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Spacial Audio mp3 encoder vs Oddcast (LAME) encoder

G

GeneSavage

I'm going a little crazy here and I'm hope somebody can help relieve the stress for me... this is SUPPOSED to be FUN...

I've been running, reasonably happily, with the Spacial Audio Winamp plugin, initially purchased to stream mp3PRO but later changed back to mp3, at 96KHz, for several years. We always sounded a tad dull compared to the source material, but I figured what could you expect from something crushed down into 96k?

Someone with a 'scope pointed out to me that my highs were flat-topped at 11KHz, and said I ought to be able to do at least 15KHz with the right encoder, & I ought to be able to clean up some of the high-frequency artifacts I had, as well.

He was right about those points; with the latest LAME codec (feeding through Oddcast 3.0, built in to my streaming software) I'm getting just over 15KHz and the sound in general is more solid.

MOST of the time.

After listening for not too long of a time, I became aware that on some songs, there's a... gurgle... a tremble, a flutter, a micro-stutter, that isn't high-frequency based... it's down in the mid-range! I was not aware of any such distortion using the old encoder.

Listening to it now on two songs, it seems to mainly affect the human singing voice, especially when holding notes. Another description of the sound might be little micro-jumps in the volume at a rapid pace, not massive volume swings but jUst ENoUgH ThaT It sTARtS tO souND sTrAngE. (pip, pop, pop, pip...)

now a dense, bright song with long vocal notes is playing and it's not doing it! AARUGH!!!

(This is NOT happening with my source, and it wasn't happening with the old encoder.)

Here are my questions:

Does anybody know what codec the Spacial Audio encoder is using (perhaps Fraunhofer)?
Is the codec manually upgradeable to go to 15KHz (as Spacial Audio hasn't yet responded to my e-mail)?
Is there anything I could do, either in Oddcast or with a configuration file / line command to improve the fidelity on LAME?

I realize 96kbps is never going to be confused with CD quality, but I want to get it as clean as possible... and I feel like there's just something I'm missing that could (literally) clear this up.

HALP! (thank you.)
 
First off, make sure you listen on a variety of players as I was chasing problems only to discover it was related to the version of Winamp that I was using as my reference monitor.

When I had my oldies webstream I was using Spacial's Simplecast encoder instead of the Winamp plug-in. I don't know if there's any difference between the two and it's been some time since I ran my stream, but I noticed Simplecast gave me a great sound when paired with my Optimod 6200 DAB processing.

I think there may be different codecs in the Simplecast encoder, including the "official" FHG codec. I'd be interested if anybody has done more definitive testing not only of the Winamp plug-in, but the Simplecast encoder, too.
 
I researched part of the answer with an audio spectrum analyzer recently while choosing a stand-alone Shoutcast encoder. Essentially, Oddcast beats the Shoutcast encoder for high end response at any given bitrate. You can do a solid 15kHz mp3 stereo with Oddcast at 96kHz 44.1 or 32 kHz. With Shoutcast, it's more like 12.5 kHz. At 48 kbps mono, it's 12 kHz vs 10 kHz. 40 kbps mono, 10 kHz. vs. 8 kHz. Artifacting seems consistentaly better with Oddcast, too.

Lacking a spectrum analyzer, check your audio editing program to see if it does a spectrum analysis that's detailed enough to get a good look at the high end of a 44.1 kHz. or 48 kHz. wav recording of your stream.
 
I vaguely remember seeing this issue a few years back with the Spacial encoder when I used SAM. I found the frequency response was muted in the high end and I recall a discussion that it seemed chopped at 10kHz which made sense if you were sampling at 22.050kHz but at 44.1kHz that should have passed through.

In v3.5 of SAM they changed their encoders and whilst the stereo performance was vastly improved with better frequency response (i.e. they sorted the above out), the screwed the mono settings, in that most internet radio encoders tend to peak around 0 to -1dBfs and so when the mono was summed, it crashed into the clippers and sounded distorted (my old BBC training was (A+B) - 3dB for mono. I actually had to use their Winamp plugin as a plugin to SAM to generate a clean 24kB/s mono MP3. They ignored my emails on the subject.

Now that I'm on Station Playlist with their Oddcast encoder, all is a lot cleaner.
 
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