I'm on MacOSX Lion and would like a method for converting webm to mp4 (or another iTunes compatible format).
ffmpeg seems like a possibility but the documentation is a bit obtuse for me; step-by-step directions would be appreciated.
If you want to use
ffmpeg, go and either
If you downloaded it manually (not with Homebrew), I would suggest copying the
ffmpeg executable file to your PATH, so that you can use it from the Terminal. Let's say you downloaded it to
~/Downloads/ffmpeg/ffmpeg, then do:
sudo mkdir -p /usr/local/bin sudo cp ~/Downloads/ffmpeg/ffmpeg /usr/local/bin/ sudo chmod +x !$ /usr/local/bin/ffmpeg
Convert to MP4
Now, by "to MP4", I assume you mean to use H.264 and AAC as video and audio codecs, respectively. For that, the basic command would be:
ffmpeg -i input.webm -c:v libx264 -c:a aac -strict experimental -b:a 192k output.mp4
If you want to control the quality, have a look at the x264 encoding guide. It is set with the
-crf option, where the default is 23, and lower means better quality (typical values are from 18 to 28). In the above example it uses the default quality of 23 for video, and 192 kBit/s constant bitrate for audio.
As for audio, the static builds do not support
libfdk-aac, but if you have support for it, you should use that instead:
ffmpeg -i input.webm -c:v libx264 -c:a libfdk_aac output.mp4
FDK-AAC gives you better quality than the internal AAC encoder. For controlling audio quality, see the AAC encoding guide.
This is, what I just used successfully on FreeBSD to create MP4-files, that MacOS would recognize as such:
ffmpeg -i input_filename -acodec aac -b:a 128k -vcodec mpeg4 -b:v 1200k -flags +aic+mv4 output_filename.mp4
I started with the command-line using this tutorial, but had change
aac because the latter was not found...
There must be some special kind of madness affecting programmers in the domain of multimedia codecs, that causes them to subtly change the command-line options from one release to another.