Does anyone have any idea how to make the sound output on a mac or PC only at 432Hz instead of 440Hz? Are there any SDKs or opensource frameworks that could enable this?
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I am building a Bluetooth audio receiver as an embedded system with the CHIP sbc (single board computer) from getchip.com. Pretty similar to Raspberry Pi, runs Debian Jessie, too.
I am using the onboard 3.5mm jack as an audio output. I configured PulseAudio to receive the Bluetooth audio and redirect it to the ALSA sound driver.
Everything works flawlessly except for static noise on the output.
Directly after boot there is a medium loud sum in the few hundred Hz region.
It´s always in the background, even if I play something via bluetooth or locally via CLI.
The interesting part is that it disappears after exactly 10min and 10sec after powerup, so I think exactly 10min after the startup of PulseAudio or ALSA.
I couldn´t find a reason for it.
I tried the tsched=0 fix in /etc/pulse/system.pa
I unloaded the module suspend-on-idle in /etc/pulse/system.pa
And by the way, I´m running PulseAudio in system-mode, as I´m using it as an embedded system and not a multi-user configuration. I hope I get help from you anyway ;-)
Maybe you have an idea where this noise could come from?
It has to be some sort of software configuration issue, otherwise it wouldn´t disappear after exactly 10mins.
I´ll add the PulseAudio and ALSA configuration files later this day.
Thanks in advance!
Fortunately I solved the problem on my own:
The C.H.I.P. from NextThing has a 3.5mm TRRS jack, which does not only output stereo audio but component video as well.
Now if you plug in a standard 3.5mm jack, the ground pin does does interfere with the component video connector.
Thats why there was this humming noise on the audio output. And thats why it disappeared exactly after 10mins, because the screen idle time is 10min, I think.
So I have to admit, that it was indeed not a programming question as it was a connection issue. Thanks anyway for the quick answer!
I am to test voice recognition programs. Some which I have access to the code and others where I don't.
Sadly my (beautiful) voice is not perfect, so when I am reading a text it sounds slightly different each time. Which makes the testing difficult and time consuming. Giving that I can tweak a lot of parameters.
So I was wondering if there was a way to record my own voice (already done). And then play it as normal microphone input so the voice recognition program I am testing will see it as microphone input.
This would also help greatly if it could be done programatically in C#. So I can in my own code specify when to play what.
To play it from speakers and have the voice recognition programs listen to the microphone is not an option, because it is not the same sound on different computers/speakers/microphones.
Thanks.
Edit:
What i have found so far is to use a software sound Card simulator. But I haven't been able to find a suitable one.
Just as there are printer drivers that do not connect to a printer at all but rather write to a PDF file, analogously there are virtual audio drivers available that do not connect to a physical microphone at all but can pipe input from other sources such as files or other programs.
I hope I'm not breaking any rules by recommending free/donation software, but VB-Audio Virtual Cable should let you create a pair of virtual input and output audio devices. Then you could play an MP3 into the virtual output device and then set the virtual input device as your "microphone". In theory I think that should work.
If all else fails, you could always roll your own virtual audio driver. Microsoft provides some sample code but unfortunately it is not applicable to the older Windows XP audio model. There is probably sample code available for XP too.
I want to add a function to my App, where the user can choose to play the audio on a bluetooth enabled speaker. I have a Parrot Easydrive in my car and this works for phonecalls and for example the Dictafoon App among others.
I understand that I should use the Core Audio framework. WHen a bluetooth device is connected it is said that it is easy to stream the audio to that connection. I am now looking for Core Audio sample code (or a book) where connecting and streaming to a bluetooth device with Core Audio is explained.
Can anyone shed a light on this? If there is another framework or sample code which I can use please mention it!
Many thanks in advance!
You don't write any specific Core Audio code, it is the same process as is used to play audio via AirPlay.
Basically you put a MPVolumeView into your UI, and the underlying framework will redirect your audio output for you. Once you implement this you will be able to use Bluetooth and any AirPlay enabled device with your app.
I'm looking for documentation on how to build an ADC Core Audio compliant to connect to a mac USB or Firewire. All I've been finding is info on how to deal with Core audio on programing the computer side.
I need info on how to make audio hardware Core Audio compliant.
Can anyone send me the right direction?
This a nice solution. It does all the hard work for you. If you have even basic hardware engineering experience this should get you on your way. This chip will work great. Very few external components needed.
http://www.silabs.com/products/interface/usbtouart/Pages/usb-to-i2s-digital-audio-bridge.aspx
I have an application in an embedded system that has a application which is OSS based. Unfortunately, this application is at a fixed sample rate (8K), but I need it to be at 48K. Furthermore, I can't change the application.
I'm researching sample rate conversion plugins, such as dmix or libsamplerate, but I don't see how to use that with OSS.
Can somebody please point me in the right direction? Can I configure ALSA in such a way as to convert the OSS interface from 8K->48K in/out of the system?
TIA
Mike
What you want is the alsa-oss package which provides a tool you can use to run a program and redirect it's OSS sound output into ALSA where all the normal ALSA tools are available.