Цитата:
You can convert any audio format to Ogg Vorbis. However, converting from one lossy format, like MP3, to another lossy format, like Vorbis, is generally a bad idea. Both MP3 and Vorbis encoders achieve high compression ratios by throwing away parts of the audio waveform that you probably won't hear. However, the MP3 and Vorbis codecs are very different, so they each will throw away different parts of the audio, although there certainly is some overlap. Converting a MP3 to Vorbis involves decoding the MP3 file back to an uncompressed format, like WAV, and recompressing it using the Ogg Vorbis encoder. The decoded MP3 will be missing the parts of the original audio that the MP3 encoder chose to discard. The Ogg Vorbis encoder will then discard other audio components when it compresses the data
Короче так оно и есть - настоящие эстеты должны кодировать в огг с исходника :).