Android update on audio latency
Android update on audio latency


Posted by Don Turner – Android Developer Relations Engineer

Header image of audio waves going through phone

This article looks at the recent changes in the Android ecosystem for audio developers, the audio latency of popular Android devices, and Android’s suitability for real-time audio apps.

What has changed?

Over the past four years we’ve taken a number of steps that have improved audio latency.

Timeline of the main events that affected the audio latency of Android devices. Before 2017: Google works directly with OEMs to reduce audio latency. Launch 2017: AAudio - New high-performance audio API is released. Mid-2018: Oboe - an open source C ++ wrapper for AAudio and OpenSL ES is released. Mid-2019: Pixel 3A is the first 10 ms Android phone. Mid 2020: OpenSL ES is out of date. Start 2021: Oboe has more than 4 billion installations

Latency reduction

These measures, together with a renewed focus by device manufacturers on audio latency, have resulted in significant improvements in the device ecosystem. The average latency of the most popular Android phones has dropped below 40 ms, which is well within the range required for real-time applications.

Bar graph showing the average audio latency of 20 most popular Android phones. In January 2017 it was 109 milliseconds. In January 2021 it was 39 milliseconds.

Device popularity source: appbrain.com

Greater consistency

If we look at the data, we can see that there was a significant difference between the highest and lowest value in 2017 (222 ms).

Bar graph showing the audio latency of the most popular Android phones in January 2017. There are 19 in total, all of which are Samsung Galaxy models. The average latency is 109 ms, the lowest value 36 ms, the highest 258 ms and the range 222 ms.

Device popularity source: appbrain.com

Compare that to the data for 2021. The range has been reduced by a factor of 8 to just 28 ms, which provides a far more consistent audio experience. This is more impressive considering that there are now multiple OEMs on the most popular list, compared to just a single manufacturer in 2017. Additionally, many of the devices on the list are not high-end flagship models.

Bar graph with the audio latency of the most popular Android phones in January 2021. A total of 20 with models from Samsung, Redmi, Oppo, Huawei and Vivo. The average latency is 39 ms, the lowest value 28 ms, the highest 56 ms and the range 28 ms.

Device popularity source: appbrain.com

Tap-to-tone latency

So far, I’ve been referring to round-trip audio latency. Round-trip latency has three components in the audio chain: audio in, audio processing, and audio out.

Many real-time audio apps generate audio from screen tap events instead of relying on audio input. These types of apps are sensitive to tap-to-tone latency – the time it takes from tapping the screen to hearing a sound. The latency caused by tapping the touchscreen is between 10 and 35 ms, with 20 ms being quite typical for modern Android devices.

To estimate the tap-to-tone latency with round-trip latency, you can subtract the audio input latency (typically 5 ms) and add the touch latency (typically 20 ms). In other words, increase the round-trip latency by 15 ms. Given the numbers above, it means that the average latency of the most popular Android phones is well below that required for most real-time audio applications.

Look to the future

Despite the significant reduction in audio latency across the Android ecosystem, our work is far from complete. Professional audio apps for Android require 20 ms of latency and 10 ms remains the long-term goal. And at this point in time, some less popular devices still have high audio latency. However, if you’ve been holding back on developing an Android app due to audio latency, it may be time to reconsider.

First read the oboe instructions or the video tutorials.

Data sources and tools

Oboe tester

WALT

appbrain.com

superpowered.com/latency

gsmarena.com

juce.com/maq

various internal data sources

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