Author Topic: Getting signals into the iPhone [UPDATED June 9, 2009]  (Read 24582 times)

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FaberAST

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Getting signals into the iPhone [UPDATED June 9, 2009]
« on: July 11, 2008, 11:13:06 AM »
Update, June 9, 2009: The latest audio input/output information, for iPhone and iPod touch devices, is now available on the blog.

This topic addresses several questions that have been coming in regarding SignalScope on the iPhone.

There are basically four ways to get signals into SignalScope on iPhone:
  • Built-in Microphone. When using the built-in microphone, the sample rate is limited to 8 kHz, so you only get about a 4 kHz bandwidth.
    Update, July 29, 2008: The iPhone 3G can sample the built-in mic at 48 kHz, so the 8 kHz sample rate limitation only applies to first-generation iPhones.
  • Headset Microphone. With the headset mic, the sample rate will jump up to 48 kHz. I don't know how flat the mic response is, but even inexpensive electret microphones can exhibit a remarkably flat response. I have measured frequencies over 20 kHz in SignalScope with the iPhone's headset mic.
  • Headset Input. The headset input allows for a single channel of audio band data. If you want to use anything other than a headset mic, you'll need an adapter cable. A standard mini-plug (1/8-inch) to RCA A/V cable should work (that's a four-conductor mini-plug on one end and three RCA plugs on the other). The recessed jack on the original iPhone may require another adapter, or modification of the A/V cable. I haven't really nailed down the acceptable voltage range, although the input seems to be expecting a low-level mic signal, so input signals may need to be attenuated before they get to the iPhone. A Type 1 measurement microphone (50 mV/Pa), with a unity gain preamp, seemed to clip the iPhone input very easily (with relatively low sound levels).
  • Accelerometer. In SignalScope, the accelerometer is sampled at 100 Hz and currently supports units of "g" (that's gravity, not grams). I don't know how accurate the calibration is--it was calibrated by the manufacturer.

Notes:
  • SignalScope currently does not support (sensitivity) calibration of the audio input, or audio signal units other than %FS (percent of full-scale, or clipping, voltage)--SignalScope Pro does.

Ben
« Last Edit: July 08, 2009, 11:29:13 AM by FaberAST »

jnugent7bb

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Re: Getting signals into the iPhone
« Reply #1 on: July 14, 2008, 07:09:10 PM »
First off, I want to say that software is awesome, thank you very much. Now this is just an idea, you could call this a helpful suggestion. The iphone has really clean audio connections from what I have experienced, but apple has a cable which may work better than using the headphone jack. Now maybe this won't work, and I don't know if you really want to do it, but there is a 30 pin connector that you can plug into the iphone. The one I had was made to cover every input channel to the DVD player HD, and then connect the 30-pin to the iphone. http://store.apple.com/us/product/MB129LL/A?fnode=home/shop_ipod/ipod_accessories/cables_docks&mco=NTQ4OTg That cable is a composite standard A/V cable, that probably could work for what you are wanting to do for input. That could also have the cable from the from the computer for a power source/possible input, into the 30-pin connection line pre-composite hook in. http://store.apple.com/us/product/MB128LL/A?fnode=home/shop_ipod/ipod_accessories/cables_docks&mco=MTM1MTc Now that is the one I have, now maybe you could find something to do with the extra (Pb, and Pr), possibly, I am not sure, I should read up on it, but, maybe that Pb and Pr line could hook into the iphone with the composite sources. Then this could have 2 devices going in at once. I really don't think that is necessary, but hey it is a idea. Maybe that would be useful for a multi channel surround sound setup. I was thinking that the 30-pin connection would provide clean audio to the iphone, vs's a headphone jack. I know I would love the idea of having the option to save a print out/screenshot while measuring an audio level. If you are already at a computer you could just hook it up through another interface though.... All of this maybe unnecessary because you had said you don't know how to hook up through the doc connector, I am not sure if that is a software compatibility issue or if you just did not know how that there was 30-pin A/V cable for the iphone.

Once again, thank you very much for the software, it is a gift to us OCD techie aficionados.

Oh one more thing, I am going to test the 30-pin connector anyways, if it works I will let you know. I bet you were testing it previous to putting it on the market, I will give it a shot though.
« Last Edit: July 14, 2008, 07:12:47 PM by jnugent7bb »

FaberAST

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Re: Getting signals into the iPhone
« Reply #2 on: July 15, 2008, 09:02:35 AM »
jnugent7bb,

I'm glad you like the software.

Currently, the only supported methods for getting audio data into the iPhone are using the built-in mic, or routing audio through the headset jack. Devices that use the dock connector for audio input (Belkin TuneTalk Stereo, Griffin iTalk Pro, etc), aren't currently supported by the iPhone OS. We have submitted a request to Apple for this type of support, and it sounds like others have, as well.

Regarding screenshots, you can tap the camera icon in SignalScope to capture the current analyzer display, even while it is running. Also, in any app, you can hold down the power button and press the home key to capture a screenshot. In either case, the image is saved to the iPhone's Camera Roll photo album.

Ben

timtec

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Re: Getting signals into the iPhone [UPDATED]
« Reply #3 on: December 10, 2008, 10:48:44 AM »
Since the release of 2.2 which supposedly allows the use of line in, are there any devices that work?

FaberAST

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Re: Getting signals into the iPhone [UPDATED]
« Reply #4 on: December 10, 2008, 11:35:40 AM »
With iPhone OS 2.2, it appears that the Belkin TuneTalk Stereo works with the iPhone, iPhone 3G, and iPod touch 2G. The Griffin iTalk Pro works with the iPhone 3G. Neither device works with the original iPod touch.

timtec

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Re: Getting signals into the iPhone [UPDATED]
« Reply #5 on: December 10, 2008, 08:04:48 PM »
I have the ITalk Pro and it doesn't work with my 3g any certain software I need to make it work?

Riley Casey

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Re: Getting signals into the iPhone [UPDATED]
« Reply #6 on: February 11, 2009, 11:58:44 AM »
I have recently acquired an ipod touch 2G with audio input.  I want to get signal into via the mini jack. I've seen TRRS mini to three RCA cables in the wild and thought that Radio Shack at the very least stocked them but apparently not. Does anyone know who stocks these ? It would be a pain to have to just buy the iphone headset and cut that up.

Also while we're on the subject.  Has anyone built a pad for this application and if so do you know what attenuation is required to bring a line level signal down to match the sensitivity of the iPod touchs' input?

Riley Casey

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Re: Getting signals into the iPhone [UPDATED]
« Reply #7 on: February 20, 2009, 12:20:54 PM »
I have acquired several TRRS style mine to RCA patch cables which as it turns out are called AV camera cables.  I have identified the appropriate contacts for what should be signal input to the Ipod touch ( Ring 2 and sleeve counting from the tip with Ring 2 being the common for all inputs and outputs ).  Signal Suite shows a " no input display " on the screen.  I can measure signal at the mini plug prior to mating with the Ipod touch.  Is there anything in Signal Suite or the Touch that I need to enable software wise to make Signal Suite look to the mini jack for input ?

polarbreeze

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Re: Getting signals into the iPhone [UPDATED]
« Reply #8 on: July 08, 2009, 10:44:52 AM »
With iPhone OS 2.2, it appears that the Belkin TuneTalk Stereo works with the iPhone, iPhone 3G, and iPod touch 2G. The Griffin iTalk Pro works with the iPhone 3G. Neither device works with the original iPod touch.
Hi, you mentioned "it appears" but could you please confirm whether the Belkin TuneTalk Stereo does officially work now with the iPhone 3G (OS 3.0) and now, hopefully the 3GS too. Many thanks, there does seem to be a bit of confusion out there and it would be nice to hear form a real live app maker about this!

FaberAST

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Re: Getting signals into the iPhone [UPDATED June 9, 2009]
« Reply #9 on: July 08, 2009, 11:26:37 AM »
Quote
could you please confirm whether the Belkin TuneTalk Stereo does officially work now with the iPhone 3G (OS 3.0) and now, hopefully the 3GS too. Many thanks, there does seem to be a bit of confusion out there and it would be nice to hear form a real live app maker about this!
Yep. Take a look at the articles recently posted on the blog, particularly the one regarding dock connector I/O compatibility. Devices that work with the iPhone 3G also work with the iPhone 3GS.

Ben

Audiofile

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Re: Getting signals into the iPhone [UPDATED June 9, 2009]
« Reply #10 on: October 09, 2009, 01:20:12 PM »
Is there currently any Faber Acoustical product that can function as a dual channel scope on an iPhone? If I am understanding this thread correctly, the answer is no. And the main reason is that Apple does not currently support accessing stereo audio input with its SDK.

Can you confirm, or clarify what the facts are if I am mistaken?

Thanks!

FaberAST

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Re: Getting signals into the iPhone [UPDATED June 9, 2009]
« Reply #11 on: October 09, 2009, 01:31:52 PM »
Audiofile,

SignalScope, SignalScope Pro, and IOScope can all work with two-channel audio input via third party accessories connected to the dock connector.

The following articles (on the blog) may be of interest to you:
Dock Connector Audio I/O
iPhone Line Input Frequency Response Comparison

Ben