recording on Ipod Video using MicroMemo

[willemmerson]

Hello, I am trying to record with rockbox using an XtremeMac Micromemo and it isn't working but it should do according to this http://www.rockbox.org/twiki/bin/view/Main/IpodAccessories.
What am I doing wrong? I have tried both line and mic as source but neither is working.

[Chronon]

The mic setting won't be of much use to you.  

What happens when you record?  Does it produce a recording of silence?  Do the peak levels change on the recording screen?

[benbojangles]

Hi,

I'm new here. But after coming across this forum, I thought I must contribute!

I'm currently experimenting with my Ipod 5g, Micromemo adapter, and rockbox, as a field recorder.

I can confirm that I can record using the 'line-in switch' on the micromemo. However, I am getting a 'pulsing hiss' on the right channel when recording stereo.

I'm just wondering if anyone else has experience using rockbox with an ipod &micromemo recorder? Because, I get hiss in the right channel when recording with rockbox, but not with the standard ipod recording application. It has to be rockbox, right???

If I could just get this hiss sorted out, i'd have a brilliant recorder. Anyone any ideas???

You can read about my adventure, and listen to the 'pulsing hiss' sound here:
http://dalybulge.blogspot.com/

I also noticed that there is a bug report on the tracker & bug page:
FS#6989 - Recording on iPods have weird noise

Any questions or ideas & tests you would like me to do?

Thanks. B

[Chronon]

Welcome!

I don't think too many people have reported about using this with Rockbox.  There have been some changes to Rockbox since last year, such as some preliminary support for the Apple accessory protocol.  You will notice that the Micromemo is listed as a device that needs retesting on the IpodAccessories page that was linked earlier.  A good first step would be to update that -- indicate whether volume control works now, etc. 

Yes, that Flyspray task sounds like the bug you described.  You say that the sound pulses?  I wonder if any features of the pulsing carry clues as to the source of the noise.

[benbojangles]

Not sure what the Apple Accessory Protocol includes entirely. However:

- the volume control on Rockbox works with Micromemo
- gain control works; if a bit temperamentally: If you play with the gain too much/too rapidly, it can lose the sound input altogether.

-The 'pulsing Hiss' in the right channel is there on the rockbox meter bar. A small signal (about 2-9% of the meter bar total).
-It is there, with, or without a micromemo plugged into the 5g ipod 30gb on record mode.
-It's there with, or without the screen backlight
-It's there with or without the sound of the HD spinning.
-it's there regardless of the recording format you use
- or, if you use 'Line-in' or 'Microphone' as the source setting on Rockbox. (Not that Microphone does anything on the 5g, right?)

There's something weird going on.....

The standard Apple Ipod memo-recording utility works without the hiss.

So, it can't be hardware electrical interference, can it? Am I right in assuming that Apple firmware runs from flash memory, and the rockbox runs from the Hard Drive? - Maybe it's time to crack it open and wrap the HD in insulation tape.

I'm just trying to figure out the differences between Apple & Rockbox, in the way they run. Once that's ruled out, then maybe examine Rockbox's code.

*Also as an update to the Micromemo IpodAccesories chart: The little output speaker on the micromemo doesn't function with rockbox (Or, at least I can't figure out how to get it to function) - But rockbox pumps out audio with my big speaker dock.
-Also, as the previous tester described: volume adjust doesn't have any use on rockbox, when using accessories (tested with micromemo & iwantIT iw500 ipod speaker dock), but, neither does Apple's Firmware.

Micromemo model code: XM# 11020703 or: XRD06VMIC01USBK 

[Chronon]

Both the Apple firmware and Rockbox run from the HD. 

[Llorean]

Well, really, both of them run from RAM. Rockbox is loaded into RAM when you boot up the player, and when you're in the menus shouldn't really access the disk at all.

When you browse the files, play music, or record though, the disk will be accessed. Both the Apple firmware and Rockbox have to write your recording to the disk from time to time because there's only so much RAM in the player.

[Chronon]

Thanks, Llorean.  That was a bit sloppy of me.   

[Llorean]

It is true, though, that they're both loaded from the HD at boot.

[benbojangles]

So, both Apple's Firmware & Rockbox run pretty much in the same way (from RAM), and use the disk during playback & Recording.

So, I can rule that out being the problem (probably).

So, I guess, it could be the ipod dock connection that isn't configured for rockbox correctly

- perhaps different pins are being used for the right channel input on Rockbox, than for the right channel on Apple's firmware?

- or, perhaps, Apple's firmware turns off some pins when recording is enabled, and Rockbox, maybe leaves them turned on, by accident? : (This may be a question for the Apple AccessoryProtocol experts.)

- Is there a diagram or photo showing which-pins-do-what on the 5g Ipod connector? And then comparing them to the Rockbox's?

We've ruled out hardware error on the micromemo. Because, the hiss is always there on record mode no matter what is connected or not.

Progress so far:

Is that the record function works on Rockbox, on both channels. However, right channel has the 'pulsing hiss' due to rockbox leaving some pins running, when they should be off. My money is on that. 

*I've been thinking:
The Apple firmware does not allow you to 'live-monitor' during recording, but Rockbox does. This is the most obvious difference between the Rockbox's 'hiss' recording, and Apple's 'no-hiss' recording. I'm guessing Apple turns off the headphone jack when memo-record is activated.

-Could it be that Apple did this deliberately, after discovering the same hiss during product testing?
-And, then cut the headphone jack as a fast solution just before releasing the product?

-Is there a way to turn off the headphone jack completely using rockbox? I don't mean just turn the volume right down.

It could be that the problem 'pulsing hiss' is caused by a hardware design conflict between the headphone-out, and the Line-in (right channel) on the ipod connector...

[Chronon]

The Apple accessory protocol just involves serial communication.  The noise problem in the right channel happens regardless of any attached accessory attempting to communicate via serial.

For the pin assignment, see: http://ipodlinux.org/wiki/Dock_Connector

[benbojangles]

How about being able to disable the headphone jack using Rockbox?

It would be one more possibility eliminated.