I run an internet radio station. We encode our audio into MP3 at 128kbit, joint-stereo 44.1kHz, with LAME. Obviously there are limits to the quality that can be achieved with this bandwidth... that's not my question.
I would like to know if there is any sort of pre-processing we can do with the audio to improve the sound of the resulting compressed audio, reducing the compression artifacts a bit. I've noticed that some internet radio stations sound better than most. Hot 108 Jams comes to mind. I don't know if they're doing anything special, but my ear tells me it is better than many other stations.
Some thoughts I've had:
- Low-pass filter around 17kHz or 18kHz
- Using a compressor and/or expander to reduce the dynamic contrast
I plan to start experimenting soon. Are there any suggestions you have for things to try?
Again, my goal is to build a signal chain in such a way to reduce the artifacts introduced during the MP3 encoding process. I am hoping to create a source signal that lends itself to being encoded into MP3,while sticking to the original signal as close as possible.
Our source material is varied. We play a wide variety of genres, from a wide variety of media. Mostly everything is digital. Much of our material is in MP3 format already. (Sadly, the smaller labels find this to be an appropriate form of digital distribution.) So, many cases we are re-compressing already MP3 compressed audio.
I hope to find a balance between tweaking the signal and leaving it alone, where the resulting 128kbit MP3 stream sounds best, and closest to the source material.