anybody knows if the sound quality on n810 is good or not, what about compare with normal mp3 players

No, no one knows; there's a lot of people who think they do, though, and they discussed it at great length until the thread drifted off to discuss trying to get amplifiers (USB, analog, and for all I know gamma-ray coupled) working. Search for n810 sound quality, it's the thread with audiophile in the title...

depends what you are using to listen to it. You need something with isolation, the lower the ohms, the better to get volume out of the nokia. I'm using a pair of ultimate ears superfi 5 pro's. 21 ohms, good isolation and good bass.
an excellent candidate for the N810 to turn it into a pretty good Mp3 player and movie watcher.

I have a 4th Gen iPod and the N810. Put the same set of MP3 files on both, we are talking about 128kbps up to 320kbps constant bit rate, and a couple of VBR ones for good measure.

Tested using various headphones, but the ones which really show up the difference are my Sennheiser HD280 Pros. They are 64ohms, so slightly harder to drive, but the audio quality is absolutely stunning from the N810. The iPod sounds very bland side-by-side, and turning on the equaliser on the iPod only makes it worse.

I listen to a massive variety of music, from Pendulum, Way Out West, trance and DnB through to classical and spanish guitar music, so far, I haven't found a single track which sounds better on the iPod than the Nokia, this did surprise me (pleasantly)!!

Best video performance I've found (posted in several other threads) is using DivX with 128kbps MP3 audio, so no quality issues there either. I've been told the N810 has hardware decoders for DivX/MPEG4 and MP3 audio, with the graphics chip doubling-up the pixels from 400x240 to 800x480, hence the capability to run mp3 audio decoding and full-frame video seamlessly.

Hope this helps...

Mark

sure helped me...thanks

A few points regarding the acceleration:
It's not precisely hardware, and AFAIK there's nothing to help with DivX/MPEG4 (someone correct me if I'm wrong!), but it can offload the MP3 decoding onto the DSP, which gets loaded with its own tasks. This can also be done for Vorbis and FLAC, at least, and conceivably others.

One interaction to note, though; when the DSP is doing anything, the CPU drops to 333 MHz; this is because the DSP runs slower at max CPU frequency (266 MHz is out of DSP spec):
So when dealing with heavy video, better performance is possible by dropping the DSP back to 133 (still enough to decode mp3 realtime), and boosting the CPU to 400. Unfortunately, this cannot be done automatically, at present, and isn't horribly easy by hand.