iPod Decoder Problems

2002-12-09 17:01:28

Hi,

I have a new iPod and have noticed the following problems:-

1.  Sibilance / Graining in vocals
2. Crackling / Popping distortion on long notes.

Number 1. Occurs quite frequently using iTunes Encoder and Lame 3.90.2 in any configuration.

Number 2. Occurs now and again on long notes example a long sustaining electric guitar note on Garry Moore's Ballads & Blues song "Parisienne Walkways" as the note is played after about 5 secs it will start to break up into distortion, but if it is played on my iBook (iTunes) or PC (Winamp) there is no distortion on the MP3 file!

I have tried iTunes 3.01 encoder (All options) & Lame 3.90.2 all Presets inc ABR/CBR/VBR and still have this distortion, I have also tried MP3Gain and normalizing the WAV file.

Then, I tried Bladeenc -256 and guess what no distortion the file played perfectly!!!!

Could anyone shed any light? What is Bladeenc doing differently and why is the iPod decoder struggling with Lame/iTunes files?

Colin

iPod Decoder Problems

Reply #1 – 2002-12-09 18:53:05

Hi,

Sad to hear that...

- Have you tried LAME-encoding with --strictly-enforce-iso ?
- Have you tried contacting Apple ?

Cheers

iPod Decoder Problems

Reply #2 – 2002-12-09 19:37:24

Thanks for the reply!

I have tried --strictly-enforce-iso  and still have the same problems.

Colin

iPod Decoder Problems

Reply #3 – 2002-12-09 21:50:16

I would consider this a bug in the iPod, then. Check if there are any firmware updates; if not, file a bug report.
Or maybe your specific iPod is at fault? Can you try it with another one?
And "--strictly-enforce-iso" is not really an option here, cause it defies the porpose of using LAME for high quality...

iPod Decoder Problems

Reply #4 – 2002-12-10 03:14:30

Ramdrive,

  About six and a half months ago I bought my bride-to-be an iPod for her wedding-day present (ours is a mixed marriage; she's a self-proclaimed "Mac snob," and I am a contented Windows XP user). I encode her music via Lame 3.90.2/Speek's frontend with "No Gap" turned on, and using the following switches: --alt-preset CBR 192

  Her iPod firmware is version 1.1 - there has been a 1.2 update, but we haven't bothered to upgrade to it yet - and we have never encountered any of the problems you described.

  Sounds like you got a defective unit... which, if so, should be under warranty. Give Apple a call; they've always been good about respecting their service agreements, from our experience.

    - M.

iPod Decoder Problems

Reply #5 – 2002-12-10 12:51:10

M,

I am using 1.2.1.

I will post the 10sec problem clip in Blade & Lame (CBR 192)  formats, it would be great if you could give them a try on your Pod and let me know what you hear.

Maybe I need to downgrade to 1.1 

Cheers

Colin

iPod Decoder Problems

Reply #6 – 2002-12-11 19:58:03

Here is the 30 second clip in MP3 & WAV formats:-

The original WAV file (5MB):-

http://homepage.ntlworld.com/colinwalker/wav.zip


The MP3 version processed with Lame 3.93.1 with the "--alt-preset standard" command line:-

http://homepage.ntlworld.com/colinwalker/mp3.zip


As you will see the mp3 will play fine on a PC but on the iPod you get loads of cracking popping sounds at around 15 seconds into the tune.

Please test on your iPods and let me know what you find.

Colin

iPod Decoder Problems

Reply #7 – 2002-12-12 03:53:31

Okay, after a quick test here are my impressions:

  This is a live recording; therefore there are/will be audience noises. Around 15 seconds into the sample, the audience begins applauding. Now, knowing there is applause it's fairly easy to allow for that "noise" coming through a decent set of speakers. After all, it's part of the concert experience. However, when listening through earphones the impression was not so much one of applause, but of "crackling." Other than that, the iPod has no difficulty with the sample... it plays fine.

  Now, a couple of simpe questions. You've probably already thought of these, but I'm also trying to cover anything that might have been so obvious it got overlooked. 

  1) Does the audience applaud every time this performer goes into a sustained note on his guitar?
  2) Could your listening environment/equipment have anything to do with the "Crackling / Popping distortion" you described?

  You said your MP3 sample was encoded with L.A.M.E. 3.93.1, but that version is not currently recommended with "--alt-preset"; I doubt this could have any serious affect on an iPod's performance, but for now you might want to stick with 3.90.2 for iPod encoding.

  Also, you mentioned "Sibilance / Graining in vocals," but since the sample you provided contained no vocals I couldn't really evaluate this....

    - M.