<d.w.o> codecs: Music Tests

Here is the clincher. The fact of the matter is, most people don't encode sine waves or DTMF tones, and most of the popular content out there isn't speech, either. It's music. So I picked a nice 36-second sample of Brazilian music, Bermimbau's "Mandrake Som" from Blue Brazil.

funky music sample (6.3 MB)

Microsoft Audio v4.0

At 20kbps, MSA4 is definitely carrying the upper frequencies, but they are "drowning." Listen carefully to how short and crisp the syncopated hihat sounds in the WAV file and then how long and watered down it sounds in the 20kbps version. I think what is so immediately surprising about MSA4 is that it bothers to try and encode the higher frequencies at all: we're not used to hearing that from a modem-rate codec. But now we see why, perhaps, other codecs steered clear of that area -- high-frequency anomalies can be quite annoying. Even at 44kbps, the higher frequencies are still being swished around. RealPlayer, to counter, just hacks the signal down to a frequency range that it's comfortable with. As a result, the files are soft and easy to listen to, even if lacking crispness. To the credit of MSA4, the overall quality is much higher than the other codecs and the dynamic range is excellent.

RealAudio

20 kbps (95 KB)
32 kbps (154 KB)
44 kbps (209 KB)
64 kbps (303 KB)
97 kbps (457 KB)

The 20kbps is not very nice to listen to; it feels kind of like sitting in a middle seat in coach class on a 12-hour flight: all of the sound is packed in to too low a frequency range. The 32kbps version is listenable, but not quite yet pleasant. At 44kbps the music, to me, breaks some gray border between "listenable" and "funky" - the music is now genuinely enjoyable, with the hihats and percussion properly accounted for. The 64kbps version fills out the sound a bit more, but the 97kbps version seems to have little further to add.

MP3

Note that the RealPlayer G2 will choke on the VBR files, inserting large quantities of silence. Their VBR support is obviously not quite polished. We see here once more the classic playoffs of sampling frequency and stereo vs. mono. The music becomes listenable at 64kbps. While not encoded above (gosh, I'm getting tired!) the 128kbps version adds a small amount of clarity and crispness to the sounds. Notably, the VBR (highest) encoding is effectively transparent. I haven't been able to find a file that encoded poorly with VBR on its highest setting: it will just suck up more bits. This is ideal for archiving music, as it doesn't sound lossy at all, even for very high-fidelity clips (I have an excellent hirate VBR clip of Sting's "Hounds of Winter" that just blew me away - I may put up part of it at some point).

Recommendations

While I have yet to put up more music here, I would say that in general MSA4 encodes low/mid frequency music excellently and that you should run to encode most of your techno / drum&bass / house music right away with it. For those of you that love folk, classical, or hifi audio, I'd either use MSA4 with a very high bitrate or MP3 VBR at the highest setting. Given that it's free to stream MP3s and that you can make and listen to them on a diverse array of platforms (versus just MS's), and given the relatively lossless character of VBR (highest), I'd vote for that right now. If you're already with a RealAudio framework, try to provide a 44kbps stream for those of us at universities and at work who have fast enough connections: the music is an entirely different (better!) experience when it is clean! Most people have G2 at this point, or are willing to get it, so I would opt to use it. Although not covered here, the G2 codec is significantly cleaner & nicer than the RA5 & RA3 Dolbynet-based codecs. It's worth the move up.

Shame on RealNetworks for making all of their free tools difficult and hard to access. RN cannot continue trying to pimp their customers, or people will move to more pleasant and more powerful frameworks, like MS Audio and/or MP3.

One last thing: I came into this report wanting to dislike MS Audio v4.0. But it has shown itself admirably, and seems to be based entirely on in-house, proprietary work. While I loathe closed standards and the way they've tied the codec to their own expensive products, the codec is of extremely high quality, possibly better than AAC (although I need some listening tests for that!). Kudos to the quiet brains that made it.

I'll be making additions and modifications to this document as they come in. Please feel free to tell me what you thought of the report, what's wrong with it, where you have something to add, or where you'd like me to put a sample of yours.

UPDATE: Microsoft did send me an email. In fact, I got an email from Microsoft's Codec Group Manager, Amir. Here's what he said. It's worth a read as he pointed out some important technical flaws in the resampler bundled with MS Audio 4.0 that may have caused the high-frequency errors. They are working on improving their resampler but suggest in the meantime that anyone using MS Audio should downsample on their own before encoding. I will downsample before encoding my next round of tests.

<david.weekly.org>		July 25	2008