Why does my phone connect to car but not music?

When Your Phone Won’t Play Tunes In The Car

We’ve all been there before – you get into your car, connect your phone via Bluetooth to make calls, but when you try to play music nothing happens. Or even worse, the music plays for a minute and then cuts out. How annoying!

While it’s convenient that our phones can interact with our car’s systems wirelessly, this technology doesn’t always work perfectly. You might find your phone will connect for basic functions like calls or podcasts, but more data-heavy uses like streaming music from Spotify or Apple Music just won’t work.

There are several key reasons why you may experience issues with music playback over Bluetooth in your car, even if basic connectivity is working. In this article we’ll explore the main culprits like Bluetooth profiles, bandwidth limitations, antenna issues, codecs, software problems, and Digital Rights Management. We’ll also provide some tips to troubleshoot or work around the problem if possible.

Bluetooth Profiles

Bluetooth uses profiles to define which features and capabilities a device supports. Some key profiles for audio include:

A2DP (Advanced Audio Distribution Profile) – handles high quality stereo audio content like music streaming. Supported by devices like wireless headphones and speakers.
HFP (Hands-Free Profile) – handles phone calls and voice commands. Supported by hands-free car systems and wireless headsets.

HSP (Headset Profile) – similar to HFP but supports only the most basic call functions. Used by basic headsets and mono Bluetooth speakers. [1]

Cars and headsets typically only support HFP/HSP since their main function is phone calls and voice, not high fidelity music. On the other hand, wireless headphones and speakers support A2DP in addition to HFP/HSP in order to stream stereo audio.

This profile difference is why your phone may connect to your car for calls but not for music streaming. The car only supports HFP while your phone requires A2DP for playing songs.

Bluetooth Versions

Bluetooth technology has gone through several iterations, with each new version introducing improvements in data transfer rates, connectivity range, power efficiency, and more. The most common Bluetooth versions in use today are:

Bluetooth 1.0 and 1.0B – Released in 1999, this version had a max data rate of 1 Mbps and range of 10 meters. It is now obsolete.
Bluetooth 2.0 + EDR – Introduced in 2004, it increased data rates up to 3 Mbps and introduced Enhanced Data Rate (EDR) for faster transmission.

Bluetooth 3.0 + HS – Released in 2009, it allowed high-speed data transfer up to 24 Mbps with the High Speed protocol.
Bluetooth 4.0 – Introduced in 2010, it added Bluetooth Low Energy protocol aimed at low power devices.
Bluetooth 4.1 – Released in 2013, mostly minor updates to 4.0.

Bluetooth 4.2 – 2014 update doubled 4.0 data rates and “Internet of Things” support.
Bluetooth 5 – Major 2016 update increased range up to 800 ft and speed up to 50 Mbps.

Many older cars only have Bluetooth 2.0 or even older versions, while most modern smartphones support 4.0 and above. The lower Bluetooth version in the car stereo system can negatively impact functions like music streaming. Newer versions allow higher quality audio codecs, faster data syncing, better range and connectivity, and simultaneous music and call functionality. Upgrading the car’s Bluetooth system would provide benefits unless the smartphone also has an older Bluetooth chipset.[1][2]

Bluetooth Bandwidth

One reason phones may have trouble streaming music over Bluetooth is limited bandwidth. Bluetooth has a set amount of data throughput capacity, measured in kbps (kilobits per second). This capacity varies across different Bluetooth versions and profiles.

For example, the Bluetooth Classic profile in Bluetooth 4.0 has a maximum throughput of 25 Mbps, while Bluetooth Low Energy in 4.0 has just over 300 kbps. The latest Bluetooth 5.0 can reach 2 Mbps. However, music streaming requires significant bandwidth – CD-quality audio is 1,411 kbps while high-res lossless audio can demand 2,300 kbps or more (Source).

To manage limited bandwidth, Bluetooth prioritizes certain data types over others. Phone calls require constant small packets of data, so they take top priority. Music streaming involves larger blocks of data and can be briefly interrupted without major impact. Therefore, Bluetooth may pause music playback or decrease audio quality to ensure call quality.

Digital Rights Management

Digital rights management (DRM) technology can sometimes interfere with streaming music from apps like Apple Music or Spotify when using Bluetooth connections [1]. DRM adds encryption to prevent unauthorized copying and sharing of digital media. This extra layer of encryption can tax the bandwidth of Bluetooth connections, potentially causing music playback issues like skipping tracks.

However, DRM does not affect Bluetooth functionality for phone calls because calls use very little bandwidth compared to streaming music. Phone calls rely on the Bluetooth Hands-Free Profile (HFP) which only requires 64kbps bandwidth for mono audio [2]. Music streaming uses the Advanced Audio Distribution Profile (A2DP) which requires much higher 320kbps bandwidth to transmit CD-quality stereo audio [2]. So DRM has minimal impact on basic call functions even as it degrades music streaming.

Antenna Differences

A key reason that a phone may connect to a car for calls but not music is due to differences in the Bluetooth antennas. Car Bluetooth systems tend to optimize their antennas for phone calls rather than music playback. On the other hand, music headphones focus their antenna design on providing high-fidelity stereo sound.

As explained in this guide on picking Bluetooth antennas for PCBs, “Picking the Right Bluetooth Antenna Types for Your PCB Design”, automotive Bluetooth needs to provide omnidirectional coverage for calls, while music headphones can focus more directionally in front of the listener. Custom antenna designs in each device are tuned for their specific purpose.

Additionally, as covered in this Quora post on “How do headphones work as an antenna”, music headphones are designed to pick up a wide range of radio frequencies for high-fidelity stereo reproduction. Car antennas may filter out certain frequencies to optimize voice call quality.

So in summary, the antennas in your car and headphones are optimized differently – one for calls, one for music. This can lead to your phone connecting to the car but not playing music properly.

Audio Codecs

Different Bluetooth audio codecs have different purposes and capabilities. The most basic codec is CVSD (Continuous Variable Slope Delta modulation), which is designed mainly for phone calls and provides poor music quality. CVSD can only handle a 64kbps bitrate and 8kHz sample rate, resulting in low bandwidth and fidelity for music playback.

For better music quality over Bluetooth, more advanced codecs like aptX, AAC, and LDAC are needed. aptX was developed by Qualcomm and can handle bitrates up to 352kbps with a 48kHz sample rate. This allows CD-like or near CD-like audio quality wirelessly. Popular on Android phones, aptX provides a significant boost over basic SBC Bluetooth audio.

AAC (Advanced Audio Coding) is Apple’s preferred codec and also offers improved music playback compared to SBC, with a 250kbps bitrate cap. Sony’s LDAC goes even further with a maximum 990kbps bitrate and 96kHz sample rate for hi-res wireless audio.

Software Issues

Buggy phone software can often be the culprit behind Bluetooth connectivity problems. Issues with the phone’s operating system, firmware, device drivers, or Bluetooth software stack may prevent stable Bluetooth connections (1). For example, some Samsung and Android phone users have reported dropped Bluetooth connections after recent software updates. Bugs introduced in new firmware versions can disrupt the ability for the phone to communicate properly over Bluetooth.

The good news is that software issues can usually be resolved by restarting the phone or installing software updates. For persistent problems, some troubleshooting steps like resetting app preferences, clearing Bluetooth caches and data, uninstalling updates, or even factory resetting the device may be required. But in most cases, a simple restart is the easiest first step for any software-related Bluetooth problems (2).

Overall, being aware that phone software bugs are a common source of Bluetooth connectivity issues can help guide troubleshooting. Simple steps like restarting, repairing or updating software, and resetting Bluetooth connections often resolve the problems.

Workarounds

If you are unable to resolve the Bluetooth connectivity issues between your phone and car stereo, there are some simple workarounds you can try:

Use an auxiliary cable – Connect your phone directly to the car stereo with a 3.5mm auxiliary cable. This provides a wired connection that can often be more reliable than Bluetooth, although you do lose some convenience by having a cable.¹

Get an FM transmitter – FM transmitters plug into your phone’s headphone jack and broadcast music over an FM frequency you can tune the car stereo to. While convenient, sound quality may suffer.²

Check antenna placement – Make sure your phone and car stereo have clear line-of-sight to maintain a strong Bluetooth signal. Avoid placing phones in bags or pockets.³

Update Bluetooth drivers – Make sure both devices have the latest firmware updates which can improve Bluetooth connectivity and performance.⁴

Reset network settings – On your phone, reset all network settings which will wipe any problematic paired devices or connections.⁵

Conclusion

In summary, there are a few key reasons why a phone may be able to connect to a car for calls but not for music playback via Bluetooth:

The most likely reason is that the car stereo only supports the Hands-Free (HFP) Bluetooth profile, which allows for calls but not the Advanced Audio Distribution Profile (A2DP) needed for music streaming. Cars with basic Bluetooth connectivity often only support HFP. Upgrading to a stereo that supports additional profiles like A2DP would enable music streaming.

Additionally, older Bluetooth versions like 2.1 have limited bandwidth that may prevent smooth music streaming while a phone call works fine. Newer versions like Bluetooth 5.0 have faster transfer rates to handle music and calls simultaneously.

Digital rights management (DRM) may also prevent music playback over Bluetooth to protect copyrights. Music apps must be designed to allow Bluetooth output, with proper content encryption.

Finally, music streaming requires a stronger, higher quality wireless signal than voice calls. Differences in antenna quality and placement in the phone versus the car stereo could disrupt music more easily than calls.

While frustrating, the technology limitations for consistent Bluetooth music playback in cars seem likely to improve in the future. As more stereo systems support advanced Bluetooth profiles, and Bluetooth versions and wireless hardware improve, music streaming from phones to cars should become a more seamless experience.