Background
Phone recording is not really supported on Android, yet some devices support it to some extend.
This made various call recording apps gather as much possible information about devices and what should be done to them, and decide upon this what to do.
Some even offer root solutions.
One such example is boldbeast Call Recorder app, which offers a lot of various configurations to change:
"record mode" . Shows 14 modes for non-rooted devices, and up to 34 for rooted. Also shows "Alsa mode" as an option for it, for rooted devices.
Has "Tune Audio Effect ("auto tune a groupd of parameters") .
Has "Tune Audio Route", with the possible values of "Disabled", "Group1", "Group2", "Group3"
For rooted devices:
"change audio controls" ("auto change audio controls")
"change audio driver" (change audio drive settings to enable record mode 21,22,23,24,31,32,33,34")
For rooted devices: "start input stream"
The problem
If I'm in need to create a call recording app, there is no other way than to find the various workarounds for various devices, but as it seems other apps use terms that don't appear in the API.
I can't find any of those of the app I've mentioned, for example.
What I've found
Other than tons of questions of how to record calls on Android, showing that it doesn't work on all devices, I could find some interesting things. Here are my tries and insights so far:
There are some Audio recording sources we can use while preparing the recording (docs here) , but sadly in each device it might be different. For some, VOICE_CALL works, and for some, others. But at least we can try...
On OnePlus 2 with Android 6.0.1, incoming calls can be recorded using VOICE_CALL, but I can't make outgoing calls be recorded there, unless I use MIC as audio source together with speaker turned on. Somehow, the app I've mentioned succeeds recording it without any issues. I'm sure I will see other issues with other Android devices, as I've tried to address this whole topic in the past. Update: I've found this sample project (also here), which for some reason sleeps for 2 seconds on the UI thread between prepare and start calls of the mediaRecorder. It works fine, and when I did something similar (wait using Handler.postDelayed for 1 second), it worked fine too. The comment that was written there is "Sometimes prepare takes some time to complete".
On Galaxy S7 with Android 8, I've failed to get sound of the other side for outgoing calls AND incoming calls (even with MIC and speaker), no matter what I did, yet the app I've mentioned worked fine.
To let you try my POC of call recording, I've published an open source github repository here, having a sample that will record a single call, and let you listen to the most recent one, if all works well.
This "ViktorDegtyarev - CallRecLib" SDK , which doesn't seem to work at all, and crashes on various Android versions
These 2 old sample projects : rvoix , esnyder-callrecorder , both fail to actually record. The second doesn't even seem to work on Android 6.0.1 device, which it's supposed to support.
aykuttasil - CallRecorder sample and axet - android-call-recorder sample - both, just like on my POC, don't have any tweaking except for AudioSource, and because of this they fails to record on some cases, such as OnePlus 2 output-audio of outgoing calls.
Most third party apps only offer the AudioSource tweaking, but some (like "boldbeast") do offer more. One example is "Automatic Call Recorder" which has "configuration" (10 values to choose from, first is "default") and "method" (5 vales to choose from, first is "default"). Those apps probably do not want others to understand what those configurations mean, so they put general names. Or, it's just too complicated for everyone (especially for users), so they generalize the names.
There is an API of "setMode" here, but it doesn't seem to change upon calling it. I was thinking of maybe change the "channel" of where the call is being used, this way, but it doesn't work. It stays on the value of "2" during call, which is MODE_IN_CALL.
There are customized parameters that are available for various devices (each OEM and its own parameters), which can be set here and maybe even via JNI (here and here) , but I don't get where to get this information from (meaning which pairs of key-value are available). I've searched in a lot of places, but couldn't find any website that talks about which possible parameters are available, and for which devices.
I was thinking of using AudioRecord instead of MediaRecorder class for recording, thinking that it's a bit low level, so it could give me more power and access to customized capabilities, but it seems to be very similar to MediaRecorder, and even use the same audio sources (example here).
Another try I had with low level API, was even further, of using JNI (OpenSL ES for Android). For this, I couldn't find much information (except here and here), and only found the 2 samples of Google here (called "audio echo" and "native audio"), which are not about recording sound, or at least I don't see them occur.
Android P might have official way to record calls (read here and here). Testing on my Android P DP3 device (Pixel 2), I could record both sides fine in both incoming and outgoing calls, using "DEFAULT" as audio source, so maybe the API will finally be official and work on all Android versions. I wrote about it here and here.
I was thinking that maybe the Visualizer class could be a workaround of recording, but according to some StackOverflow post (here), the quality it extremely low, so I decided that maybe I shouldn't try it. Plus I couldn't find a sample of how to record from it.
I've found some parameters that might be available on some devices, here (found from here), all start with "AUDIO_PARAMETER_", but testing on Galaxy S7, all returned empty string. I've also found this website, that gave me the idea of using audioManager.setParameters("noise_suppression=off") together with MIC audio source, but this didn't seem to do anything in the case of Galaxy S7.
The questions
As opposed to other similar questions about this topic, I'm not asking how to record calls. I already know it's a very problematic and complex problem. I already know I will have to address various configurations, and that I will probably use a server to store all of them and find there the best match for each one.
What I want to ask is more about the tweaking and workarounds :
Is there a list of configurations for the various devices, Android versions, and what to choose for each?
Besides Audio source, which other configuration is possible to be used?
Which parameters are possible for the various devices and Android versions ? Are there any websites of the OEMs describing them?
What are the various terms in the app I've mentioned? Where can I find information of how to change them?
Which tools are available for rooted devices?
Is it possible to know which device supports call recording and which not, by using the API ?
About the workaround of OnePlus 2, to wait a moment till we start recording, why is it needed? Is it needed on all Android versions? Is it a known issue? Would 1 second be enough?
How come on the Galaxy S7 I've failed to record the other side even when using MIC&speaker?
EDIT: I've found this of accessibility service being able to help with call recording:
https://developer.android.com/guide/topics/media/sharing-audio-input#voice_call_ordinary_app
Not sure how to use it though. It seems "ACR Phone Dialer" uses it. If anyone knows how it can be done, please let me know.
I spent many weeks working on a Voicecall Recording App so I faced all your issues/questions/problems.
Moreover: my project had a low-priority so I didn't spent much time every day on it, so I worked on this App for many months while Android was changing under the hood (minor an major releases).
I was developing always on the same Galaxy Note 5 using its stock ROM (without Root) but I discovered that on the same device the behaviour was changing from one Android release to another without any explanation.
For example from Nougat 7.0 to 7.1.2 I was unable to record a voicecall using the same code as before.
Google has enforced_or_changed restrictions about voicecall recording many times.
At the beginning it was sufficient to use use VOICE_CALL AudioSource. Then manufactures has started to interprete this Value as they wanted, and the result was that one implementation was working well but another was not.
Then Reflection was needed to run undocumented/hidden methods to start voicecall recording.
Then Google has added a Runtime check, so calling them directly was not more possible even using Reflection.
However this method lack of stability because it was not guarantee that a method was using the same name on all devices.
Then I started to reverse-engineer currently working Apps that were working on newer Android version and I discovered that them were using a complete different and more secure approach. This takes me many weeks because all these Apps uses JNI Libraries trying to hide this method between Assembler code.
When I succesfully create a Test App which was recording well I tried the SAME code in many different devices and ROMs/Versions and surprisely it was working well.
This means that all those different methods you can see in these App Settings (I'm 98% sure about it) are just "fake" or just refers to OLD methods not more used.
A small different metion should be done for Rooted devices:
these devices could change AudioRoutes so a different approach can be used in this case.
[1] There isn't any list or website listing all supported devices or best method to do a successfully voicecall record
[6] It's not possibile to know which device supports Voicecall Recording
just using an API call. You have to try and catch Excepions...
[8] Recording by MIC+speaker suffers of many issues: (1) the caller will hear all your ambient sound so the privacy-bug is a big issue (2) the echo is a big problem (3) the recording volume is very low as the quality of recordered voice
According to my tests, one way to improve this is to have an AccessibilityService being active (no need to write there anything at all) while choosing voice-recognition as the audio source. Also it's recommended to have the speaker turned on because this will record the audio from the microphone.
This seems to exist in some call-recording apps.
Weird thing is that Google has written this as a rule on the Play Store:
The Accessibility API is not designed and cannot be requested for
remote call audio recording.
https://support.google.com/googleplay/android-developer/answer/11899428
No idea what the "remote" means here.
Anyway, I've updated the Github repository to include these additions.
I want to be able to push a button in an app running on my Android phone and have a power switch on a real circuit literally attached to the phone be turned on/off. I'm having trouble thinking of a good way to do it. So far I've thought of:
1) Using an Arduino
The biggest problem with this is that the Arduino needs to be loaded with a sketch in order to work, and I can't use a PC to do the job. I've seen Arduino Commander but it's freemium and not open source, and I need to write my own custom app. It seems that I would have to find a way to load sketches and also write my own driver. This is not a pleasing course of action.
2) Playing an audio tone from the earphone jack
The idea is to play a tone that can then be converted into a small DC voltage. That DC voltage will then be used as the gate voltage to a MOSFET, which will act as the switch. The problem with this is that undesired audio can unexpectedly turn on the switch. For my application, even a small chance of this is unacceptable. Even filtering doesn't eliminate interference completely. Can I some how exclude all other sources of sound and only have an audio tone as output? If not over the headphone jack itself, over Bluetooth?
If anyone has any helpful thoughts, please share them.
You could try the second method with a specific audio to be played with some intervals which only triggers the switch instead of any audio being able to change the switch state, It does contain a little latency to be triggered but if its okay then it may work for you.
To clarify some miss information, the Arduino IDE is available at no charge for use on Windows, Mac OS, Linux, Raspberry pi and maybe others. With the IDE you can write, download your code to the Arduino and debut it.
I want to develop an android app.
One feature of the app is recognize 2 people's voice.
It will be kike this - when the app will open, 2 people will talk in front of it.
App will detect 2 persons speaking and will calculate how much % (let 2 persons are A and B) person A spoke and same for person B.
So, say, after 1 minute the app will tell A talks 80% and B talks 20%.
So, what I need is how to differentiate 2 people's voice.
I have tried SpeechRecognizer and android.speech.tts . But I can't make it working.
Is it possible in android to differentiate 2 people's voice?
Thanks in advance for helping.
SpeechRecognizer or TTS will not help you as they have designed to recognize speech. You have to use DSP technology, in order to recognize the speaker. Due to the complexity, i don't think you can achieve this within the device itself. You can save your audio (using something like AudioRecord in Android) and then send it to a server. in the server side you can run a speaker recognition program. ALIZE is a quite popular open source tool for this.
I want to make an android application that allow user change the voice during phone call. For example: You are a man, you can change the voice to a woman or robot when talking over phone. It is like a funny prank.
I work around android's API and google for some days but still have no idea. Some one told is impossible but I see some app on google play can do:
https://play.google.com/store/apps/details?id=com.gridmob.android.funnycall
So I think there are some ways to do that.
I think about recording and play back by using AudioTracker but I have 2more problem:
1. I cannot mute the voice from phone call, so the phone only play my sound after processing
2. record and process will make a long delay (slow-realtime)
Can any one share some solution for this?
The app you linked isn't changing voices on the phone: it uses SIP (or similar) to place a call through the authors' servers and the voice changing happens there. That's why you only get a small number of free minutes of use before you have to pay them.
Yes it uses a sip server to do this process. The reason you cannot actually create an app that does this on the phone is because of two things. The first thing being, sound processing for the phone is locked. You can't unlock this because its strictly engineered through hardware not software. A pc can do this because it uses a standard sound card in which software can modify its frequencies. The second thing is phone manufactures are required to design their phones in a standard format. There are laws that force these companies to make it impossible to do any voice morphing. It is against the law to impersonate someone you are not, over any telephone network.
Hard way
You get the input voice, you use voice recognition to detect the words, then you use speech-to-text with your desired voice as output.
Less hard way
Sound processing: Changing frequencies, amplitude etc.
I have a fairly popular application in Android market, which allows tens of thousands of its users to press a button and give it a voice command. Then I am able to do many different things, like give them current weather forecast, etc...
Anyhow, I came to a point where am getting asked almost every day by users of my app, that they don't want to be pressing a button all the time. They want my app to launch by a trigger word (some specific word command). In that way, app would wake up and ask them for a voice command, all hands free.
I understand that this would require a nonstop listening, it could be a battery eater, etc. But I want to give it a try. Anyhow, and this is why I am here.
I simply don't know how to go about it.
I know it's possible, these guys did it and not only that, they listen to a trigger word even when the phone is in the sleeping mode or behind a locked screen: http://www.youtube.com/watch?v=Dd2vo_9euOY
Any ideas on how this could be done? How did the guys above do it?
How? Any examples?
Thanks in advance.
NoiseAlert is an Application that launches when there is a loud ambient noise, it pays attention to the noise amplitude and also contains wakelocks.
You may use this as an reference. I think you have already implemented the Speeck recognition part.