FS#6989 - Recording on iPods have weird noise

Attached to Project: Rockbox
Opened by Jason Lyons (bipton) - Saturday, 07 April 2007, 02:02 GMT
Last edited by Peter D'Hoye (petur) - Monday, 04 May 2009, 21:04 GMT
Task Type Bugs
Category Recording
Status Unconfirmed   Reopened
Assigned To No-one
Operating System PortalPlayer-based
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 0%
Votes 0
Private No


I know that the folks that added recording functions to the PP targets only did it as a proof-of-concept, which rteally works well already. I am curious if anyone has looked into the bizarre noise that is generated on the right channel, I have tested this on two different 4g grayscale ipods and on 5.5g ipod. The noise level is lower in the 5.5g than the 4g's. I have attatched a png of jamin running a "silent" recording (no mic connected) and the wavpack file. I amplified the sound to get it to register higher on my spectrum analyzer.
This task depends upon

Comment by Jason Lyons (bipton) - Saturday, 07 April 2007, 02:52 GMT
Huh the wv file didn't upload
Comment by Jason Lyons (bipton) - Saturday, 07 April 2007, 16:25 GMT
Here's a couple pictures from baudline one is a clean wav file (no sound) the other is from the above sound file, it seems the noise is all over the frequencies. Here's a link to baudline for the curious
Comment by Peter D'Hoye (petur) - Tuesday, 19 August 2008, 21:20 GMT
This does not seem to be pp5020 related because my H10 doesn't do this. Either this has been fixed or is ipod specific.
Comment by Peter D'Hoye (petur) - Monday, 04 May 2009, 21:06 GMT
reopened as requested by Jason Lyons:

"I opened the task april 7th 2007, I have gone through a number of
players since then and am now back to using an 80gb ipod video. I tried
recording again on this unit using the latest stable build and the
bleeding edge build. The same EXACT noise that existed 2 years ago on my
4th gens, and 30gb 5.5g ipods is still existent on this unit also.

Comment by Jason Lyons (bipton) - Wednesday, 06 May 2009, 03:26 GMT
To reproduce, turn on your player (ipod), start should see one of your peak meters bouncing on the bottom. You don't need anything plugged it, just record.
Comment by Jeff Tanner (jtanner) - Saturday, 06 June 2009, 03:53 GMT
Mine does the same thing. I have a 5.5gen video & just like you, when you start up the recording app, you can see the right channel monitor level jumping. And when you listen to the recording afterward, you can hear the "noise" in the right channel only. The left channel is crystal clear. I hope someone can fix this issue as I would love to be able to use my ipod to record some high quality audio without this noise.
Comment by Billy (ipodfoo) - Friday, 12 June 2009, 20:30 GMT
Ive attached a screenshot of the spectral analysis in Audition of a 5 second recording on the iPod Nano set at 0dB gain. Ive lightened it up in Photoshop. Blips on the dB meter seems to occur when playing it back at the large "waveform" bit. The dB meter doesnt go higher than -70dB. It seems to be on the left channel. The right is clear.

It looks like semi-regular noise blips. Hope that helps someone in debugging.
Comment by Billy (ipodfoo) - Friday, 12 June 2009, 20:34 GMT
Forgot to mention, I was purely recording silence with nothing plugged into the dock.
Comment by Billy (ipodfoo) - Friday, 12 June 2009, 20:57 GMT
Also, this was recorded with Rockbox 3.2 March 23, 2009. and here's the wav file. :)
Comment by Billy (ipodfoo) - Friday, 12 June 2009, 21:00 GMT
Cut down file to allow uploading.
Comment by David Hall (Soap) - Monday, 15 June 2009, 12:32 GMT Comment by Billy (ipodfoo) - Monday, 15 June 2009, 21:22 GMT
>Is this related to ?

Ah yes, that looks more like my problem thanks! I'll do a little more testing but I'm pretty sure the blips correlate with the clickwheel.