7bc7\u6587\u7ae0\u7ed3\u5408\u4e00\u6761\u5e26 <strong>-af<\/strong> \u53c2\u6570\u7684ffplay\u547d\u4ee4\u8fdb\u884c\u8bb2\u89e3\u3002\u73b0\u5728\u53ea\u9700\u8981\u77e5\u9053 \u89e3\u7801\u51fa\u6765\u7684 AVFrame \u4f1a\u7ecf\u8fc7 in_audio_filter \uff0c\u7136\u540e\u4ece out_audio_filter \u51fa\u6765\u5c31\u884c\uff0c\u56e0\u4e3a\u662f\u7a7a\u7684 filter_graph\uff0c\u6240\u4ee5AVFrame\u662f\u6ca1\u53d8\u5316\u7684\u3002<strong>audio_open()<\/strong> \u51fd\u6570\u7528\u6765\u6253\u5f00\u97f3\u9891\u8bbe\u5907\uff0c\u5176\u5185\u90e8\u5b9e\u73b0\u6bd4\u8f83\u590d\u6742\uff0c\u4e0b\u9762\u4f1a\u4ed4\u7ec6\u8bb2\u89e3\u3002<\/p>\n\n\n\n<p><strong>\u91cd\u70b9\u51fd\u6570\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>audio_open()<\/strong><\/li><\/ul>\n\n\n\n<p>audio_open() \u7684\u4ee3\u7801\u6bd4\u8f83\u5c11\uff0c\u6240\u4ee5\u4e0d\u753b\u6d41\u7a0b\u56fe\uff0c\u76f4\u63a5\u8d34\u4ee3\u7801\u8bb2\u89e3\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" >if (!wanted_channel_layout || wanted_nb_channels != av_get_channel_layout_nb_channels(wanted_channel_layout)) {\n        wanted_channel_layout = av_get_default_channel_layout(wanted_nb_channels);\n        wanted_channel_layout &amp;= ~AV_CH_LAYOUT_STEREO_DOWNMIX;\n}<\/code><\/pre>\n\n\n\n<p>\u4e0a\u9762\u8fd9\u6bb5\u4ee3\u7801\u7279\u522b\u6709\u610f\u601d\uff0c\u5728 ffplay.c \u91cc\u9762\u7ecf\u5e38\u770b\u5230\u8fd9\u6837\u7684\u5224\u65ad\uff0c\u5224\u65ad channel_layout \u8ddf channels \u662f\u5426\u5339\u914d\u3002\u5e94\u8be5\u662f\u4e00\u4e9b\u517c\u5bb9\u5904\u7406\uff0c\u5386\u53f2\u9057\u7559\u95ee\u9898\u3002\u5176\u5b9e\u6211\u4e5f\u5f88\u7591\u60d1\uff0c\u5199\u5165mp4 \u6216 flv \u6587\u4ef6\u7684\u65f6\u5019\uff0cchannel_layout \u8ddf channels\u5b57\u6bb5 \u96be\u9053\u8fd8\u4f1a\u5199\u9519\uff0c\u6240\u4ee5\u9700\u8981\u64ad\u653e\u7684\u65f6\u5019\u9700\u8981\u7ea0\u6b63\u4e00\u4e0b\uff1f\u6211\u73b0\u5728\u5199\u9879\u76ee\uff0c\u90fd\u662f\u7167\u6284\u8fd9\u79cd\u4ee3\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" >wanted_spec.format = AUDIO_S16SYS;<\/code><\/pre>\n\n\n\n<p>ffplay \u53ea\u652f\u6301 AUDIO_S16SYS \u64ad\u653e\u683c\u5f0f\uff0c\u539f\u6587\u4ef6\u5982\u679c\u4e0d\u662f\u8fd9\u79cd\u683c\u5f0f\uff0c\u540e\u9762\u90fd\u4f1a\u7528\u91cd\u91c7\u6837\u8fdb\u884c\u8f6c\u6362\u683c\u5f0f\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" >wanted_spec.samples = FFMAX(SDL_AUDIO_MIN_BUFFER_SIZE, 2 &lt;&lt; av_log2(wanted_spec.freq \/ SDL_AUDIO_MAX_CALLBACKS_PER_SEC));<\/code><\/pre>\n\n\n\n<p>\u4e0a\u9762\u7684 wanted_spec.samples \u662f\u8bbe\u7f6e SDL \u97f3\u9891 call_back\u51fd\u6570\u6bcf\u6b21\u56de\u8c03\u9700\u8981\u4f20\u9012\u591a\u5c11\u4e2a samples \u7ed9SDL\u3002\u8fd9\u4e2a\u8ba1\u7b97\u65b9\u5f0f\u6bd4\u8f83\u96be\u61c2\uff0c\u6211\u4ed4\u7ec6\u8bb2\u4e00\u4e0b\u3002wanted_spec.freq \u662f\u91c7\u7528\u7387\uff0c\u5982\u679c freq \u7b49\u4e8e48000\uff0c\u5c31\u662f\u8bf4SDL \u6bcf\u79d2\u64ad\u653e 48000\u4e2asample\u3002SDL_AUDIO_MAX_CALLBACKS_PER_SEC \u4ee3\u8868SDL\u6bcf\u79d2\u56de\u8c03\u591a\u5c11callback\uff0cSDL_AUDIO_MAX_CALLBACKS_PER_SEC \u5728\u4ee3\u7801\u91cc\u8bbe\u7f6e\u4e3a 30\uff0c\u6bcf\u79d2\u56de\u8c0330\u6b21\u3002\u90a3 (wanted_spec.freq \/ SDL_AUDIO_MAX_CALLBACKS_PER_SEC) \u81ea\u7136\u5c31\u7b49\u4e8e\u6bcf\u6b21\u56de\u8c03\u9700\u8981\u4f20\u9012\u7684sample\u6570\u91cf\u3002\u90a3\u4e3a\u4ec0\u4e48\u8fd8\u8981\u7528 av_log2() \u53d6\u6307\u6570\uff0c\u7136\u540e\u53c8\u7528 &lt;&lt; \u5de6\u4f4d\u79fb\u53d6\u5e42\u5462\uff1f\u662f\u56e0\u4e3a\u8fd9\u6837\u505a\u53ef\u4ee5\u628a samples \u8f6c\u6362\u6210 2\u7684\u500d\u6570\u3002\u4f8b\u5982 48000 \/ 30 = 1600\uff0c1600 \u5e76\u4e0d\u662f 2\u7684\u500d\u6570\uff0cav_log2(1600) \u7b49\u4e8e 10\uff0c\u7136\u540e 2 &lt;&lt; 10 \u7b49\u4e8e 2048\uff0c\u6700\u540e wanted_spec.samples \u7b49 2048 \uff0c\u662f2\u7684\u500d\u6570\u3002\u4e3a\u4ec0\u4e48\u8981\u8bbe\u7f6e\u6210 2\u7684\u500d\u6570\uff0c\u4f30\u8ba1\u662f\u4e3a\u4e86\u5bf9\u9f50\u5185\u5b58\uff0c\u8bf7\u770bSDL \u7684\u6587\u6863 <a href=\"https:\/\/wiki.libsdl.org\/SDL_OpenAudioDevice\">https:\/\/wiki.libsdl.org\/SDL_OpenAudioDevice<\/a>\uff0c\u6587\u6863\u5efa\u8bae\u8bbe\u7f6e\u62102\u7684\u500d\u6570\u3002<\/p>\n\n\n\n<p>\u63a5\u4e0b\u6765\u662f audio_open() \u91cc\u9762\u6700\u96be\u61c2\u7684\u903b\u8f91\uff0c\u8bf7\u770b\u4ee3\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" >static const int next_nb_channels&#091;] = {0, 0, 1, 6, 2, 6, 4, 6};\nstatic const int next_sample_rates&#091;] = {0, 44100, 48000, 96000, 192000};\n.....\u7701\u7565\u4ee3\u7801..\nwhile (!(audio_dev = SDL_OpenAudioDevice(NULL, 0, &amp;wanted_spec, &amp;spec, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE | SDL_AUDIO_ALLOW_CHANNELS_CHANGE))) {\n        av_log(NULL, AV_LOG_WARNING, &quot;SDL_OpenAudio (%d channels, %d Hz): %s\\n&quot;,\n               wanted_spec.channels, wanted_spec.freq, SDL_GetError());\n        wanted_spec.channels = next_nb_channels&#091;FFMIN(7, wanted_spec.channels)];\n        if (!wanted_spec.channels) {\/\/\u6ce8\u610f\u8fd9\u53e5\u4ee3\u7801\u3002\n            wanted_spec.freq = next_sample_rates&#091;next_sample_rate_idx--]; \/\/\u6ce8\u610f\u8fd9\u53e5\u4ee3\u7801\u3002\n            wanted_spec.channels = wanted_nb_channels;\n            if (!wanted_spec.freq) {\n                av_log(NULL, AV_LOG_ERROR,\n                       &quot;No more combinations to try, audio open failed\\n&quot;);\n                return -1;\n            }\n        }\n        wanted_channel_layout = av_get_default_channel_layout(wanted_spec.channels);\n}<\/code><\/pre>\n\n\n\n<p>audio_open() \u5728\u5165\u53e3\u5c31\u5b9a\u4e49\u4e86\u8fd9\u4e48\u4e00\u4e2a\u6570\u7ec4 next_nb_channels[]\uff0c0,0,1,6,2,6,4,6\u3002\u548b\u4e00\u770b\uff0c\u4e0d\u592a\u5bb9\u6613\u770b\u51fa\u6765\u662f\u5e72\u5565\u7684\u3002\u5176\u5b9e\u5c31\u50cf\u4ed6\u90a3\u53e5\u62a5\u9519\u63d0\u793a\u8bf4\u7684\u3002<\/p>\n\n\n\n<p>\"No more combinations to try, audio open failed\"<\/p>\n\n\n\n<p><strong>next_nb_channels<\/strong> \u8ddf <strong>next_sample_rates<\/strong> \u662f\u4e00\u4e2a <strong>combination<\/strong>\uff0c\u7ec4\u5408\u5c1d\u8bd5\u3002\u4e0d\u65ad\u7528 \u4e0d\u540c\u7684\u91c7\u6837\u7387\uff0c\u4e0d\u540c\u7684\u58f0\u9053\u6765\u6253\u5f00\u97f3\u9891\u8bbe\u5907\u3002\u4e3a\u4ec0\u4e48\u8fd9\u6837\u505a\uff1f<\/p>\n\n\n\n<p>\u56e0\u4e3a\u6709\u4e9b\u8bbe\u5907\uff0c\u4e0d\u652f\u6301\u64ad\u653e\u53cc\u58f0\u9053\uff0c\u53ea\u652f\u6301\u5355\u58f0\u9053\u3002\u4f46\u662f\u539f\u6587\u4ef6\u7684\u97f3\u9891\u662f\u53cc\u58f0\u9053\u7684\u3002\u8fd9\u79cd\u60c5\u51b5\u4e0b audio_open() \u662f\u5982\u4f55\u5904\u7406\u7684\u5462\uff1f\u8fd9\u65f6\u5019\uff0c<strong>next_nb_channels<\/strong> \u8ddf <strong>next_sample_rates<\/strong> \u5c31\u6392\u4e0a\u7528\u573a\u4e86\u3002<\/p>\n\n\n\n<p>\u5728 audio_open() \u7684\u903b\u8f91\u91cc\uff0c\u4f1a\u5148\u5c1d\u8bd5\u7528\u53cc\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907\uff0c\u4f46\u662f\u97f3\u9891\u8bbe\u5907\u4e0d\u652f\u6301\u53cc\u58f0\u9053\uff0cwhile \u90a3\u91cc\u5c31\u4f1a\u5931\u8d25\u3002\u7136\u540e\u8bf7\u6ce8\u610f\u8fd9\u53e5\u4ee3\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" >wanted_spec.channels = next_nb_channels&#091;FFMIN(7, wanted_spec.channels)];<\/code><\/pre>\n\n\n\n<p>\u56e0\u4e3a wanted_spec.channels \u7b49\u4e8e2\uff0c\u6240\u4ee5 next_nb_channels[FFMIN(7, wanted_spec.channels)] \u8ba1\u7b97\u51fa\u6765\u7684\u7ed3\u679c\u662f 1\uff0c\u6240\u4ee5\u4ece\u903b\u8f91\u4e0a\uff0c\u5c31\u4f1a\u4ece\u53cc\u58f0\u9053\u53d8\u6210\u5355\u58f0\u9053\uff0c\u91cd\u65b0\u8c03 SDL_OpenAudioDevice() \u51fd\u6570\u5c1d\u8bd5\u6253\u5f00\u97f3\u9891\u8bbe\u5907\u3002<\/p>\n\n\n\n<p>\u89e3\u6790\u5230\u8fd9\u91cc\uff0c\u5e94\u8be5\u6bd4\u8f83\u6e05\u695a next_nb_channels[] \u8fd9\u4e2a\u6570\u7ec4\u90a3\u58060,0,1,6,2,6,4,6 \u662f\u5e72\u4ec0\u4e48\u4e86\uff0c\u6ca1\u9519\uff0cnext_nb_channels \u5176\u5b9e\u662f\u4e00\u4e2amap\u8868\uff0c\u58f0\u9053\u5207\u6362\u6620\u5c04\u8868\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>next_nb_channels[7] = 6\uff0c\u4ece7\u58f0\u9053\u5207\u6362\u52306\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[6] = 4\uff0c\u4ece6\u58f0\u9053\u5207\u6362\u52304\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[5] = 6\uff0c\u4ece5\u58f0\u9053\u5207\u6362\u52306\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[4] = 2\uff0c\u4ece4\u58f0\u9053\u5207\u6362\u52302\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[3] = 6\uff0c\u4ece3\u58f0\u9053\u5207\u6362\u52306\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[2] = 1\uff0c\u4ece\u53cc\u58f0\u9053\u5207\u6362\u5230\u5355\u58f0\u9053\u6253\u5f00\u97f3\u9891\u8bbe\u5907<\/li><li>next_nb_channels[1] = 0\uff0c\u5355\u58f0\u9053\u90fd\u6253\u4e0d\u5f00\u97f3\u9891\u8bbe\u5907\uff0c\u65e0\u6cd5\u518d\u5207\u6362\uff0c\u9700\u8981\u964d\u4f4e\u91c7\u6837\u7387\u64ad\u653e\u3002<\/li><li>next_nb_channels[0] = 0\uff0c0\u58f0\u9053\u90fd\u6253\u4e0d\u5f00\u97f3\u9891\u8bbe\u5907\uff0c\u65e0\u6cd5\u518d\u5207\u6362\uff0c\u9700\u8981\u964d\u4f4e\u91c7\u6837\u7387\u64ad\u653e\u3002<\/li><\/ul>\n\n\n\n<p>\u4e3a\u4ec0\u4e48\u540e\u9762\u4e24\u4e2a \u662f 0\uff0c\u662f\u56e0\u4e3a\u5207\u6362\u5230\u540e\u9762\u7684\u65f6\u5019\uff0c\u5df2\u7ecf\u6ca1\u6cd5\u518d\u5207\u6362\u4e86\uff0c\u5c31\u4f1a\u5c1d\u8bd5\u964d\u4f4e\u91c7\u6837\u7387\u3002\u8bf7\u770b\u4ee3\u7801<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"prettyprint\" > if (!wanted_spec.channels) {\/\/\u6ce8\u610f\u8fd9\u53e5\u4ee3\u7801\u3002\n     wanted_spec.freq = next_sample_rates&#091;next_sample_rate_idx--]; \/\/\u6ce8\u610f\u8fd9\u53e5\u4ee3\u7801\u3002\n     wanted_spec.channels = wanted_nb_channels;\n    if (!wanted_spec.freq) {\n      av_log(NULL, AV_LOG_ERROR,&quot;No more combinations to try, audio open failed\\n&quot;);\n      return -1;\n    }\n}<\/code><\/pre>\n\n\n\n<p>next_sample_rate_idx \u5728\u5f00\u5934\u5c31\u8d4b\u503c\u4e3a \u6bd4 want \u91c7\u6837\u7387\u5c0f\u7684 index\u3002\u7136\u540e\u58f0\u9053\u90fd\u5c1d\u8bd5\u5b8c\u4e86\uff0c\u8fd8\u6253\u4e0d\u5f00\u97f3\u9891\u8bbe\u5907\uff0c\u5c31\u4f1a\u5c1d\u8bd5\u66f4\u5c0f\u7684\u91c7\u6837\u7387\uff0c\u518d\u7528\u65b0\u7684\u91c7\u6837\u7387\u7ed3\u5408\u4e4b\u524d\u7684\u58f0\u9053\u90fd\u5c1d\u8bd5\u4e00\u4e0b\u6253\u5f00\u97f3\u9891\u8bbe\u5907\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u8bf4 <strong>next_nb_channels<\/strong> \u8ddf <strong>next_sample_rates<\/strong> \u662f\u4e00\u4e2a <strong>combination<\/strong>\uff0c\u7ec4\u5408\u5c1d\u8bd5\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-css-opacity\"\/>\n\n\n\n<p>ffplay \u6e90\u7801\u5206\u6790\uff0c<strong>stream_component_open(<\/strong>) \u5206\u6790\u5b8c\u6bd5\u3002<\/p>\n\n\n\n<p>\u00a9\u7248\u6743\u6240\u5c5e\uff1a\u77e5\u8bc6\u661f\u7403\uff1a\u5f26\u5916\u4e4b\u97f3\uff0cQQ\uff1a2338195090\u3002<\/p>\n\n\n\n<p>\u7531\u4e8e\u7b14\u8005\u7684\u6c34\u5e73\u6709\u9650\uff0c 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