m4a も作れます。
ffmpeg -i input.wav -c:a libfdk_aac -b:a 128k output.m4a
ビットレート指定が必須です。
ffmpeg は libfaac
libfaac が入れられていることが重要
takuya@air:~/Desktop$ brew info ffmpeg ffmpeg: stable 1.2.4, devel 2.1, HEAD http://ffmpeg.org/ /usr/local/Cellar/ffmpeg/1.2.4 (168 files, 28M) * Built from source with: --with-libvorbis, --with-freetype, --with-openjpeg, --with-tools, --with-ffplay, --with-rtmpdump, --with-libass, --with-openssl, --with-fdk-aac, --with-libvpx From: https://github.com/mxcl/homebrew/commits/master/Library/Formula/ffmpeg.rb ==> Dependencies Build: pkg-config ✔, texi2html ✔, yasm ✔ Recommended: x264 ✔, faac ✔, lame ✔, xvid ✔ Optional: freetype ✔, theora ✔, libvorbis ✔, libvpx ✔, rtmpdump ✔, opencore-amr ✔, libvo-aacenc ✔, libass ✔, openjpeg ✔, speex ✘, schroedinger ✔, fdk-aac ✔, opus ✘, frei0r ✘, libcaca ✘ ==> Options --with-fdk-aac Enable the Fraunhofer FDK AAC library --with-ffplay Enable FFplay media player --with-freetype Build with freetype support --with-frei0r Build with frei0r support --with-libass Enable ASS/SSA subtitle format --with-libcaca Build with libcaca support --with-libvo-aacenc Enable VisualOn AAC encoder --with-libvorbis Build with libvorbis support --with-libvpx Build with libvpx support --with-opencore-amr Build with opencore-amr support --with-openjpeg Enable JPEG 2000 image format --with-openssl Enable SSL support --with-opus Build with opus support --with-rtmpdump Enable RTMP protocol --with-schroedinger Enable Dirac video format --with-speex Build with speex support --with-theora Build with theora support --with-tools Enable additional FFmpeg tools --without-faac Build without faac support --without-lame Disable MP3 encoder --without-x264 Disable H.264 encoder --without-xvid Disable Xvid MPEG-4 video encoder
