Google today provided an update on the status of audio latency to encourage developers who “have held back from developing an Android app” in this category.
This effort is the result of “Google worked 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 with “improvements to reduce latency when used in conjunction with a HAL and driver supporting MMAP”.
Google says these actions, along with the open source Oboe wrapper which now has more than 4 billion installs, “have led to significant improvements in the device ecosystem.” A 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 less than 40ms, which is well within the range required for real-time applications.
This current 39ms round-trip audio latency is a noticeable drop from 109ms in January 2017. More generally, Google reports greater consistency over the past four years. In 2017, there was a difference of 222ms between the highest and lowest values among the most popular phones.
Today, “the range has been reduced by a factor of 8 to just 28ms” for a “much more consistent audio experience”.
This is more impressive considering that there are now several OEMs on the most popular list, compared to a single manufacturer in 2017. Additionally, many devices on the list are not top flagship models. range.
Another metric to consider, especially for real-time audio applications, is tap-to-tone latency, or “the time it takes between tapping the screen and hearing a sound.”
To estimate tap-to-tone latency based on round-trip latency, you can subtract audio input latency (typically 5ms) and add touch latency (typically 20ms). In other words, add 15ms to the round trip latency. Considering the numbers above, this means that the average tap-to-tone latency of the most popular Android phones is also much lower than required for most real-time audio apps.
Going forward, Google’s long-term goal is to achieve 10ms round-trip latency, with 20ms currently required for professional Android audio apps.
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