MP3 distortion problem

[Guest]

I posted this in another section, but this may be the appropriate place for it...

 

This problem is driving me crazy:

 

I've downloaded an mp3 file that has distortion on the high energy passages. At the full chord strums, right at the peaks. Sounds like sparkles or staticy noise. Sounds like it was recorded too hot and the peaks are distorting.

 

The other people involved in the project said they downloaded and played back their copy fine... no distortion.

 

And, I've downloaded another mp3 that the same person created and it's fine.

 

I just have a Soundblaster 16 in my 200 Mhz Pentium MMX PC. I don't use my PC for audio work... I have a Roland VS1680 that I use for that.

 

I wanted to eliminate the sound card, so I burned the mp3 to an audio CD and played it back on another system. The distortion was there too. This would eliminate the sound card, wouldn't it?

 

Can you recommend some software that would let me analyze the mp3 to see if the distortion is "embedded" in there, versus it coming from my system?

 

Also, I guess it is possible I have an outdated codec. I've tried playing this mp3 through Winamp, MusicMatch, Real Player and Media Player with the same results.

 

Here is a link to the mp3, in case you're interested in hearing it. It is a play along or backing track: http://artists.mp3s.com/artists/157/prsforum.html

 

The title is "Another Funk In E"

 

Thanks in advance for any help you can send my way!

 

Mike

[Guest]

Hi Mike,

 

I just downloaded the mp3 and am playing and there is no distortion at all. However, on the last computer I had (a Compaq Presario) I had the same problem as you are having, quite a lot. This machine also had a lot of problems with stereo imaging - 9 times out of 10 the left and right sides would cancel each other out on things like lead vocals that were panned down the center. VERY annoying. Bottom line, is this computer had the worst sound card known to man.

 

Burning an audio CD from your MP3 and playing it on another system would not eliminate the sound card as the culprit, because during the recording process the audio goes through the sound card. The only way to tell would be to just copy the MP3 onto a CD-R (or ZIP disk or whatever) as data and play it back on another computer. I would bet you won't hear the distortion, unless the other computer is just like yours.

 

Also make sure your speakers and speaker cables are OK. I once experienced a lot of pops and static on my computer speakers and discovered that my cat had partially chewed through the cable. It wasn't noticable until I played a music file that had a lot of bass in it.

 

Hope that helps.

--Lee

[Guest]

Thanks for the reply, Lee.

 

I'll followup on the things you've suggested.

 

One thing I want to verify though... are you sure that the soundcard would be involved in burning the mp3 to CD audio? Our guru at work had told me that it would not be in the path... I believe he had burned some on a "scrap" machine at work that didn't have a sound card in it. But, I could be wrong about that. In fact, I'm *probably* wrong about that http://www.musicplayer.com/ubb/smile.gif After all, I'm the guy with the problem, keeping his fingers crossed for a solution.

 

Again, I really appreciate your input.

 

Mike

[Anderton]

It's possible that the MP3 is doing fine in the digital part of the sound card, but distorts in the analog section for some reason (there may even be some hardware problem that is contributing to the distortion).

 

You're probably due for a newer sound card, the Sound Blaster 16 is pretty outdated at this point. I had one several years ago and as I recall, I experienced distortion too. However, with the bar constantly being raised for average signal level (mostly due to lots of compression/limiting), if a sound card was slightly prone to distortion, you may end up with a lot of distortion on music recorded or mastered at a high average level.

 

I strongly recommend getting a digital sound card and putting converters outside of the computer. A DAT machine's converters will work fine. You might want to check out some of the Frontier Design and MIDIMAN/M Audio cards, they're not too expensive and they perform very well.

[Guest]

Thanks for the reply/info Craig.

 

I'll definitely be upgrading the soundcard.

 

Can anyone clarify this for me... if I use a utility to burn an mp3 file to CD, is the sound card "in the loop" or not? Our guru at work swears that he's done this without a sound card in the PC. I don't know enough about it... but I'm really curious about the flow.

 

Mike

 

 

 

[This message has been edited by m.roberts@prodigy.net (edited 09-20-2000).]

[Guest]

I can't answer for certain, as I'm a software guru not hardware http://www.musicplayer.com/ubb/smile.gif, but I believe it can be set up either way and it depends on the individual system and the software being used. That is, you probably CAN set up a computer so that it bypasses the sound card when burning a CD (or so you wouldn't need a sound card at all), but your system may not be that way by default, and if not I don't know what it would take to make it that way.

 

--Lee

[Anderton]

Another consideration...

 

I was just doing some MP3 examples for an article that's about to be posted, and interestingly, some algorithms process the sound differently. For example, Sound Forge did fine encoding to 24 kbps stereo, but in mono, it introduced distortion that may be like what you're talking about. Wavelab, on the other hand, did not introduce this distortion. Furthermore, Sound Forge did not add any distortion in mono with other bit rates I tried.

 

Go figure...I think maybe the problem was that the material being encoded had a rather large boost when going into mono because of commonality of signal in the two channels. Perhaps the algorithm didn't take this into account, and lower the level by 3 dB to compensate.

[THE MIX FIX]

M. Roberts:

 

I believe your "guru" is correct, especially if it is a SCSI CD burner.

 

The digital audio goes directly from the hard drive to the burner, via your burning software, in it's digital form. There is absoultly no need to convert it to an analogue signal during this process.

 

The same holds true for any DATA CDs you may burn, for file backups, for text, photos, software, OR audio files. Why would any DATA have anything to do with a sound card, or have to be convertrd to Analogue? http://www.musicplayer.com/ubb/confused.gif

 

How DOES a JPEG photo sound, being played back, anyway? http://www.musicplayer.com/ubb/rolleyes.gif

 

At least this is the way I have it set up on my system.

 

By the way, don't you REALLY mean the MP3 file in question has MORE distortion at some points, since the whole concept of MP3s is a TOTAL distortion of the signal, to begin with? http://www.musicplayer.com/ubb/tongue.gifhttp://www.musicplayer.com/ubb/biggrin.gif

 

------------------

Bob.

[Guest]

An update:

 

I had the originator of the file burn it to CD and send it to me (redbook).

 

I played it back on a couple of different stereo systems and I didn't hear the distortion... UNTIL I put on headphones. Then, the distortion was audible. But it is subtle. I tried a second set of headphones; same result.

 

I forgot to mention... when I was troubleshooting this problem (working with the VS1680 and my PC), I had headphones on. That may explain why I heard the distortion and other folks did not.

 

In any case, the CD he sent me has the distortion on it, so that eliminated my PC.

 

Thanks for your replies! I appreciate it.

 

Mike

[Uh Clem]

Yep, when I looked at the response of that MP3 File it seemed pretty hot, although I heard no distortion. A little over zealous with the Finalizer or Maximizer plug-ins I think http://www.musicplayer.com/ubb/smile.gif

 

I have noticed if you get to crazy with theze maxmizing tools, even though the digital audio does not clip, a lot of CD players' analog sections cannot deal with maximum levels.

 

If you can get anything to "sound" as loud as RN's last Steely Dan without distorting the analog section of your playback equipment, you have done a trick for sure.

[Guest]

Here is a post from Ariel Pozzo (from the PRS Forum I frequent):

 

Guys

The process of making an .mp3 from a .wav file involves a heavy compression of 11:1, so anything that could be a little hot on the original source will be distorted.

John's mixes tend to be bottom-heavy, but after a little tweaking they sound great.

 

What you should do is convert the .mp3 to .wav format, then open that in Sound Forge or any other editor, and run a spectrum analysis to see the exact frequencies to be attenuated. Once detected, you should use a narrow-Q parametric to tame that freq down by some 6db.

 

The next step would be running a Magneto or Tube Warmth plugin to restore the harmonic content wiped off by the .mp3 compression.

Then you have a restored track. Just run the Smooth-Enhance function to widen the dynamic range, and you're done.

 

Hope this helps.

------------------ www.arielpozzo.com.ar

 

Of course, now I'll need to buy Sound Forge or some other editor... but that was enevitable anyway http://www.musicplayer.com/ubb/smile.gif

 

Mike