::  Posts  ::  RSS  ::  ◂◂RSS  ::  Contact

Android Sound Synthesis and Latency

January 27th, 2012
music, tech, phone  [html]
Playing with people's iPhones I really enjoy music apps. Even though there's no real tactile feedback they're still really fun to play. When I got a computer with a responsive and accurate multitouch trackpad I wrote one for it. Now that I have a smartphone I wanted to write something similar: map regions of the screen into notes.

I started with libpd for Android, which is a port of libpd to Android, which is a library version of the audio engine from Pure Data. Learning enough Android programming to get this loading on my phone was a little annoying, as was figuring out how to modify the CircleOfFifths example app to play single notes, but I got something working. Unfortunately, the latency is terrible. I put down my finger, and there is a significant delay before sound comes out of the device. This isn't just my experience; round trip generate-speaker-mic-record latency with libpd on Android tends to be around half a second. Measuring mine with their tester I got 558ms.

While this is way high, I thought at first the problem might be with libpd and that by using the lowest level API directly I might get good performance. Unfortunately, it sounds like this is not the case: the best you can do on the best devices is about 50ms, which is still too slow. If you read the Android Audio mailing list, this is nearly all they talk about back to the third message on the list. There's a bug registered, and it's in the top 10.

It looks like the main problem is that most devices are not designed for it. To get 5ms latency at 44KHz you need to be able to get the buffer down to 256 [1] samples and keep it from emptying. Most Android devices have a minimum buffer size over ten times that. I don't think Google's going to be fixing this soon. This is sad. I want to make music live with my phone.


[1] Really 220 samples, but we like powers of two.

Comment via: google plus, facebook, r/androiddev

Recent posts on blogs I like:

I’m Giving a Talk About Construction Costs Tomorrow

By popular demand, I’m giving the talk I gave 2 weeks ago at NYU, again. The database will be revised slightly to include more examples (like Ukraine, which I added between when I gave the talk and when I blogged about it), and I may switch around a few t…

via Pedestrian Observations December 2, 2019

Your room can be as bright as the outdoors

The effect was huge: I became dramatically more productive between 3:30pm and whenever I turned off the light. I estimate the lamp bought me between half an hour and two hours a day, depending on how overcast it was.

via benkuhn.net November 26, 2019

git-subtrac: all your git submodules in one place

Long ago, I wrote git-subtree to work around some of my annoyances with git submodules. I've learned a lot since then, and the development ecosystem has improved a lot (shell scripts are no longer the best way to manipulate git repos? Whoa!). Thus, I …

via apenwarr November 24, 2019

more     (via openring)

More Posts:


  ::  Posts  ::  RSS  ::  ◂◂RSS  ::  Contact