Ubuntu – Converting FLAC to ALAC, preserving tags – in a script

In Ubuntu, you can open a terminal, navigate to the directory in question, and do the following command loop:

for f in *.flac; do ffmpeg -i "$f" -acodec alac "${f%.flac}.m4a"; done

• Will convert all .flac files in the directory to .alac files, doing so in a bit-perfect way.
• ffmpeg doesn't come packaged with Ubuntu, so you'd need to install that from repos; however, I can't say for sure that this will keep your BPM tag info.

Also, it would seem that getting iTunes to play FLAC files (and properly downconvert them to use space efficiently on my iPod) is pretty much impossible.

There's a program called flukeformac that may allow you to play .flac files in iTunes.
As to conversion for efficient iPod use, the following command loop will do the trick:

for file in *.flac; do $(flac -cd "$file" | lame --preset fast extreme - "${file%.flac}.mp3"); done`

• You may want to replace --preset fast extreme with a lower bitrate option
  (more on lame presets)

You say you are using Windows command shell, but the first command line you showed (the one that starts "for file in") doesn't look like Windows, more like some kind of Linux shell command. The second one won't work because ffmpeg won't accept a wildcard as an input file spec.

This one line Windows command does what you seem to want, to make ffmpeg (using your options above) take as its input, in turn, each flac file in the current folder and output, in the same folder, an mp3 file with the same name before the extension:

At prompt:

for %A in (*.flac) do ffmpeg  -i "%~nA.flac"  -c:v copy  -b:a 320k  "%~nA.mp3"

If the mp3 file already exists, ffmpeg will ask if you want to overwrite it.

Note: the above command is crafted for the command prompt. It won't work in a batch script. For that, you need to double all the percent signs (%) like this

In batch (cmd) script:

for %%A in (*.flac) do ffmpeg  -i "%%~nA.flac"  -c:v copy  -b:a 320k  "%%~nA.mp3"