Hey Guys and Gals,

I've been struggling with my player's inability to play low-bitrate encoded files for a while. I record tons of radio and spoken word stuff in mp3 format so I can listen to it in the car, but unless I record at least at 32k, it is unlistenable. On the PC, I can playback as low as 8k files with no quality problem at all. But these same files sound like hell in the car (bad scrambled flanged jittery playback).

I know the empeg has problems with low bitrate files, but is there any way to fix this? Four hours of audio at 8k is like 20 megs, versus 70 or 80 at 32k, so I'd much prefer the lower setting...

Stumped! I've attached a sample file; try it out! It is at 16k, sounds fine in winamp, unlistenable in the car.

Skeeter

You could upsample them for the player. Dump them to WAV, then re-encode them at a higher bitrate. You won't increase the quality of the files (in fact, you will decrease the quality very slightly), but at least they'll play correctly.

Keep in mind that it's unlikely to be the bitrate that's the problem. More likely, it's the samplerate or bit depth that's the problem. For instance, the player shouldn't have any trouble playing back a 44khz 16-bit stereo file even at painfully low encoded bitrates. However, if you try to play a 8khz or 11khz mono file, regardless of how well-encoded it is, then it's got to do samplerate conversion on-the-fly up to 44khz 16-bit before it can play back the audio. The player's samplerate converter probably just isn't as well-optimized as the one on your PC.

The trick is, when you dump your low-samplerate files to WAV, you have to make sure to do it into 44kz 16-bit stereo with something that does a good job of samplerate conversion. Perhaps TotalRecorder can help in this situation?

Yeah, I just record them at a higher bitrate and samplerate now... Not an ideal solution, though. Smaller files slow the player down less, take up less space, transfer more quickly, etc. Guess this is just a limitation of the player. Is there any hope of this being solved in future releases? Is it a hardware or software limitation?

I just need to be more dilligent about clearing them off after I've listened to them, and maybe I should get off my butt an slap in a bigger drive or two

Thanks, you the man,

Skeeter

Is it a hardware or software limitation?

Technically, it's both.

Hardware: The DSP, if I recall correctly, can only play 44.1khz 16-bit stereo. I think this is because it's originally intended for use in car CD players.

Software: Because the software has to upsample anything to 44/16/stereo, it's got to go through a samplerate converter. Doing samplerate conversion is a bit of a black art as far as software is concerned, it's not as simple as just padding the values. There's some actual math involved.

Although I think it might be possible to improve the samplerate converter in the software, I'm not certain if it's a CPU-limitation, or just a lack of good source art for that kind of thing. If I recall correctly, the really GOOD samplerate converters are patented.