First of all, I know very little about acoustics. People in the know should feel free to point out my mistakes.
Yesterday I read that the Heroes IV Soundtrack CD is converted from MP3 files of 128 kbps - 192 kbps quality. The source cited its frequency range as proof: its frequency never goes above 16000Hz.
My current understanding is:
- High quality audio should utilize the full frequency range, often going above 20000 Hz;
- For the purpose of compression, MP3 files cap their frequency. This would be especially obvious with 128 kbps files.
The difference can be seen using the shareware Cool Edit / Adobe Audition's "spectral view" mode. High quality audio fills up the whole graph, while MP3 files (except those with the least compression) are "cut off" above a certain point. (I don't know whether the open-source software Audacity has this mode.)
So I began examining the music of the Heroes series with this knowledge.
1) CD tracks of Heroes II
Example: POL Barbarian theme, left channel
Has full frequency range.
2) Heroes III in-game MP3 (128 kbps)
Example: Necropolis theme, left channel
For the most part the frequency is generally capped at a point near 16000 Hz, only reaching above it in a few portions.
3) Heroes IV in-game MP3 (128 kbps)
Example: Credit theme, left channel
Capped at a point near 16000 Hz, with a few higher spikes, not unlike Heroes III.
4) Heroes IV OST CD
Example: Credit theme, left channel
Hey, what's this? Why does an audio CD have a narrower range than 128 kbps MP3!? The spikes are hardly visible now.
So the unfortunate news is, unless my Heroes IV OST is a bootleg, the audio quality of Heroes IV OST CD is on par with, or even lower than the MP3 files in-game.
(To be continued in the next post.)
