We all love listening to music on our phones. In fact, listening to music, audiobooks, or podcasts regularly on our smartphones is probably one of the few things we all really share in terms of our usage patterns. The problem with listening to audio for extended periods, though, is that it can really put the hammer down on your battery life. Now, there's more than one reason for this - streaming high-quality audio over the web probably consumes more battery than the actual act of listening, but the power consumption of the processor while decoding that audio isn't negligible.
To address the latter issue, Google has introduced audio tunneling to DSP in Android 4.4. The premise is simple - instead of using the application processor to decode audio or respond to audio output requests, this responsibility is offloaded to the onboard DSP (digital signal processor). The DSP is much more efficient at such tasks than the CPU, and as such, Google estimates that the amount of power used playing back audio on your phone could decrease in excess of 50%! That's pretty impressive. In a local playback test (that is, non-streamed audio), the Nexus 5 extended its playback time from 30 hours without DSP tunneling to 60 hours with the new feature enabled.
The downside is that not all chipsets will support the feature, and that the Nexus 5 is currently the only device to take advantage of it. Google claims to be "work[ing] with our chipset partners" to get more devices on board, but we'll have to wait and see what that means for existing hardware. Given that the Nexus 5 uses a Snapdragon 800 chipset, it would seem plausible that DSP tunneling could come to some other S800-based products via an Android 4.4 OTA update, but it's still far from a given.
Be sure to checkout our other KitKat feature spotlights, more of which will be going up throughout the day.