Google today provided an update on the state of audio latency to encourage developers that “have been holding back on developing an Android app” in this category.
This effort is the result of “Google working directly with OEMs to reduce audio latency” four years ago. It started in 2017 with Android 8.0 introducing the AAudio API and 8.1 later featuring “enhancements to reduce latency when used in conjunction with a HAL and driver that support MMAP.”
Google says these actions, along with the open source Oboe wrapper that now has over 4 billion installs, “led to significant improvements in the device ecosystem.” One milestone was the Pixel 3a in 2019 becoming the first Android phone with 10ms latency.
The average latency of the most popular Android phones has dropped to under 40ms, which is well within the range required for real-time applications.
This current 39ms round-trip audio latency time is a notable drop from 109ms in January of 2017. More broadly, Google reports greater consistency in the last four years. In 2017, there was a 222ms difference between the highest and lowest values among the most popular phones.
Today, the “range has reduced by a factor of 8 to just 28ms” for a “far more consistent audio experience.”
This is more impressive when you consider that there are now multiple OEMs on the most-popular list, compared to only a single manufacturer in 2017. In addition, many of the devices on the list are not high-end flagship models.
Another metric to look at, especially for real-time audio applications, is tap-to-tone latency, or the “time taken from tapping on the screen to hearing a sound.”
To estimate tap-to-tone latency given round-trip latency, you can subtract the audio input latency (typically 5ms), and add the touch latency (typically 20ms). In other words, add 15ms to the round-trip latency. Given the numbers above, this means the average tap-to-tone latency of the most popular Android phones is also well under that required for most real-time audio applications.
Moving forward, Google’s long-term goal is to reach 10ms round-trip latency, with 20ms currently required for professional Android audio apps.
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