• Posts
  • RSS
  • ◂◂RSS
  • Contact

  • Android Sound Synthesis and Latency

    January 27th, 2012
    music, phone, tech  [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:

    Randal O’Toole Gets High-Speed Rail Wrong

    Now that there’s decent chance of US investment in rail, Randal O’Toole is resurrecting his takes from the early Obama era, warning that high-speed rail is a multi-trillion dollar money sink. It’s not a good analysis, and in particular it gets the reality…

    via Pedestrian Observations May 12, 2021

    Collections: Teaching Paradox, Europa Universalis IV, Part II: Red Queens

    This is the second part in a series (I) that examines the historical assumptions behind Paradox Interactive’s grand strategy computer game set in the early modern period, Europa Universalis IV (EU4). Last time, we took a look at how EU4 was a game fundame…

    via A Collection of Unmitigated Pedantry May 7, 2021

    Books and websites on babies

    Several people I know are expecting a first baby soon, and I wrote up notes for one of them. Might as well share here too: Medical:Scott Alexander’s Biodeterminist’s Guide to Parenting is an interesting read, and some parts are actionable.  If you live in…

    via The whole sky April 14, 2021

    more     (via openring)


  • Posts
  • RSS
  • ◂◂RSS
  • Contact