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Topic: Comparing MPC and OGG at same bitrate (Read 8222 times) previous topic - next topic
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Comparing MPC and OGG at same bitrate

Reply #25
tw101,

I think you're right, in a way.

The cheap plastic boxes that come with PCs (and are laughing called speakers) won't let you hear any real trebble or bass. Hence, any problems in these frequency ranges are inaudible to you.


But there are issues far beyond that. A typical $500 system sounds quite rough compared to a real hi-fi. Now, if the main problem with an encoder is that it makes the audio sound quite "rough", then you're not going to notice this on the rough sounding stereo. Whereas it will be obvious over a better system.

Before you all jump in and say "what kind of artefact is ROUGH?" I'll tell you. Listen to Lame GSYCHO encoding youcantdothat.wav at 128kbps. In the background, there's loads of encoding noise. It's obvious as noise (to me). But if you reduce the noise level, it sounds less and less like there's distinct "added noise", and more like the signal is simply "rough". There's a point where it isn't noticeable anymore. I suggest that this roughness is added by cheap stereo equipment too - poor tansducers (and let's be honest here - ALL transducers are poor compared to the rest of the signal chain) often add such distortion.

So it's quite conceivable that, at the point where this noise/distortion/roughness just becomes inaudible on your equipment (because your equipment's own distortion is hiding the codec's distortion), you may still be able to hear the codec distortion on a higher quality system.


And there's another interesting idea: All psychoacoustic data has to be measured using real world equipment. Lame is tuned by people listening to music via their hifi; psychoacoustic data (e.g. noise masking tone and tone masking noise threasholds) are measured by people listening to test signals via a rather intriguing choice of equipment (crap would sometimes be one word for it). In both these cases, the ears of the listener may be the limiting factor, but maybe the limit is imposed by the test equipment. Maybe all this psychoacoustic data measures not only human performance limits, but also the limits of the equipment.

And when you or I listen to stuff through a "normal" stereo, it's OK. But when someone refines a speaker so that the distortion is one or two orders of magnitude lower than what's commonly in use, then all the junk that was hidden by the distortion of normal speakers is now revealed. And all the measurements carried out with "normal" speakers are simply wrong - they suggest that humans can't hear such a distortion, when in fact they can.


That said, I can detect most artefacts (not ringing - it's above my hearing range, and not subtle noise pumping) via $15 Sony ear buds connected to an onboard sound card. Hearing artefacts is probably half training, half hearing ability (but not in the conventional sense). Hearing things that are so subtle that you can't really call them "artefacts" may be down to equipment. But having advanced that argument, it's still amazing what I can hear over those sony ear buds! I'd suggest that most artefacts are much more obvious over headphones than speakers.


To your friends (they're not audiophiles - audiophiles won't use a PC as a sound source, never mind using mp3!!!) suggest alt preset insane. It's better than just -b 320.

Final thought: when it comes to sound stage and resolution, the best recordings, encoded at 128kbps into mp3, will still sound better than average recordings played straight off the CD!


Cheers,
David.
P.S. nothing I'd said is to be taken as indisputable fact. ;-)
P.P.S. but I have experienced what I've described here - it's usually half decent mp3s, which sound OK on modest equipment, though you could spot artefacts with careful listening and ABX. Played over really good equipment, they just sound terrible! However, sometimes you can find the opposite - the good equipment brings out the music, but the poor equipment lays the artefacts bare. It just depends on the music and the codec.