The android audio manager has a large number of different audio streams available, including DTMF, SYSTEM, RING etc.
Not that I'm saying its a good idea, but is there any significant disadvantage to playing audio on a stream other than MUSIC? The standard appears to be to play on the MUSIC stream, but if, for example, I want to use the ringer volume, is there any disadvantage to just playing on the RING stream instead?
There are a number of cases where playing on streams other than music offer some advantages in addition to the case I provided above, but I don't want to risk breaking more important functionality if I can help it.
I'd be curious to hear whether anyone has any experience playing on and/or manipulating other streams, and what side affects, if any, they've encountered (or incurred...)
Why do you need it? I think media stream is enough for any of your purposes.
Look, for example you use ring stream. And for example your program controls it volume. He sets "no volume" => it means that he goes into "vibrate mode" and he cant hear incoming rings because of your application
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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.
I am looking for a way to mix an audio into an already-playing mixed audio stream. For example, when a sound is being played half way through, I want to add in another sound to play together without interrupting the first sound to continue. I would also like to have an ability to withdraw a playing sound stream from the mixed playing stream. Going through Android's relevant document, I think that the only possible solution is to use native OpenSL ES via JNI to develop my own library where I can programmatically mix in/take out an audio stream from mixed audio streams. I would like to hear if anyone has a way to achieve it with less effort.
Thank you
Chris
Have you considered SoundPool?
http://developer.android.com/reference/android/media/SoundPool.html
I'm working on an android app that plays video (using video view). the video is meant to have both music (left and right) and narration, but I want to selectively be able to turn off the narration track in the MediaPlayer.
Is the way to do this correctly to encode by mp4 video file with 3 audio tracks (right left and narration) and then turn off the naration audio track with deselectTrack()?
Not clear to me from the documentation that MediaPlayer can handle more than 2 audio tracks.
If the audio tracks are limited to 2, would it make sense to run two media player simultaneously (synching them up with seekTo())when I want the narration track to play?
Thanks.
Sorry to burst your bubble, but...
1) You have a misunderstanding about what a "track" denotes. A track can have multiple channels (e.g., a stereo track has left and right channels). As I understand it, stereo is the extent of the Android AudioTrack implementation at present. I haven't yet checked if the OpenSL implementation is more extensive than the Java API.
2) Only 1 audio track can be selected at a time, so you wouldn't be able to have background and narration simultaneously in the way you were thinking.
3) Audio tracks can only be selected in the prepared state (i.e., not after playback has started). The documentation mentions this limitation is not ideal, so it will probably change in the future. If not for this problem, your goal could be accomplished with two audio tracks encoded in the stream, one with both background & narration, the other just background.
You will probably find it difficult to synchronize two MediaPlayers, but I haven't tried. Maybe this approach would be acceptable for your situation, although be forewarned the seekTo method isn't accurate. It depends on the encoding of the files.
Something I would try if I were you is to have two complete encoded videos, one with narration, the other without. Use two MediaPlayers and keep them both prepared. When you want to switch use seekTo to put the correct one at (or near) the desired location. That way you don't have to worry about synchronization. If the video is large, this method could use significantly more resources, though.
when a voice call is established, I want to play audio in an stream so that the one at the other end of the call can hear the audio, but as it is mentioned in documents it is not possible.
so I decided to play that audio through the speakers with maximum volume so that the microphone can hear it (in general this a really ugly workaround but as it is going to be done in a special situation in my app, no problem!!!).
now the problem is this that when the call is established the system reduces the volume of my audio. how to solve it ?
Is there any way to intercept or just-read the audio output in android device?
I need to read the whole audio output in PCM from inside myActivity, including media player application in background, voice from calls, MediaPlayer istances inside myACtivity, etc., everything that's going to played by speakers. Actually, if it was possible to read them separately, would be great as well.
I tried with AudioRecord, giving it as audioSource parameter every constant found in MediaRecorder.AudioSource with no luck, should I try different audioSources?
Is it a so low-level task that has to be handled within native layer?
The visualizer class is helpful. I use it to playback immediately played audio here.
This audio comes in very low quality, however, so it's only really good for visualization.