A year or two ago I bought a CD-MP3 player (Egoman LA310) - seemed a good buy at the time since not too many supported ID3 tags in the price range. I've not used it a lot, still less with MP3s, but recently I realised that all tracks encoded as joint stereo were playing as mono. Sometimes it seemed that the first couple of seconds were in stereo.

The short answer is obviously that I need to ditch it and get a decent one - doubtless I'll get around to it. But the short answer isn't interesting. As for the not-so-short answer...?

So what's going on here? Is it simply that it doesn't have enough processing power, or has it got to be a simple bug in the firmware? I've long suspected it's underpowered as you get dropouts if you select any of the equaliser settings. (Not that I want to use them.) Yet in tests down to 56kbps, it was still playing mono. Perhaps the nature of the fault is obvious to someone who understands how decoding works.

Is this a syndrome that's been heard of before?

And I presume there's no simple way to recode joint stereo as real stereo, short of un-encoding and re-encoding?

- Philip

If MP3 has too low a bitrate, it will go into "Intensity Stereo" mode, which basically is Mono with another parameter trying to point out where the sound is coming from, with what proportion (CMIIW)

If that is the case, the only way to recover is to re-encode from the source, and make sure that the bitrate is not too low.

I presume the files play fine on your computer, etc.? If so, I don't think what pepoluan has said will apply.

pepoluan: depends on the encoder. LAME has no intensity stereo, but FhG does. And afaik, it only kicked in at 96kbps or 112kbps and lower.

I would call this a firmware bug more than anything.

Well, OP indicated that he/she tried down to 56kbps. So I suspected such.

Of course it may also be a firmware bug.

I guess then dv1989's suggestion is good: Try the MP3's on your PC first. If they run perfectly, then the player is to blame.

Files play perfectly on a PC so it's certainly the player at fault, and can't be intensity stereo. Gotta be a firmware/design fault of some sort, but it puzzled me that first few seconds tend to come out in stereo. If not, it tends to skip the first few seconds. I definitely need a new player, but the engineer in me is intrigued by the symptoms.

In you situation the tiny engineer in me would make a few test wave files with various stereo content. Like "completely different L and R signals with an additional L+R mono signal", "partially mixed, but easily distinguishable stereo channels" etc. Then he would encode the test files with JS and try the output. Is it really always exactly L+R or something more irrational? However, the tiny engineer in me would do that only if he really had nothing more important to do.

LOL!

I have a cheap mp3 CD-R player which jumps to mono quite quickly on some files. I never bothered trying to figure out which or why, so Philip Le Riche is a bigger engineer than me already!

Cheers,
David.

Doesn't make much sense to me but anything is possible. Mid / side stereo is a presumed lossless process , so why or how would a player 'detect' this and go into a seizure ?

Which mp3 encoder was used ? does encoding in stereo mode fix it ?

Could this be as simple as a bad connection in the headphone output, causing everything to come out mono? Do normal CDs play properly?

David - I see you're from UK too. Did yours come from Maplin as well, possibly the same Egoman model? You say it reverts to mono on some files ... the disk I was using was a CD/RW - might be worth trying a CD/R. Watch this space...