Bluetooth AVRCP in Android: What Is It and How Does It Work

The Audio/Video Remote Control Profile (AVRCP) is a Bluetooth profile that allows for the remote control of audio/video devices like headphones, speakers, TVs, etc. It enables devices to control media playback, volume, and other A/V functions on remote devices.

AVRCP was introduced in Bluetooth v1.3 in 2004 and has gone through several revisions since then. AVRCP 1.0 provided basic remote control functionalities like play, stop, pause, etc. AVRCP 1.3 added metadata transfer for track information. AVRCP 1.4 introduced browsing capabilities in 2008. The latest version AVRCP 1.6 was introduced in Bluetooth v4.0 in 2010 and added cover art transfer and advanced control features [1].

Adoption of AVRCP has steadily grown over the years as more Bluetooth audio devices have launched. It is now a standard profile included in most Bluetooth headphones, speakers, cars, TVs, etc. Support varies across device manufacturers and OS platforms, with some supporting only older versions of the profile.

How AVRCP Works

AVRCP utilizes a client/server architecture where the AVRCP controller acts as the client and the AVRCP target acts as the server. The AVRCP protocol defines several profiles that determine the capabilities and features supported.

Some key technical details of AVRCP include:

AVRCP uses the Audio/Video Control Transport Protocol (AVCTP) as the transport protocol over the L2CAP layer. AVCTP provides the basic transport capabilities for exchanging commands and responses (Bluetooth SIG, n.d.).

AVRCP defines a Media Control Profile that allows basic transport control commands like play, pause, stop, etc. This is mandatory for all AVRCP devices (Bluetooth SIG, 2019).
An advanced Remote Control Profile adds optional capabilities like metadata transfer, capability to display media info like track title, artist, album etc. This was introduced in AVRCP 1.3 (Bluetooth SIG, 2019).
AVRCP uses a browsing channel for transferring media metadata. The browsing channel is optional and was introduced in AVRCP 1.4 (Bluetooth SIG, 2019).

Overall, AVRCP aims to provide a standard interface and protocol for remote control of media playback between Bluetooth devices. The different AVRCP versions and profiles allow manufacturers to pick and choose capabilities based on the use case.

AVRCP Features

The main features provided by AVRCP are media playback control, metadata transfer, and cover art transfer.

Media playback control allows devices to remotely control media playback on another device. This includes commands like play, pause, stop, skip track, etc. AVRCP enables a Bluetooth remote to control playback on a phone or Bluetooth speaker for example.

Metadata transfer involves sending information like track title, artist name, album name, etc. from one device to another. This allows devices to display metadata about the currently playing music track.

Cover art transfer is used to send and display album artwork associated with the music being played. The cover art image can be displayed on devices like car stereos or wireless speakers to show which album is currently playing.¹

AVRCP in Android

Android has included support for AVRCP since version 2.3 Honeycomb in 2011. The AVRCP profile allows Android devices to remotely control media playback on other Bluetooth devices. Android supports AVRCP versions 1.0 through 1.6 as of Android 12.

Here are some of the key Bluetooth profiles that enable AVRCP functionality on Android devices:

A2DP (Advanced Audio Distribution Profile) – streams audio from one device to another over Bluetooth.
AVCTP (Audio/Video Control Transport Protocol) – allows devices to control AVRCP connections.

AVDTP (Audio/Video Distribution Transport Protocol) – manages streaming of audio over Bluetooth.
GAP (Generic Access Profile) – establishes connections between Bluetooth devices.

With support for these profiles, Android can remotely control media playback on headphones, speakers, cars, and other devices. Functions like play, pause, skip track, volume control are handled through the AVRCP Bluetooth profile.

Controlling Media Playback

One of the main uses of AVRCP on Android devices is to control media playback remotely. AVRCP allows you to perform basic playback control actions like play, pause, stop, skip track, fast forward, rewind, etc. This allows you to control music or videos playing on your Android device from another AVRCP capable device like a car stereo, Bluetooth headset, or Bluetooth speaker.

For example, if you are playing music on your Android smartphone using an app like Spotify, you can use buttons on your car’s dashboard to pause the music or skip to the next song without having to touch your phone. The car stereo essentially acts as a remote control for your Android device using AVRCP.

AVRCP uses specific commands called pass-through commands to facilitate playback control. Some common AVRCP pass-through commands used by Android devices include:

Play – Starts media playback
Pause – Pauses media playback
Stop – Stops media playback

Next Track – Skips to next track in playlist
Previous Track – Goes to previous track in playlist
Fast Forward – Fast forwards media

Rewind – Rewinds media

When you initiate one of these commands from a remote device, it passes the command via Bluetooth to the AVRCP service on your Android device, which then controls the media playback app accordingly. This allows seamless remote control of music, videos, podcasts and more.

Most Android apps with media playback capabilities like Spotify, YouTube, Netflix, etc. support AVRCP media playback control. However, the specific AVRCP commands supported may vary between apps. Make sure your Android device and the remote AVRCP device support the same AVRCP version for the best compatibility.

Displaying Metadata

One of the key features of AVRCP is its ability to display media metadata information like song title, artist, album, genre, etc. This allows devices like cars or Bluetooth headphones to display what song is currently playing on the connected Android device.

Android supports displaying AVRCP metadata through the MediaMetadata class in the Android framework. This contains all the relevant metadata keys for information like title, artist, album, etc. When a Bluetooth AVRCP connection is established, the MediaMetadata is passed to the connected device so it can be displayed.

The level of metadata supported depends on the AVRCP version. AVRCP 1.0 only supports track title. AVRCP 1.3 added support for artist, album, and other common metadata. AVRCP 1.4+ also allows artwork like album cover images to be displayed. So newer Android devices with AVRCP 1.4+ support can show full song details and artwork on compatible Bluetooth devices.

There are some caveats though. Some Bluetooth devices may only support a subset of metadata or have limited display capabilities. The Bluetooth MAP (Message Access Profile) version also affects what metadata can be displayed over Bluetooth. So even though a device supports AVRCP 1.3+, it may not be able to show all metadata if the MAP version is older. Proper metadata display requires both advanced AVRCP and MAP support.

Transferring Cover Art

The Android operating system supports the transfer of cover art images between devices via AVRCP. This feature allows the album cover, artist image or other associated artwork to be displayed on devices receiving the audio stream, such as in-car entertainment systems. It provides a richer media playback experience compared to just having the audio alone.

AVRCP 1.3 introduced support for cover art transfer in its Media Player Item attributes. This allows the cover art image file to be sent from the source device to the receiving device along with the audio track metadata. When a track changes, a new cover art image can be transferred and displayed.

For Android devices to send cover art via AVRCP, the source application must implement the necessary MediaSession and MediaMetadata APIs. The cover art needs to be embedded in the MediaMetadata. Once the artwork is added to the MediaMetadata, the Android system will transfer it automatically when streaming over AVRCP [1].

To display cover art on the Android device itself, the app must retrieve the images from MediaMetadata and render them in its UI. The system does not handle displaying cover art directly. Apps like music players will fetch the artwork and show it alongside the media playback screen.

So in summary, Android supports both sending and receiving cover art over AVRCP connections. To send artwork, it must be embedded in the MediaMetadata. To display artwork locally, apps need to extract it from MediaMetadata and render it appropriately. This provides a rich album art experience in Android apps and when streaming to other devices.

AVRCP Version History

The AVRCP Bluetooth profile has gone through several revisions over the years, with each version adding new features and capabilities. Here is an overview of the different AVRCP versions and what they offer:

AVRCP 1.0: The first version of AVRCP was released in 2003. It provided only basic remote control functionality for play, stop, pause etc. Metadata like song title, artist wasn’t supported.

AVRCP 1.3: Introduced in 2007, AVRCP 1.3 added the ability to retrieve metadata about the currently playing music track. This allowed remote devices to display song information.

AVRCP 1.4: Released in 2009, version 1.4 added album art transfer capabilities, allowing the cover art for the playing track to be displayed on the remote device.

AVRCP 1.5: Added in 2010, AVRCP 1.5 brought support for browsing media player playlists. Remote devices could now view and navigate playlists.

AVRCP 1.6: This 2016 update expanded AVRCP’s playback controls with options like seeking forward/backward in a track. It also added the ability to play queued media.

The key additions in AVRCP 1.3 and later have been metadata support, album art transfer, and advanced playback controls. These features enable remote devices to display track information and allow greater control over media playback.

Limitations and Issues

Despite its usefulness, AVRCP has some limitations and issues to be aware of:

Vendor Interoperability Problems: Not all Bluetooth devices implement AVRCP in the same way. There can be issues with interoperability between devices from different manufacturers, with some commands not working as expected. This is especially true for older versions of AVRCP.

Audio Quality Concerns: Bluetooth audio streaming using AVRCP has had issues with compressed audio quality in the past.Modern Bluetooth codecs like aptX have improved this, but there can still be quality loss compared to a wired connection.

Metadata and Art Support: Support for displaying metadata and cover art via AVRCP can be inconsistent across devices. iPhones in particular have had limitations for metadata transfer over Bluetooth due to Apple’s implementation.

Overall, while AVRCP is useful for controlling media playback, factors like vendor interoperability, audio quality, and metadata support should be considered when choosing Bluetooth products. Proper codec support and updated AVRCP versions help mitigate these limitations.

The Future of AVRCP

The latest version of AVRCP is 1.6, which was adopted in 2015. However, adoption of AVRCP 1.6 has been slow, with many devices still using the older 1.5 version.

One major addition in AVRCP 1.6 is support for cover art exchange through Bluetooth. This allows devices to show album artwork while streaming audio. According to one Reddit user, cover art exchange works well on their Samsung Galaxy Fold when connected to their car’s infotainment system (source). Wider adoption of AVRCP 1.6 will improve the media playback experience across devices.

Another expected improvement is deeper integration with voice assistants like Siri, Google Assistant and Alexa. Using AVRCP, voice commands could control media playback on remote devices. One possible use case is asking a smart speaker to play music on a Bluetooth speaker in another room.

AVRCP 1.6 also added some minor feature improvements like queue management, playback status and position synchronization between devices. Future versions may add support for streaming lossless audio codecs like LDAC. Overall, updates to AVRCP will focus on enhancing the remote control experience and media playback capabilities.