We all use our smartphones differently.
Some people rely on them for web browsing and apps, some for texting,
and many of us still resort to making calls, you know, when we have to.
Even within those categories, several patterns emerge and certain habits
and practices have been developed. Many of us have long since abandoned
using wired headsets for calling, but a lot of people still prefer them
to keeping Bluetooth headsets charged or holding a 5-inch phone against
an ear. Unfortunately, these simple wired accessories can also be
plagued by bugs like anything else, and both the Nexus 4 and 5 seem to
suffer from a pretty big one. It turns out that the recording level for
these inline microphones can be painfully low, making conversations
difficult, if not impossible.
Symptoms
There aren’t a lot of variables here, just one clear and specific
problem: the input gain on in-line microphones is incredibly low on the
Nexus 5 and Nexus 4. People on the other end of a conversation describe
the person talking as sounding like they are on the other side of the
room. Sometimes, the problem can be so bad that the speaker can't even
be heard.
It’s worth noting, this bug isn’t limited to making calls. Any
application that takes sound from the inline mic is handicapped by this
issue. Obviously, this can impede things like Google Now, voice
dictation, and many other common activities.
Sample recordings taken with and without headsets. Credit: MattPneumatic
Causes
At its core, the issue appears to originate in the
Automatic Gain Control
(AGC), a piece of software responsible for adjusting the input gain
based on the quality of a signal. For example, if the line quality were
very low and the incoming signal too quiet, the gain would be boosted to
make it audible. It seems that the AGC is becoming confused and
reversing the effect. A few users
discovered the likely culprit after using apps with the ability to disable the AGC while making recordings.
Another contributing factor - or possibly the whole problem - may
trace to something as simple as inconsistent wiring of the headset
jacks. Believe it or not, there are two slightly different standards for
those tiny little plugs: OMTP and CTIA. An original standard was
created years ago by the
Open Mobile Terminal Platform (OMTP)
in an effort to unify accessories for use across handsets from all
OEMs. This is the standard originally created and used by companies like
LG, Samsung, Blackberry, and virtually everybody else. The newer, but
nearly identical wiring arrangement appears to have been created by
Apple and supported as a standard by
CTIA. Yes, this is one time we should all get angry, because this is really stupid...

Many headset manufacturers initially began producing
iPhone-compatible variants alongside the originals. However, as those
headsets became dominant, many of the OEMs have switched their hardware
to CTIA to conform to market demands. The Nexus 4 and Nexus 5, still
uses the OMTP pin out pattern, as do all phones manufactured by LG and a
few other OEMs. In most cases, this doesn’t matter because software
drivers can be written to detect and automatically adjust to the type of
jack, but it’s possible this functionality was forgotten or
malfunctioning in the code for the two Nexus handsets. If handled
improperly, this difference could explain the low input gain. Take note,
this is speculation and may have nothing to do with the problem.
Workarounds
The options for workarounds are a bit limited, but there are a few.
The best, but most expensive option is to replace your current wired
headset with one known to be working, or move over to Bluetooth headsets
which don’t suffer from this issue. The wired headsets that have been
reported by others to work are the Yurbuds Inspire Talk Sport and many
of the V-Moda models. If you happen to live in a country where LG also
distributed the mic-equipped earbuds, they also seem to work quite well.
For a cheaper alternative, some people have tried OMTP-to-CTIA
adapters. Oddly, the results have been mixed. In some cases, it seems to
completely resolve the issue, but others report it can make things
worse. These adapters are very cheap, but given the hit-and-miss nature,
they might not be worth the trouble.
If your existing headset is equipped with a button for hanging up on a
call or otherwise controlling audio playback, there is a creative hack
that might work for some people. By holding down the button when first
plugging in the jack, a connection is shorted and the phone is tricked
into believing the headset lacks a microphone. When making a call, this
results in pushing audio through the earbuds, but enables the
speakerphone on the handset. This isn't suitable for everybody, but it
might be a good workaround until a proper fix comes.
Wrap-up
In a dash of perfect timing, an
announcement
of a fix for the Nexus 5 was posted in the Google Product Forums at
exactly the same time I was writing this article. Unfortunately, the
statement isn’t clear if there will also be a fix for the Nexus 4, but
given the obvious similarity, there’s no good reason to overlook it.
Even if this is a driver issue, as it likely is, the same fix should
work across both handsets.
A release date for the patch hasn’t been divulged, but it’s likely to
come with the next OTA. Since updates typically flow pretty steadily in
the first couple of months after a major release, this issue should be
resolved fairly soon.
Sources: Google Product Forum 1, 2, 3, AOSP