I have an audiocard with 4 input channels: mono, stereo, 3 , 4. Is there any sdk way to record 4th channel data?
Now I just can record only mono/stereo by AudioRecord.
According to the Android docs for AudioRecord, the only channel input configuration's available specified are AudioFormat.CHANNEL_IN_MONO or AudioFormat.CHANNEL_IN_STEREO.
However, it seems that much higher number of channel outputs are supported according to the AudioFormat docs (or are at least planned to be implemented if not already).
I think that this would be a challenge on its own to implement it yourself, but could be worthwhile doing (I didn't manage to see any obvious solutions for this or any open source code yet). However, an example on the app store does exist, so it is possible via the USB interface according to the USB Audio Recorder Pro App.
JUCE (a mostly audio based C++ library that can compile directly to Android .apk s) seems to be working on this as well but I haven't seen a solution to this yet (maybe in the very near future).
I think you would have to go directly into OpenSL (C++ with JNI) to get the raw audio being received and then pass this back into Java to do whatever you wanted to do with it. Probably worth investigating OpenSL recording through USB devices with something like this to get started.
I know this is a lot of links, but hopefully it will get you started if you did want to implement this functionality (comment a link if you ever did start it).
Otherwise I hope this helped anyways!
Have recorded 4th channel audio. I use tinyalsa through jni. github.com/tinyalsa/tinyalsa
In this way, data is recorded from /dev/snd/pcmC1D0c, but it's needed root access or a+rw rights on pcmC1D0c.
Related
This is a question in regards with capturing audio content on recent Android devices. I'm working at developing an Android app that must record unprocessed microphone audio. In the process of trying to figure out how this could be achieved, I came across the Android Compatibility Definition Documents (CDDs) which, since version 5.0 (API 21), state that “device implementations that declare android.hardware.microphone MUST allow capture of raw audio content [...]” (see any CDD from 5.0 and higher, under the Audio Recording section : https://source.android.com/compatibility/cdd).
On the other hand, I have found that there are several audio sources that can be selected under the MediaRecorder APIs and that in order “To record raw audio select UNPROCESSED. Some devices do not support unprocessed input. Call AudioManager.getProperty(AudioManager.PROPERTY_SUPPORT_AUDIO_SOURCE_UNPROCESSED) first to verify it's available” (source : https://developer.android.com/guide/topics/media/mediarecorder). The PROPERTY_SUPPORT_AUDIO_SOURCE_UNPROCESSED property was added in API 24.
Here’s where I would need help : I am confused about the fact that the CDDs indicate that capturing raw data MUST be allowed while the MediaRecorder does not always allow access to it. Perhaps is it that “raw” is not the same as “unprocessed”? Or perhaps this means that raw/unprocessed audio data is for system-level functions only, and not available to third-party developers.
Please note that, when I tested in order to verify if the unprocessed property was available on 3 different Android devices (including the Galaxy S8 with API 26), I never got a positive result.
This being said, can someone clarify why CDDs indicate that capture of raw audio content MUST be available when the unprocessed AudioMagager API property rarely seems to be available. Should I be accessing the raw/unprocessed audio content differently?
Thanks in advance!
The Android CDDs are for developers intending to port the Android platform to other devices/platforms and maintain cross compatibility for app developers. This means that the standard, lower level Android libraries will be able to access the functionality defined in the CDD, but you won't necessarily be able to.
I managed to find an example here from androidcookbook.info that goes through getting raw, uncompressed audio via AudioRecord.
If that doesn't suit your needs then I would 100% recommend checking out OpenSL ES if you haven't looked at/used it yet. It uses the NDK (in C++) to provide a native interface so latency is much lower and you have access to more functionality for audio processing. Here' google's audio-echo project on GitHub that shows recording and playback in real-time using the native processing route with OpenSL ES.
I am sure you have access to the uncompressed audio by using it. You can pass the information to and from Java / C++ as you wish.
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'm trying to decode a raw h264 stream on "older" Android versions.
I've tried MediaPlayer class and does not seem to support the stream format.
I can see the stream on other Cam Viewer apps from the market, so I figure there must be a way to do it, probably using the NDK.
I've read about OpenMAX and Stagefright, but couldn't find a working example about streaming.
Could someone please point me in the right direction?
Also, I'm reading in several places about "frameworks/av/include/media/stagefright/MediaSource.h" and other sources, but they don't seem to be either in the regular SDK or the NDK.
Where is this source located? is there another sdk?
Thanks in advance.
Update: I'm receiving a rtsp connection.
If you wish to perform only a simple experiment to verify certain functionality, you can consider employing the command line stagefright utility. Please do consider this condition where your streaming input may not be supported.
If you wish to build a more comprehensive player pipeline, you can consider the handling for rtsp as in here or http as in here. Please note that NuCachedSource2 implementation is essential for streaming input as this provides a page cache implementation which acts as a jitter for the streaming data.
Please do note one critical point: Command line stagefright utility doesn't render to the screen. Hence, if you wish to render, you will to implement the complete playback pipeline with rendering.
On a related note, if your input is streaming input, the standard player implementation does have support for streaming inputs as can be observed here. Did you face any issues with the same?
As fadden has already pointed out, your work is made far more simpler with the introduction of MediaCodec in Android 4.x.
You should use third-party libs like android-h264-decoder which uses JNI for increasing the performance! Also look at this lib Intel
Update: Media codec wasn't exposed until API 16 (Android 4.1), so that won't work for a 2.3.3 device.
Stagefright and OpenMAX IL were (and still are) internal components of Android. You can find the code (including MediaSource.h) at https://android.googlesource.com/platform/frameworks/av/+/master Note that the media framework has moved to a separate "tree" frameworks/av only recently. Before it was part of 'frameworks/base', e.g. https://android.googlesource.com/platform/frameworks/base/+/gingerbread/media/
I'm currently working on an Application which is observing the microphone's input, but at the same time has to be able to play a specific MP3 song via Loudspeakers. The problem I'm currently facing is that as soon as I play the MP3 back, the microphone of course recognizes this and gives me a lot more data back, due to the increased volume.
I need to cancel the echo of the MP3, I've tried Android's own AcousticEchoCanceller, but it did not work as it's not even available on neither my Nexus 7 nor my Nexus 4. Now I came to speex, but I'm not really familiar with the NDK, and I don't know how to embed this into my existing code.
So I found this: https://github.com/mutantbob/ndk-speex NDK-Speex with Java wrapper classes, but unfortunately the classes seem to only be for Encoding and Decoding sound in the Speex-format, which seems to not cancel any echos. I've read about extending the Java wrapper to add echo cancellation, but I can't find the right start point, could anyone point me in the right direction? Or should I take a different route to my goal?
There are many good examples on how to use the NDK. Once you are familiar with the NDK, you can integrate any echo cancellation software that provides the best audio quality to your application.
I am trying to get a better understanding of android audio framework (froyo onwards in particular).
I've almost got the distinction into streams. The AudioFlinger maps each stream into a "strategy" and then routes a strategy to the proper "device" (BT, Headset, Speaker..)
However I still struggle to understand:
1) How multiple apps play onto the same stream? can they just 'play' or do they have to handle the focus (request, abandon and listen for changes)?
2) When multiple streams are playing...what is the priority of one stream respect to another? surely the in-call stream has top priority but are there any "rules" to understand how things really work.
If anyone with more confidence on this matter has got any doc/resource to study.. it would be great.
Thanks!
Marco
The answer to this question
Concurrent Sound on Android Device
may help you.
Also, here
http://www.droidnova.com/creating-sound-effects-in-android-part-1,570.html
is written how to initialize the SoundManager with the number of concurrent streams you want to play.
If you need to understand the default behavoiur you can see the Cplusplus code at
/hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp
However each vendor can make changes and ship a different flavour