CyanogenMod is a popular community which makes custom ROMs for a range of devices. The latest device to get a CM 10.1 custom ROM is HTC One. The nightly build of this ROM has been released. However, it has certain bugs! The biggest bug at the moment seems to be that the audio on outgoing calls can be “hit or miss”. The current workaround is to enable the ‘touch sounds’ and start a call using the dial pad, that way you will have audio on the outgoing call. This doesn’t affect incoming calls which are behaving normally.
If you want to still try out this ROM, then follow the instructions given below.