A Google Project Member on the Android Open Source Project forum, replying to 'Issue 60058: mm-qcamera-daemon cpu usage' post said, "We believe we have fixes for the current high CPU reports on N5 (Nexus 5) due to mm-qcamera-daemon, and they will be included in the next maintenance update."
However, the project member did not provide an estimate for when the maintenance update will be rolled out for the Nexus 5. The Google employee said, "Unfortunately, I can't provide an estimate for when the maintenance update will be ready, due to all the testing we need to do for this and other fixes. Until then, rebooting the phone is the only way to stop the high CPU usage/lack of camera function once it starts."
According to an IBTimes report, the Nexus 5's battery drain issue is because of a software process on the Android 4.4.2 KitKat build that allows applications to access the device camera. The mm-qcamera-daemon process continues to run in the background even after the app using the camera has been force closed, which leads to persistent high CPU usage and battery drains faster, notes the report.
One of the forum members complains, "This issue is happening to me as well. But when it does happen it uses about 50% of battery like most others. I go down about 1% every 2 minutes in just stand by when this process is running. I have had my Nexus 5 since November 17th. So only a couple weeks after it was released. I never had this issue when I was on 4.4. It only started on 4.4.2."
The Google project member further explains that the Nexus 5's battery issue has been reported frequently in the recent past, and claims might be related to a recent Skype update. According to the project member, the new update to Skype allows the app to access the device's camera continuously in the background and might trigger a bug.
The project member notes, "Uninstalling Skype may substantially reduce the likelihood of this bug appearing. Other camera-using applications may trigger this bug as well, but that's been relatively rare."
It's worth pointing out that the report claims that the 'mm-qcamera-daemon' issue is affecting all Android 4.4 KitKat-based and Qualcomm-powered devices.
The project member acknowledged, "I'd also like to note that instances of high CPU use of mm-qcamera-daemon on other devices besides the N5 (Nexus 5) need to be reported to their manufacturers - while those devices also use a Qualcomm chip for their camera processing (and thus have a mm-qcamera-daemon process), each has differences in their software and issues with them do not necessarily mean the N5 has the same problem, and vice versa."
Google is known for fixing issues with its Nexus devices as quickly as possible; back in in December when some Nexus 5 users sent their devices back to the company with certain issues that included noisy buttons, a protruding SIM tray and "cutting-edge" display frame. Google, later rolled out new batch of Nexus 5 which were said to come with more flushed buttons to avoid noise and fixed protruding SIM tray.