Sending audio to the speaker for playback on Android is easy, but is it possible to get a copy of the actual final digital signal? Let's say I have 2 apps running "MyApp" and "SomeOtherApp". My app sends audio to the speaker, but so does "SomeOtherApp". "SomeOtherApp" is not my app - it's a 3rd party app. Is it possible to get a copy of the mixed audio signal which is played to the speaker by the OS? That is, the audio signal which is a mixture of the speaker signal from my app and the speaker signal from "SomeOtherApp".
To summarize: I am looking for a way to hook into the low-level audio path (HAL audio stream out - after mixing!) so I can get a copy of the "final" speaker signal (in real-time). Optimally, I would also like to hook into the low-level microphone path, but that's less of a concern right now.
Looks like the short answer is no.
Longer one is kinda. And sorta. But not really, as far as I know. Option 1: it might be a problem with respects to privacy. (not really a good option) Option 2: nobody thought it was needed, so did not build it into the system. Option 3: the amount of trouble shooting when programmers use the wrong source is just not worth it.
edit - You can, of course, record the input.
Checkthis one google example
Usage :
App will capture audio from android devices and playback on the same
device; the playback on speaker will be captured immediately
*
Related
I'm messing around in my app with a custom model for speech commands - I have it working fine recording and processing input audio from an AudioRecord, and I give feedback to the user through text to speech.
One issue I have is that I'd like this to work even when audio is playing - either through my own text to speech or through something else playing in the background (music for instance). I realize this is going to be a non trivial problem, but if I could get access in some way to the audio output data (what the phone is playing) and match that up with my microphone input data, I think I can at least adjust my model for this + improve my results.
However, based on Android - Can I get the audio data for playback from the audio mixer? , it sounds like that is impossible.
Two questions:
1) Is there any way that I'm missing to get access to expected audio output/playback data through the android api, or any options the android api provides for dealing with this issue (the feedback loop between audio output and input)?
2) Outside of stopping all other playback or waiting for other playback to finish - is there any other approach to solve this problem? I would assume some calling apps have a way of dealing with this if the user is on speaker phone, I'm just missing how to do it myself
Thanks
Answers to 1 & 2: You want AcousticEchoCanceler.
A short lecture on why "deleting the speaker audio from the microphone input" input is a non-trivial task that takes substantial signal processing knowledge: It's more complicated than just time-shifting the speaker audio a little bit and subtracting it from the mic input. The fact is, the spectrum of the audio changes drastically even as it leaves the speaker (most tiny speakers have a very peaky response centered around 3-4KHz). The audio may bounce off multiple objects (walls, etc.) before it gets back to the mic (multipath interference). Different frequency components interfere at the microphone in different, impossible to predict ways, vastly changing the spectrum of the audio. And by the way -- if anything in the room moves, say, if you put your hand near the phone -- everything changes. That is why you don't want to try to write your own echo cancellation filter. Android has provided one for you, so you can write cool speakerphone apps and such.
This question might seem to be a repetition of the questions such as following:
How to play an audio file on a voice call in android
Background Audio for a Call in Progress - Possible?
The answers of these questions suggests that it is not possible to play a pre-recorded audio on a voice call in android. I want to know why it is not possible? What is the limitation (hardware/software)? Is it really a limitation or done purposely? Can we alter the source code of android to make it possible?
I think this is a limitation, imposed for security reasons and restricted at the OS level.
Let's analyze the security threat, first of all. If you were able to play custom audio files to the callee, a whole world of cons opens up: you could trick customer supports, you could pretend to be someone else, you could give unauthorized purchase confirmations, and so on. For this reason, neither Android nor iOS allows this functionality.
On Android, you won't be able to do so in a programmatic way, simply because the current APIs won't allow you to do so. It is stated in the official documentation as well, as pointed out here. If you dig into the source code, you can probably enable this feature by accessing the microphone output during a phone call, but that would require running your custom version of Android. A good starting point would be the AudioTrack source, available here.
EDIT: a good example of an audio mod involves enabling the Nexus 5 earpiece as a second loudspeaker (requires root). Can be found here.
After a thorough research, what I have come to know is that there are more than one limitations/hurdles to make it possible. These limitations/hurdles are at three different levels.
First limitation is at API level, because there is no high-level API to play sound files in the conversation audio during a call as mentioned in Android official documentation.
Second limitation is at Radio Interface Layer (RIL). RIL passes on complete control of the call to Radio Daemon (rild) of the Linux library which then further passes the control to the vendor RIL. That means we cannot manipulate voice call in android source code.
Even if we are able to remove these two limitations, we may still not be able to play audio file to an ongoing voice call. Because there is a third limitation. Every vendor has their own library of RIL that communicates with Radio Daemon (rild). This requires that vendor RIL to be open source which is not actually. Hardware vendors do not usually make their device drivers code available.
Detail discussion on this topic is present at this link.
This is software related due to the prioritization of audio routing in Android.
Take a look into the CallManager where you can dig into the method setAudioMode(). After the audio mode was set to MODE_IN_COMMUNICATION the following code is called
audioManager.requestAudioFocusForCall(AudioManager.STREAM_VOICE_CALL,
AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
From this point on the telephony service has the highest priority and won't let any other audio play in parallel.
Note: You can play back the audio data only to the standard output device. Currently, that is the mobile device speaker or a Bluetooth headset. You cannot play sound files in the conversation audio during a call.
See official link
http://developer.android.com/guide/topics/media/mediaplayer.html
By implementing the AudioManager.OnAudioFocusChangeListener you can get the state of the audiomanager. so by this if any music is playing in the background you can get the AudioManager states(playing and pausing is completely in developer hands) similarly......
Some of the native music players in android device where handling this, they restrict the music when call is in TelephonyManager.EXTRA_STATE_OFFHOOK.so this scenario is also completely in developer hand (whether to handle or not) if he is not handling both will play parallel y
I want to make an app that makes it possible to connect an iPod or mp3 player to my Android device and let the Android speakers function as external speakers.
The ideal situation would be to actually read from speaker output so I can connect a stereo mini jack cable.
Is it possible to read from the headset output with the Android SDK?
A second option would be to use a mono mini jack instead. I could maybe directly read from microphone and output as a music player. Although, having to use a mono mini jack would be a huge disadvantage, because most people don't own such a cable.
UPDATE
For my second option I found this link that would let me take a special adapter onto a stereo cable so the iPod output can go into the mic input. It's a TRRS adapter. This works, but still isn't the ideal solution to me. http://www.techlife.net/2012/12/add-an-audio-input-to-android.html
ANOTHER UPDATE
I did a test with only a mono cable, but it seems that the mic is not recognized, so I really need the TRRS adapter to make sure that the mic is on. I found some apps that can help me with measuring input volume. I think I can achieve my goal for myself with the adapter, but reading from headset output would be nicer and could actually result in building an app.
You need to understand some basic things...
Audio output lets you "take audio out of your device".
It's not audio input that would let you "insert audio signal into your device".
So the concept that you've presented cannot work, because this socket is not able to receive audio signal through normal stereo jack cable (and connector).
You could try to make it work with a device that supports the headphones/mic set (it's a different kind of 3.5 mm jack connector). It's so called TRRS (four-conductor). But to use it in your project you probably would need some cable/socket soldering and maybe even some sort of microporcessor to help processing the signals.
I am new to Android and Java and I need to know if this would be possible
I want to capture the sound input to the phone's microphone, perform some computations on this signal and output the modified signal to the earphones
Is processing the input to the microphone in real time like this possible?
THE ANDROID DEVELOPERS WEBSITE says that
Note: The Android Emulator does not have the ability to capture audio,
but actual devices are likely to provide these capabilities.
What does it mean by likely? Is it possible that some phones do not even allow reading from the microphone at all?
It is possible.
When you record the audio you can buffer it do some processing and then output it or save it or whatever....
There is an app for example that does the following thing when someone calls you:
It combines your voice with some sound you recorded and plays it in sync to the caller, making him think your are on a party, a bus etc....this is an example of processing the sound recorded.
Edit 1: Here is a similar topic that should guide you further how to implement this. Real-time audio processing in Android
I wrote an app that records audio. Everything works. However, I am going to be using this app to record class room notes. How can I boost the input of the microphone to better capture all the noise? I wouldn't mind using root if I must. But wasn't sure if there was an API to do this.
Thanks all for reading!
If you are asking how to make the microphone more sensitive, I'm not sure. That would involve either operating the microphone at a higher voltage and/or hacking the drivers, neither of which are doable programatically, AFAIK. However, you could try amplifying the output by multiplying the output by some value (say 1.1 for 10% volume boost). Of course, the more you "amplify" the output, the more you will saturate the speaker (aka distort the audio). There are some signal processing techniques you can try to remove background noise and to isolate the paticular audio of interest, however, these things are merely processing improvements, not hardware upgrades. You can always try plugging in an external microphone into the headphone jack and using that to record the audio.
I know this isn't the answer you were hoping for, but I hope it helps.