Android 4.4 brings support for low-power audio playback
Battery life – there's no smartphone owner who would mind having more of it. Even the best smartphones out there would have a hard time getting a hardcore user through more than two days of usage. And that sucks, doesn't it? Thankfully, Android 4.4 KitKat brings a tweak that will give battery life a slight boost. With the new version of the operating system, Google allows audio to be tunneled straight to the digital signal processor on the smartphone's chipset. This means that the DSP takes care of audio decoding and output effects, which reduces CPU usage and increases battery life as a result.
How much is battery life increased with this new technique? Well, real-life results will vary depending on how often you listen to music on your device, of course. The Google Nexus 5, for example, can last for 60 hours when playing music through a headset with its screen off. That's a 50% increase compared to a case when no DSP tunneling is applied.
Google notes that music playback isn't the only usage scenario that will benefit. Basically, any app that plays sound in one way or another, including the video player and video games, can take advantage of DSP tunneling. Best of all, no code modifications are needed as the system handles the process automatically.
Unfortunately, for the trick to work, support is required by the smartphone or tablet's hardware. Currently, The Android 4.4 powered Google Nexus 5 is compatible with DSP tunneling, but it isn't clear if any existing devices can take advantage of it once they are updated.
source: Android Developer Blog