{"id":2210,"date":"2015-01-26T10:12:47","date_gmt":"2015-01-26T06:12:47","guid":{"rendered":"https:\/\/rakhesh.com\/?p=2210"},"modified":"2015-01-26T10:12:47","modified_gmt":"2015-01-26T06:12:47","slug":"quick-ffmpeg-tricks-extract-audio-convert-audio-codec-of-a-video","status":"publish","type":"post","link":"https:\/\/rakhesh.com\/gadgets\/quick-ffmpeg-tricks-extract-audio-convert-audio-codec-of-a-video\/","title":{"rendered":"Quick ffmpeg tricks (extract audio, convert audio codec of a video)"},"content":{"rendered":"<p>I use <a href=\"http:\/\/ffmpeg.org\/\" target=\"_blank\">ffmpeg<\/a> to convert between audio and video formats. Two situations I use it for are: (1) when I have a video whose audio codec is of a format my media players can&#8217;t handle (I use <a href=\"http:\/\/www.wdc.com\/en\/products\/products.aspx?id=1270\" target=\"_blank\">WD TV Live<\/a> and it has trouble with certain formats), or (2) when I want to extract the audio only from a video.\u00a0<\/p>\n<p>For converting only the audio here&#8217;s the command I use:<\/p>\n<pre class=\"lang:batch decode:true\">c:\\&gt; ffmpeg -i \"input file.xxx\" -vcodec copy -acodec libmp3lame \"output file.xxx\"<\/pre>\n<p>The syntax is pretty obvious. The input file is taken, the video codec is copied as-is to the new file, the audio codec is re-encoded to mp3. I could have used <code>-acodec mp3<\/code> too. In the past there used to be an in-built mp3 encoder as well as the mp3 encoder provided by the LAME project (ffmpeg must be built with LAME\u00a0encoder via the <code>--enable-libmp3lame<\/code> switch for this to work) so you could choose between either via the two switches, but now there&#8217;s no in-built encoder so both <code>--acodec mp3<\/code> and <code>--acodec libmp3lame<\/code> do the same.\u00a0<\/p>\n<p>To confirm what switches ffmpeg was built with simply run the command. For example, on my machine:<\/p>\n<pre class=\"lang:batch decode:true\">c:\\&gt; ffmpeg\r\nffmpeg version N-68788-g37b35fe Copyright (c) 2000-2014 the FFmpeg developers\r\n  built on Dec 30 2014 22:02:25 with gcc 4.9.2 (GCC)\r\n  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnu\r\ntls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-\r\nlibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-l\r\nibrtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --\r\nenable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --ena\r\nble-libxvid --enable-lzma --enable-decklink --enable-zlib\r\n  libavutil      54. 15.100 \/ 54. 15.100\r\n  libavcodec     56. 19.100 \/ 56. 19.100\r\n  libavformat    56. 16.102 \/ 56. 16.102\r\n  libavdevice    56.  3.100 \/ 56.  3.100\r\n  libavfilter     5.  6.100 \/  5.  6.100\r\n  libswscale      3.  1.101 \/  3.  1.101\r\n  libswresample   1.  1.100 \/  1.  1.100\r\n  libpostproc    53.  3.100 \/ 53.  3.100\r\nHyper fast Audio and Video encoder\r\nusage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...<\/pre>\n<p>Notice it was built with <code>--enable-libmp3lame<\/code>.\u00a0<\/p>\n<p>When it comes to extracting just the audio from a video there&#8217;s two ways to do it: 1) you can simply extract the audio in the codec as it is, or 2) you can extract &amp; convert to the codec you want. The latter has the disadvantage that if the original video is in a lossy audio codec, converting will result in some degradation of quality.\u00a0<\/p>\n<p>To check what audio codec the file is in, do the following:\u00a0<\/p>\n<pre class=\"lang:batch decode:true\">c:\\&gt; ffmpeg -i \"input file.m4a\"\r\nffmpeg version N-68788-g37b35fe Copyright (c) 2000-2014 the FFmpeg developers\r\n  built on Dec 30 2014 22:02:25 with gcc 4.9.2 (GCC)\r\n  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnu\r\ntls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-\r\nlibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-l\r\nibrtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --\r\nenable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --ena\r\nble-libxvid --enable-lzma --enable-decklink --enable-zlib\r\n  libavutil      54. 15.100 \/ 54. 15.100\r\n  libavcodec     56. 19.100 \/ 56. 19.100\r\n  libavformat    56. 16.102 \/ 56. 16.102\r\n  libavdevice    56.  3.100 \/ 56.  3.100\r\n  libavfilter     5.  6.100 \/  5.  6.100\r\n  libswscale      3.  1.101 \/  3.  1.101\r\n  libswresample   1.  1.100 \/  1.  1.100\r\n  libpostproc    53.  3.100 \/ 53.  3.100\r\nInput #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input file.m4a':\r\n  Metadata:\r\n    major_brand     : dash\r\n    minor_version   : 0\r\n    compatible_brands: iso6mp41\r\n    creation_time   : 2013-06-28 19:39:02\r\n  Duration: 00:04:22.08, start: 0.000000, bitrate: 255 kb\/s\r\n    Stream #0:0(und): Audio: aac (LC) (mp4a \/ 0x6134706D), 44100 Hz, stereo, fltp, 253 kb\/s (default)\r\n    Metadata:\r\n      creation_time   : 2013-06-28 19:39:02\r\n      handler_name    : SoundHandler\r\nAt least one output file must be specified\r\n<\/pre>\n<p>Notice it identifies the audio stream as AAC in this case. If I am happy with extracting that as it is I can do the following:<\/p>\n<pre class=\"lang:batch decode:true \">c:\\&gt; ffmpeg -i \"input file.m4a\" -vn -acodec copy \"output.aac\"<\/pre>\n<p>The <code>-vn<\/code> switch tells ffmpeg to ignore the video. The <code>-acodec copy<\/code> switch tells it to copy the audio codec as it is. Since this is an AAC file, I assign an extension of <code>.aac<\/code> to the output file.\u00a0<\/p>\n<p>However, if I didn&#8217;t want the audio stream as AAC, I would have done the following:<\/p>\n<pre class=\"lang:ps decode:true\">c:\\&gt; ffmpeg -i \"input file.m4a\" -vn -ac 2 -ar 44100 -ab 320k -acodec libmp3lame \"output.mp3\"<\/pre>\n<p>Here I am converting the audio to mp3. Once again I ignore the video via <code>-vn<\/code>. I specify the audio codec via <code>-acodec libmp3lame<\/code>. The rest of the switches are as follows:<\/p>\n<ul>\n<li><code>-ac 2<\/code> =&gt; two channels (stereo) (note this is same as the input, so is an optional switch)<\/li>\n<li><code>-ar 44100<\/code> =&gt; sammple rate 44100 Hz (CD quality) (note this is same as the input, so is an optional switch)<\/li>\n<li><code>-ab 320k<\/code> =&gt; bit-rate of 320 kb\/s (if I don&#8217;t specify this the bit-rate will be 128 kb\/s for mp3)<\/li>\n<\/ul>\n<p>Essentially, instead of just copying the audio codec you convert it. Otherwise the idea is the same. Apart from <code>libmp3lame<\/code> (or <code>mp3<\/code>) I could have also used the following audio codecs: <code>vorbis<\/code> (for ogg), <code>aac<\/code>, <code>flac<\/code>, and <code>wma<\/code>.\u00a0<\/p>\n<p>Before concluding, here&#8217;s a link to <a href=\"http:\/\/www.ffmpeg.org\/ffmpeg.html\" target=\"_blank\">ffmpeg&#8217;s documentation<\/a> (for all the command-line switches etc). Also, <a href=\"http:\/\/howto-pages.org\/ffmpeg\/\" target=\"_blank\">this is a good page<\/a> on audio\/ video containers and ffmpeg. The latter is a very thorough and informative page, I am sure I&#8217;ll be referring to it in the future.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I use ffmpeg to convert between audio and video formats. Two situations I use it for are: (1) when I have a video whose audio codec is of a format my media players can&#8217;t handle (I use WD TV Live and it has trouble with certain formats), or (2) when I want to extract the &hellip; <a href=\"https:\/\/rakhesh.com\/gadgets\/quick-ffmpeg-tricks-extract-audio-convert-audio-codec-of-a-video\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Quick ffmpeg tricks (extract audio, convert audio codec of a video)<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[65,85],"tags":[455,453,452,454],"jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts\/2210"}],"collection":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/comments?post=2210"}],"version-history":[{"count":0,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts\/2210\/revisions"}],"wp:attachment":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/media?parent=2210"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/categories?post=2210"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/tags?post=2210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}