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Using OTG USB for audio out?
#1
I have an IK Multimedia Irig Pro Duo, that I connect via the OTG USB connector. The Pro Duo is powered up so I knwo the cable is working, however when I play an audio file in MSP, the audio still comes out the android device headphone jack and NOT the Duo.

I have asked at the IK forum and got this reply:
The app would need to support using a digital connection audio interface (via USB OTG) in order to output via iRig Pro Duo. Typical listening apps are not likely built with such support, but audio recording/performance apps would be more likely to support audio interfaces for input and output.

Is there any way to force MSP to use the OTG USB as the audio out?

Thanks
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#2
What device are you currently using and what OS version is it running? Google added USB audio support to the OS starting in Android 5.1. That's why I haven't tried to add support for USB audio out. The OS supports it for the majority of devices, and it would be incredibly complicated for me to try to support it with my own code.

Mike
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#3
Using the HP Pro slate 12 Mike. OS 5.1.1 (which IS the final and only as HP have 100% dropped all support for HP Tablets, AND they refuse to allow the bootloader to be unlocked so users cannot load 3rd part ROMs). OK understand. I sorta thought it would be too tough to implement. I only asked as you recently were able to change the player used, so I thought maybe this step would be an adjunct to that.

Not to worry. I think I will have to revert to an iPad Sad the pops and clicks from this HP headphone jack are not at all good. Hence my getting the iRig - I thought that maybe if the audio comes out the USB port it may stop it.

Thanks

PS: Seems I am stuck with a $500 brick! It still runs so it is not "bricked" but it is useless and because of the dropping of support virtually unsellable! Oh I could sell it for $50 but after having paid $540 for it 6 months ago, that is quite a drop!
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#4
So I read the Google article here (https://source.android.com/devices/audio/usb.html) on USB audio, and I don't know why your device wouldn't be routing the audio to your DAC. Your device should be in host mode though, and the audio should fit these parameters:

Android 5.0 (API level 21) and above supports a subset of USB audio class 1 (UAC1) features:

The Android device must act as host
The audio format must be PCM (interface type I)
The bit depth must be 16-bits, 24-bits, or 32-bits where 24 bits of useful audio data are left-justified within the most significant bits of the 32-bit word
The sample rate must be either 48, 44.1, 32, 24, 22.05, 16, 12, 11.025, or 8 kHz
The channel count must be 1 (mono) or 2 (stereo)

And further below:

Typical USB host mode audio applications include:

music listening
telephony
instant messaging and voice chat
recording
For all of these applications, Android detects a compatible USB digital audio peripheral, and automatically routes audio playback and capture appropriately, based on the audio policy rules. Stereo content is played on the first two channels of the peripheral.

There are no APIs specific to USB digital audio. For advanced usage, the automatic routing may interfere with applications that are USB-aware.


So according to that, MobileSheetsPro shouldn't have to do anything at all for the audio routing to occur. In fact, if i did try to do something, the automatic routing could interfere with my processing. I think you should focus on trying to see if we can get the USB audio out to work before you completely give up on it.
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#5
If you go under the developer options in the settings on your device, there is an option where you can pick the USB Configuration. One of the options is Audio Source. Did you try selecting that?
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#6
Thanks for all of that Mike - it was pretty much similar to what I have read myself. I will give it another go...especially as the Pro actually "sees" and powers the iRig - haha the iPad doesn't! IIRC I did check that under developer ops, but maybe worth a try again, in case the "swipe" didn't quite take and I backed out of the options page too quickly..

Will let you know Smile

PS: You also need to have the iRig connected before powering up the tablet, and again, I'm reasonably certain I did this, but I will check again.
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#7
Well I just tried it all again, MP3s still play via tablet speaker or headphone jack, NOT out the iRig uisng MSP. Mp3s DO play out the iRig when using VLC Player. BTW on the HP the only USB Audio option is to enable/disable USB Audio. None to specifically choose USB for Audio.

EDIT: just retried VLC (it DEFINITELY worked yesterday) and it too has defaulted back to using the tablet speaker/headphone jack. I am now starting to think there are issues with this HP device!
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#8
Well, It IS possible to unlock the bootloader, if you are brave enough!

You could even install a Nougat ROM if you like.

http://unlock-bootloader-android.org/tut...-slate-12/

If the market value is really near zero, you have little to loose, and a LOT to gain.

I'm not a rooting expert, so proceed at your own peril.
I have read that it is really near impossible to actually 'brick' and Android device.
I could be wrong, it happened once before.
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#9
ahhh, no. It is not. Follow the links Wink That is a feeder page to entering all these surveys, and then trialling other stuff, before you get anywere NEAR data. And there are about 20 other Google hits that led back to the exact same pages. It is a scam with no actual result at the end. Go ahead try it Smile

And the HP Pro Slate series have the bootloader permanently locked in teh firmware by HP. It needs a HP firmware update to change this! Believe me I have been harrassing them constantly about it, absolute silence from their end hahaha, but one keeps trying!

For the record I CAN root this device ad have done so. But rooting is only a small part of the story. The bootloader is where all these 3rd party roms get loaded from. Locked bootloader means all you can load is a ROM that is exactly the same version of Android that is installed. For example I have installed the gAPPS PICO rom - BUT it is still 5.1.1. with very primitive USB support. I am thinking Marshmallow or Nougat might be a bit more mature, however they can't be loaded...because??? Yep a locked bootloader!
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#10
If you are seeing unreliable behavior with the USB audio out and it doesn't seem to be working at all with MobileSheetsPro, then unfortunately, I'm out of ideas Sad I wish I could quickly add support for USB audio out, but it would only be possible if I already had my own low level audio engine implemented. I'm using Google's library for doing all of the audio playback, so there is no control over how the audio is routed.

I was looking at this thread https://community.spotify.com/t5/Android...d-p/874571 and saw a user post the following:

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

After few tries I finally got it worked on my HTC M8 with Nexum Aqua USB DAC/Amp.

Try these steps and see if you got any luck:
1. unplug the external DAC (Nexum Aqua in my case) from the device (HTC M8 in my case)
2. start playing music in Spotify; music will come out from device's loudspeaker.
3. set Spotify/device volume to mid or low level to avoid sudden burst later on.
4. plug in earphone to the external DAC, and then plug in the DAC to the device while Spotify is still playing.
5. Wait for few seconds, and then music output will switch from device loudspeaker to earphone via DAC.

The steps has to be repeated again everytime when switching the music player from Spotify to others (such as Android default Music Player) and back to Spotify again.

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

I wonder if the same steps might work for MobileSheetsPro...
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#11
Thanks Mike - plase don't misunderstand me, it si NOT the fault of MSP or anything you have not done or are planning on doing.

It is
1. The half-baked USB audio implementation of thr Android OS 5.x and 2. HPs bloodymindedness re locking the bootloader

I'll have a go at trying those steps you wrote....I'll let you know Smile
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#12
Interesting...when I connect the iRig I get a message popping up>>>>Open MobileSheetsPro when this USB device is connected, then if I press OK, it re-boots the tablet !!?? Alternatively it then pops up a box saying use MSP as the default for this device. However in either case it still does not work. The method also doesn't work when using the HP player or VLC player Sad I wonder what Android version that poster was using. I might visit the link you posted and see if I can pick up some tangental clues haha!
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#13
Well, following that thread I discoverd and app called USB Audio Player Pro, and it works!! No clicks or pops...just simpy works! So that proves that perhaps USB Audio is ok in 5.1.1 USB Audio Playre Pro , I note, has its own built in USB DAC drivers. This indeed may be the key. Sadly it does not seem to work with a bluetooth pedal for starting of songs.

As MSP won't be able to access the app to play songs, I was thinking of using my Nexus 7 to run the audio side of things and use MSP only for the charts. Yes a secondary device and MUCH more awkward to link audo files (well no link at all really, just a matching songlist haha) which is fine I guess for static playlists, but will make it annoying for dynamic changes...

anyhoo, USB audio works as long as you have an app with DAC drivers, and don't rely on Android OS drivers.
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#14
I wouldn't recommend associating MobileSheetsPro with the USB DAC like that. MobileSheetsPro is trying to connect to it as a MIDI device over USB, which obviously won't work.

I wish there was an open source library for handling USB audio or even one that could be licensed, but there doesn't seem to be anything like that out there. I guess if I ever find lots of time, I could work on writing my own, but it seems like it would be a pretty large undertaking.

Mike
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#15
Absolutely Mike - way too big a job with all the other development work you are continuing on with re MSP! - maybe try contacting the developers of USB audio Player Pro, and see if they'd be prepared to licence its use for MSP??
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