If the sound quality is the most important for you, FLAC and ALAC are the best. These audio formats use lossless compression, so they are ideal for storing home audio collections in their original quality. The problem is that the FLAC files are about 5 times larger than MP3 or M4A files. No one I know of uses these formats in portable audio players, because it takes too much space.
Both iTunes and iPod devices support several digital audio file formats, including M4A, MP3, WAV, AIFF, and Apple Lossless, but not support FLAC. So, what the best way to transfer FLAC to iPod with high quality? You have two options: convert FLAC to M4A or to MP3. M4A is newer than MP3, provides higher quality and is intended for its replacement. With M4A you can get higher quality with a lower bitrate and file size.
Run the downloaded file audioconverter.exe to start installation, which is fast and requires no knowledge. After installation, double click on the new icon, you will see the user interface below.
Add the FLAC audio files using "Add file" or "Add folder" buttons on toolbar. If you selected option "Recurse subfolders" then you can add entire folders with FLAC files.
By default, Output Folder for audio files is a "My Music" folder. Click the "Browse" button if you need to select another folder for M4A files. If you wish to preserve original folder tree then you need to use option "Keep directory structure".
Select M4A sampling rate or keep the original sampling rate from FLAC file. Recommended bitrate for portable devices 128 kbps.
After all the settings are ready, you can start the conversion process by clicking the "Convert" button.