My application is measuring volume of captured audio as a function of samples absolute amplitude.
I've noticed and unexpected behavior in android.media.AudioRecord of Android SDK. Let's assume following flow:
Application is launched
Audio volume is being measured
Phone call is answered/dialed
Audio volume is being measured
The noise around the microphone is produced by TV with constant volume setting. Values measured for point 2 are in range [55-65] and values measured for point 4 are in range [15-25] (please see the audio visualization for 2. and 4. below).
I understand that there must be some volume adjustment going on when phone call occurs. Is it possible to monitor those adjustments or to get rid of them?
I've tried AutomaticGainControl but it is not supported on my Nexus 5 and I do not want to use it since the target devices might not support it as well.
Update
This volume adjustment is happening not only after phone call. I've just noticed the same behavior when phone was just lying on the table measuring volume.
In regard to resources that your app is sharing with other apps (the microphone in this matter) - you should always treat them carefully and assume there configuration may change during a phone call or other usage like switching to another app that's using the microphone.
Instead of trying to monitor for changes in gain , which may require root or other elevated privileges - I would take another approach and do the following:
Save the mic sensitivity level to a configuration file (shared_prefs) in your recording activity when the user is recording . do the same if the user changes it of course during usage of your app.
In the onResume proc of your recording activity - load the mic sensitivity level value and set it before continuing to record (How to adjust microphone sensitivity while recording audio in android - Solved)
If there is a phone call that throws your app to the background and takes control of the mic, once it's finished - your app will return to the foreground and retain the mic sensitivity level for further recording.
Hope this helps.
Related
In my app I have an additional library for SIP calling, which on some phones (Huawei 5.1) locks volume to around 50% (or even less) for some reason and it keeps it like that for the whole phone volume meanwhile service is running.
I tried setting:
am.SetStreamVolume(Android.Media.Stream.Music,am.GetStreamMaxVolume(Android.Media.Stream.Music), 0);
And playing beeping noise with MediaPlayer/Soundpool.
I also tried setting Microfone to
Mode.Ringtone / Mode.Normal,...
but the volume is still low when this library/service is running.
Is there any other setting option possible that could override some setting in the library, because if I look current volumes, it's all on MAX (Media/Notification/Ringtone/...)?
In this library, you have to initialize sampleRate / buff size, which I do with getting default values from Android
String rate = audioManager.getProperty(AudioManager.PROPERTY_OUTPUT_SAMPLE_RATE);
String size = audioManager.getProperty(AudioManager.PROPERTY_OUTPUT_FRAMES_PER_BUFFER);
Some companies add a volume limit to protect user. I met similar issue before on samsung note 4. I am not sure whether APP has the permission to break this limit(mostly not allow).
In order to find the relative setting, please try this: Play music by the default music player, and press volume+. Keep volume up and then your phone may toast a dialog to tip you. And you can change this setting.
Hope it works :)
I would like to measure power transmitted to speaker/headset by playing music on the phone using android code . I do not want sound felt at microphone to be measured because it may contain noise as well.
There is nothing in the Android SDK to measure this, sorry.
Is there any API (Provided by Android ) to measure the frequency of sound. I searched about this but didn't get any appropriate API to do that.
for example: I saw a Screen Lock in some device which opens whenever user blow a wind in a particular direction,which gives me an idea about this.
I am developing an android application which records audio in PCM using the AudioRecord API. I want to adjust the mic sensitivity to low, medium and high as the user chooses it in the settings.
Is it possible to adjust the mic sensitivity? Your answers will be highly appreciated :)
Not really. It's usually possible to get at least two different "sensitivities" (acoustic tunings used by the platform) implicitly by using different AudioSources.There should at least be one tuning for handset recording and one for far-field recording. On some devices you might also have different far-field tunings, e.g. one for recording audio a few decimeters away and one for recording audio a few meters away.
The problem is that you can't really know which AudioSource corresponds to which tuning, as there's no standard for it. CAMCORDER typically means far-field, and VOICE_RECOGNITION often means handset mode, but there's no guarantee for it. You should also keep in mind that vendors typically apply automatic gain control, noise reduction, etc that you as a user / app developer can't disable, in order to meet acoustic requirements for their products.
Your best bet would probably be to use a single AudioSource and then do attenuation of the signal in your app to simulate a lower mic sensitivity. You could do amplification as well, but that would be akin to using digital zoom in the camera app (it works, but doesn't look all that good because you're just scaling the existing data).
I'm trying to build a gadget that detects pistol shots using Android. It's a part of a training aid for pistol shooters that tells how the shots are distributed in time and I use a HTC Tattoo for testing.
I use the MediaRecorder and its getMaxAmplitude method to get the highest amplitude during the last 1/100 s but it does not work as expected; speech gives me values from getMaxAmplitude in the range from 0 to about 25000 while the pistol shots (or shouting!) only reaches about 15000. With a sampling frequency of 8kHz there should be some samples with considerably high level.
Anyone who knows how these things work? Are there filters that are applied before registering the max amplitude. If so, is it hardware or software?
Thanks,
/George
It seems there's an AGC (Automatic Gain Control) filter in place. You should also be able to identify the shot by its frequency characteristics. I would expect it to show up across most of the audible spectrum, but get a spectrum analyzer (there are a few on the app market, like SpectralView) and try identifying the event by its frequency "signature" and amplitude. If you clap your hands what do you get for max amplitude? You could also try covering the phone with something to muffle the sound like a few layers of cloth
It seems like AGC is in the media recorder. When I use AudioRecord I can detect shots using the amplitude even though it sometimes reacts on sounds other than shots. This is not a problem since the shooter usually doesn't make any other noise while shooting.
But I will do some FFT too to get it perfect :-)
Sounds like you figured out your agc problem. One further suggestion: I'm not sure the FFT is the right tool for the job. You might have better detection and lower CPU use with a sliding power estimator.
e.g.
signal => square => moving average => peak detection
All of the above can be implemented very efficiently using fixed point math, which fits well with mobile android platforms.
You can find more info by searching for "Parseval's Theorem" and "CIC filter" (cascaded integrator comb)
Sorry for the late response; I didn't see this question until I started searching for a different problem...
I have started an application to do what I think you're attempting. It's an audio-based lap timer (button to start/stop recording, and loud audio noises for lap setting). It' not finished, but might provide you with a decent base to get started.
Right now, it allows you to monitor the signal volume coming from the mic, and set the ambient noise amount. It's also using the new BSD license, so feel free to check out the code here: http://code.google.com/p/audio-timer/. It's set up to use the 1.5 API to include as many devices as possible.
It's not finished, in that it has two main issues:
The audio capture doesn't currently work for emulated devices because of the unsupported frequency requested
The timer functionality doesn't work yet - was focusing on getting the audio capture first.
I'm looking into the frequency support, but Android doesn't seem to have a way to find out which frequencies are supported without trial and error per-device.
I also have on my local dev machine some extra code to create a layout for the listview items to display "lap" information. Got sidetracked by the frequency problem though. But since the display and audio capture are pretty much done, using the system time to fill in the display values for timing information should be relatively straightforward, and then it shouldn't be too difficult to add the ability to export the data table to a CSV on the SD card.
Let me know if you want to join this project, or if you have any questions.