I first noticed this some 2 years ago. I've got a HP Jornada 568 PocketPC with a 256MB CF card which i use as MP3/OGG/MPC player, i know this is hardly the best way to listen to music, but it's better to use the hardware i have than shell out for something new.

The problem is, i hear noticeable artifacts when playing OGG's with certain types of music, most notably continous low tones. A good example where this happens is the start of Radiohead - Lucky. It sounds like there is some weird higher harmonic in it, i can't really describe it, but it's very audible to me.

Mac explained to me this is what you can hear when you reduce bit depth without dithering. Since PocketPC's as far as i'm aware don't have any floating point units and therefore can't use the normal Vorbis decoder, it would appear this is a bug in Tremor. I've tried two different programs to play OGG's on the PocketPC, PocketDiVX (later renamed to PocketMVP) and BetaPlayer, it makes no difference.

Because the issue might also be something other than Tremor and i can't decode to a wav file on my PocketPC, i have no way of verifying this and putting some samples online for everone to listen to. Is there a Tremor compile for windows i can use to confirm this?

http://www.rarewares.org/files/ogg/oggdecT.zip

Thanks for the link.

Seems the issue is with the PocketPC, tremor decoded files seem to sound fine on my PC even with no dithering. Are there perhaps older versions of Tremor that behave differently?

I think I'm right in saying that there has never been a formal release of Tremor. The library code was, IIRC, intended to be little more than a 'starting point' for the creation of environment specific implementations. I seem to recall having to tweak it slightly to get it to fly in the win32 environment; an environment that is hardly its intended target!!

I believe there have been few, if any, changes to the reference libs since initial availability.

None of this really answers your questions, but sets a little background, hopefully!!

Even if it doesn't answer my question, it still makes tremor being bugged on my PocketPC entirely plausible even if it's fine on my PC i guess.

Also explains why Vorbis is relatively hard to find on hardware players, shame really as such a thing would be an important factor in ensuring your codec's success and broad acceptation...

If anything, Tremor has seen quite a lot more development than the 'standard' Vorbis decoding code, including IIRC the first implementation of a libogg2-style demuxer with zero-copy. The development, however, has mostly been tucked away on a side-branch of CVS, and, as you say, doesn't see formal releases.

As a side-point to the side-point, Tremor is actually very easy to build almost anywhere; I'm shipping win32 and Linux/x86 software using Tremor as the preferred decoder, for footprint reasons. Back on topic somewhat, Tremor in low-precision mode often demonstrates an unpleasant sort of mechanical buzzing edge to the output, but normal-precision Tremor was 'good enough' for me. I hope no-one is shipping player products using low-precision Tremor mode, but...

Low precision mode you say.. that might be it. A quick benchmark on my 206Mhz StrongARM PocketPC gives a maximum playback rate of ~450%, and this is with the actual sound playing like an overspeeding tape recorder, so it's spending some CPU cycles on resampling as well. Could these sort of speeds indicate low precision mode being used?

Edit: That's for a Q5 file encoded at 161Kbps.

Both PocketMVP and BetaPlayer uses low-precision mode Using EVC (no ARM inlines) the none low-precition mode is much slower and these two player are mainly focus on video playback so speed does make a big difference. Later I will try to use GCC for tremor compiling...

It'd be nice if it were possible to use normal precision when playing audio only even if it sacrifices some battery life. Does anyone know the developers?

EDIT: Nevermind

You missed a good player for PocketPC
It is GSPlayer. It supports mp3/ogg and plugins.
http://hp.vector.co.jp/authors/VA032810/

I was just stating which players use low-precision for sure.
Btw there is another good open-source audio player for PocketPC called MortPlayer...

Hi all,
I'm searching for a new algorithm for mdct_backward function of Tremor lowmem and I found that Johannes Sandvall, Erik Montnemery implemented it before (http://lists.xiph.org/pipermail/tremor/2003-November/000905.html).
The lowmem tremor with a new mdct backward function was available. I goto the link: http://www.sandvall.nu/patch but this link was dead .

Could someone please send me this patch?

Thanks in advance