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Alternative A2DP Driver FAQ

Installation

Operating System
Windows 10/11 (x64 only). Please refer to the version history for officially supported Windows versions.
OS Boot Loader
Windows standard boot loader. (3rd party boot loaders are not supported)
Bluetooth Stack
Windows 10/11 inbox Bluetooth Stack. (3rd party stacks are not supported)
Administrator Privilege
Required when you install/uninstall the package and when you change the driver for each device.
Internet Access
Required when you retrieve the trial license and when you purchase the license.
  1. Download the installer from the download page.
  2. Double-click on the downloaded installer file and follow the instruction.

After installing the package to your PC following the "How to install the Alternative A2DP Driver package?" section, all of your Bluetooth audio devices are still controlled by the Windows inbox A2DP driver.

The next step is installing the Alternative A2DP driver to your audio device(s).

  1. Select the device in the left pane.
  2. Select "Alternative A2DP Driver" from the "Device Driver" drop-down list.
  3. Click on the "Install" button.
  1. Navigate to Windows Start Menu > Settings > Apps > Apps & features.
  2. Look for "Alternative A2DP Driver" in the App list.
  3. Click the button, then select "Uninstall" from the list.

After the trial period expires, your Bluetooth headphones will connect to your PC, but you don't hear any sound from them. You will also see an expiration message in the app.

In theory, as long as your Bluetooth adapter supports EDR (Enhanced Data Rate, 2/3Mbps data transfer), it should be ok. And, unless you are using a VERY old (like more than ten years old) adapter, it should support EDR.

That said, if you try very high bitrate (such as LDAC HQ, which uses more than x3 bitrate compared to the SBC and AAC), you will need to minimize the interference with other radio and Bluetooth traffics. Also, a high-power transmission (Class 1) adapter will help stabilize the streaming.

Please see another FAQ topic: How can I improve Bluetooth streaming stability? for the complete list of recommendations.

Back in the day, Windows' out-of-the-box Bluetooth support was very limited and did not include A2DP support. To use A2DP, you had to install a 3rd party driver. But, that's history. Windows 10/11 supports A2DP out-of-the-box, and you no longer need to install a 3rd party driver. More importantly, the 3rd party drivers used in the past are too old and not fully compatible with Windows 10/11 and shouldn't be installed.

If you see this message, it means that you have such an old A2DP driver installed on your PC. Please uninstall such driver before using Alternative A2DP Driver.

We cannot provide instructions on how to remove such a driver, as the necessary steps may vary depending on which 3rd party driver you have installed. If you don't know how to remove it, please find someone around you who can help you.

As the name suggests, the critical component of the Alternative A2DP Driver is a "driver" (a special software that can directly access hardware). Microsoft Store doesn't allow to publish a package that contains a "driver". Therefore, Alternative A2DP Driver cannot be distributed through Microsoft Store.

Purchasing a License

To purchase a license, please:

  1. Download and install the latest Alternative A2DP Driver to your PC.
  2. Open the application, click the “License Purchase” button, and select “Purchase license for this PC.”
  3. You will be redirected to the license file purchase page.
Screenshot of Alternative A2DP Driver app.

The type of license we currently offer is perpetual. You pay once and the license is valid forever.

IMPORTANT: This does not mean that the software is guaranteed to work with future versions of the operating system.

After completing the purchase process and verifying your payment, you will receive the license file via email or direct download. Once you receive the license file, please:

  1. Save the license file (which is attached to the email you received or included in the ZIP file you downloaded) to your PC's local disk.
    • Make sure that you do not modify it. Even the slightest modification will invalidate the license file.
    • Please save the license file in a safe place. You will need it when you re-install the program.
  2. Open the application, click the “License purchase” button, and select “Apply purchased license.”
  3. Select the license file you saved earlier in the "Open" dialog box.
  4. NOTE: Do not select the license file package (a ZIP file) that you downloaded directly from our website. You must first extract the license file from the ZIP file and select it.

  5. After applying the license file, you may need to disconnect and reconnect your headphones.
Screenshot of Alternative A2DP Driver app.

No. Since the license is tied to the unique ID of your motherboard, as long as you use the same motherboard, the license should remain valid. Similarly, changing the operating system version, replacing components such as video card, network card, Bluetooth adapter, and HDD/SSD will not affect the license.

However, please note that the new operating system must be one of the officially supported versions. Please check the version history to see which version of the Windows operating system is supported.

Please also note that if the motherboard is replaced, regardless of the reason for the replacement, the license is no longer valid and we will not issue a new license for the replaced motherboard. This includes the case of a motherboard replacement by your PC manufacturer.

No. The license is a single PC license. So, you need a valid license for each computer.

However, we do offer a discount for additional licenses. When purchasing a license for an additional computer, please use the "Discount for additional license" section of the license purchase page.

Unfortunately, the license is tied to the specific hardware (more specifically, to the motherboard) and is not transferable to another computer. This restriction applies regardless of the reason for replacing the hardware.

We wish we could make it transferable, but that would require a lot more resources (development effort and maintenance) and thus increase the license fee.

So we decided to keep it simple and instead offer a substantial discount on the replacement license. We hope this makes up for the lack of transferability. If you want to take advantage of this, please start the license purchase process from your new computer and look for the “Discount for additional license” section (bottom half of the license purchase page). The current price for an additional license is $1.99 (without AAC CODEC support) and $4.99 (with AAC CODEC support). We hope you will consider this a small fee for issuing a replacement license.

First of all, thank you for purchasing the license.

You should receive a license file in an email from support@bluetoothgoodies.com shortly after the payment is completed. If you do not receive the email within an hour, please:

  1. (If you paid with PayPal) Check the PayPal transaction status.
  2. Please check the email from PayPal or log in to your PayPal account and check the transaction status first. Sometimes the transaction remains in "pending state" for some time (up to a few days). If this is the case, we cannot issue a license until the status changes to "complete".

  3. Make sure you are looking at the correct mailbox.
  4. If you paid with PayPal, the license file will be sent to your PayPal account's email address. This may be different from the address you usually use. Please log in to your PayPal account and check your account profile if you are not sure.

  5. Check if the email was mistakenly marked as a SPAM mail.
  6. The vast majority (>99%) of the license delivery emails make it to the inbox. Unfortunately, some of them are misclassified as SPAM mail (this seems to happen more often with smaller email providers and self-managed email servers). So please be sure to check your Junk/SPAM folder before contacting us.

  7. If you don't find it in your Junk/SPAM folder, please contact us at support@bluetoothgoodies.com.
  8. Please be sure to:

    • Confirm and mention that you have checked your SPAM/Junk mail folder.
    • Send the email from the email address you used to purchase the license.
    • If you have another email address that we can reach (preferably with different email provider/domain), please mention that.
    • Usually, resending to the same address doesn't work well. If you have a different email address, this would increase the chance of successful delivery.

    We will get back to you as soon as possible. Please allow up to one business day for our response.

In some cases, the license delivery email bounces back (this usually happens if you misspelled your email address). If this happens, we will:

  1. Retry two more times to make sure that this is not a one-time error.
  2. And, wait for two days for you to contact us.
  3. If we cannot reach you in two days, we will cancel the license and issue a full refund.

Once this happens, we will refuse to sell the license to the same email address to avoid repeated failure.

If it has been less than two weeks since you purchased the license file, we can resend it to you free of charge. Please contact us from the email address where you used to receive the license file.

Otherwise, you can request to reissue a license for a small fee. Please start the normal license purchase process. Once you are on the license purchase page, please use the "Discount for additional license" section at the bottom half of the page. The current price for an additional license is $1.99 (without AAC CODEC support) and $4.99 (with AAC CODEC support).

Due to its dependence on external factors, such as:

  • The design of your headphones and Bluetooth dongle/adapter.
  • The sound playback software you use and how you use it.
  • The radio conditions around you.

We cannot guarantee that the Alternative A2DP Driver will work flawlessly for everyone.

Although we offer a 14-day refund window in case of a serious problem with the software, this does not cover the problems that can be easily found during the free trial period (such as the choppy sound) or the known issues/limitations mentioned in the "Limitations and Known Issues" section of the FAQ.

Please make sure you have thoroughly evaluated the software with each device you intend to use it with and that it meets your expectations before purchasing a license.

If, after purchasing a license, you encounter what you believe to be a software problem, please report it using the in-app feedback window.

Please note that once a refund is issued, the license is canceled. If we discover that a canceled license is being used, we will take appropriate action, including, but not limited to, refusing to do business with you again.

We accept payments through PayPal or Stripe (which accepts credit cards, debit cards, and selected wallets).

We realize that they don't cover payments from every country, but we have no immediate plans to add other payment methods, such as cryptocurrency.

Limitations and Known Issues

The current version (version: 1.5.0) has the following limitations.

  • Error recovery is minimal.
  • If something goes wrong during the CODEC configuration process, which usually happens when the device is connected, Windows recognizes the device is "connected", but the device does not work as an audio device.

    If this happens to you, please turn off the device, wait for the OS to recognize the device's disconnection, then turn it on and attempt reconnection. If the problem persists or occurs frequently, please send feedback using the in-app feedback page.

Multipoint is a wonderful feature that makes headphones useful when connected to multiple devices. However, we've seen that many headphones don't implement it properly, which causes problems especially when you try to use the headphones with high bitrate CODECs (such as LDAC and aptX HD).

Multipoint requires the headphones to constantly communicate with all connected devices. This includes pinging all devices while one device is streaming. The problem is that the headphones only have one transceiver to do this. So while the headphones are pinging the other devices, the streaming is briefly interrupted. This may not be a big problem if you are using low bitrate CODECs (such as SBC, aptX and AAC), but it can be a problem if you are using high bitrate CODECs or if your radio conditions are not good to begin with.

Some headphone manufacturers have noticed this problem and completely disable high bitrate CODECs when multipoint is enabled (Sony did this for their earlier products). Some only expose high bitrate CODECs to one of the paired devices. Others simply ignore the problem (or don't test enough to notice it) and make users suffer.

So, if you are experiencing any of the following problems with multipoint-enabled headphones:

  • You cannot select high bitrate CODEC while other device can.
  • Unstable connection (such as choppy sound and dropped connections).

Please try the following to see if this is caused by an improper multipoint implementation.

  1. Unpair the headphones from your PC.
  2. Factory reset your headphones. (Please refer to your headphone manual for instructions.)
  3. If your headphones have a setting to enable/disable multipoint feature, please disable it.
  4. Pair the headphones to your PC.

If the problem is resolved, please continue with the following steps:

  1. If you have previously turned off the multipoint feature, turn it back on.
  2. Un-pair from and pair with other device (such as a smartphone). Old pairing information is obsolete after you reset your headphones to factory defaults.

If the problem returns, it means that the problems are caused by improper implementation of multipoint in your headphones. Please contact your headphone manufacturer to see if they have a solution.

ASUS AI Noise Canceling only works when both speaker and microphone audio streams go through specific path. Using a third-party A2DP driver such as Alternative A2DP Driver breaks this assumption and causes ASUS AI Noise Canceling (and similar software) to malfunction.

As you can see in the app's user interface, there are many options for A2DP CODEC configuration. All devices that claim compatibility with A2DP specification have to implement those options properly, and the manufacturers should test whether those options work before they ship the devices.

But, historically, PCs and phones used only one setting (44.1 kHz sampling frequency, Joint Stereo, block size 16, loudness allocation, eight subbands), and the device vendors never tested their products with other settings. I suspect many of them don't even have a way to test their devices. So, you are probably the first person to try different configurations, and there's a good chance you will find out they are not working.

If you encounter the issue, please try the following:

  • Click on the "Load safe parameters for the CODEC" button and load the most commonly used parameters.
  • Turn the device off, then on, and reconnect.
  • Check if the device is working correctly.

If the device works with the safe parameter and has a problem with others, it's most likely an issue with the device. Please DO NOT report such an issue unless you have a good reason to believe that this is a driver issue. When you report such an issue, please include:

  • The reason why you think/suspect this is a driver issue, and
  • Mention that you've read this FAQ.

This will help your feedback to get the proper attention.

Both Windows Sonic for Headphones and Dolby Atmos for Headphones support only a limited wave format. (This is a limitation of each spatial sound implementation, not a limitation of the Alternative A2DP Driver.) For example, as of this writing in February 2023, Dolby Atmos for Headphones (Windows 10 version) does not support 88.2/96 kHz formats.

Therefore, if you need to enable this feature, be sure to select the formats supported by each spatial sound implementation.

How a Bluetooth Headset Works

Before discussing the limitations of the Bluetooth headsets, it is important to understand how today's Bluetooth headsets work.

As the diagram above shows, audio streams are handled by two separate profiles. One is called HFP (Hands-Free Profile) and is used for communication audio (e.g., video conferencing, interactive gaming). This profile provides bidirectional audio channels (speaker and microphone). But they are monaural, and their quality is not so good.

The other, called A2DP (Advanced Audio Distribution Profile), can handle stereo audio with good sound quality. But it supports only one direction.

Bluetooth Headset Limitations

In theory, these two profiles are independent and can be used simultaneously. But, in reality, most, if not all, Bluetooth headsets on the market today do not support the simultaneous use of the HFP and A2DP profiles. There is a "switch" (the part highlighted with a yellow box) in the headset, and it only plays the sound from one of them (it is a "switch", not a "mixer").

As a result, the following limitations apply regardless of which driver/OS you are using:

  • To use the microphone, you have to send the playback audio through the HFP profile (using the "Headset Speaker" endpoint), and the audio will be monaural.
  • If you try to send data through the A2DP profile while the microphone is in use (i.e., HFP is active), the data may be sent to the headset, but the headset will ignore it.

  • To hear the stereo audio, you have to send the data via A2DP (using the "Headphone Speaker" endpoint). And you have to make sure that no other application is using the "Headset Speaker" and "Headset Microphone" endpoints.

Starting with version 1.2.0, the Alternative A2DP Driver configuration app displays the following message in the Current Status section.

If you see this message, it means that HFP is active because:

  • One of the running applications accessed the microphone of the headset, or
  • One of the running applications opened the "Headset Speaker" endpoint.

And as a result:

  • You hear a low-quality monaural sound, and
  • You do not hear the sound streamed to the "Headphones Speaker" endpoint.

Windows 11 "Unified Audio Endpoint" Feature

Confused? You are not alone. Many people have had trouble in configuring the video conferencing programs properly, and Windows 11 has come up with a solution called "Unified Audio Endpoint". Instead of exposing two playback endpoints ("Headphones Speaker" and "Headset Speaker"), it exposes only one unified "Speaker" endpoint to the user. It then dynamically redirects the stream to either the "Headphone Speaker" or "Headset Speaker" endpoint, depending on the state of HFP.

This relieves the user of the burden of selecting the correct endpoint. But don't forget that the underlying limitation is still there. When using the microphone, you are still forced to use a monaural speaker, and the sound quality is not good. This is a hardware limitation and cannot be solved by software.

As of this writing in July 2023, 360 Total Security (360安全卫士) erroneously claims that the Alternative A2DP components are Trojan horse viruses and deletes them. As a result, you may experience various problems.

Symptoms include:

  • Switching from the Windows standard driver to the Alternative A2DP Driver fails.
  • Already installed Alternative A2DP Driver suddenly stops working.
  • Volume control stops working.

If you are affected by this problem, please:

  • Decide whether you trust our software or not.
  • If you trust our software, please instruct 360 Total Security not to delete any files or modify any driver/service settings related to the Alternative A2DP Driver.
  • Then uninstall and reinstall the entire Alternative A2DP Driver package.
Problem

Windows allows you to select the format (the combination of bit depth, sampling frequency, and number of channels) that the device uses in shared mode. However, when the Windows 11 Unified Audio Endpoint feature is in effect, your choice of the default format is ignored.

Cause

This is a limitation (or a bug, depending on how you look at it) of the Windows 11 Unified Audio Endpoint feature. When this feature is in effect, the Windows audio subsystem simply assumes that the device supports only one format. This is true if you are using the Windows standard A2DP driver, but may not be true for third-party drivers, including the Alternative A2DP Driver. As a result, Windows chooses the first format from the list of formats provided by the driver. In the case of the Alternative A2DP Driver, it is the most Hi-Fi format (with the most channels, highest bit depth, and the highest sampling frequency).

Please note that this is an issue with the Windows 11 Unified Audio Endpoint feature. If you are using Windows 10 or a device that only supports A2DP (without HFP support), the Unified Audio Endpoint feature is not in effect and you will not have this problem.

Workaround

If you are using the device in shared mode:

Instead of enabling multiple formats in the driver and letting Windows select one of them, enable only one format (using the Alternative A2DP Driver Configuration program) and force Windows to use that format.

If you are using the device in exclusive mode:

You are not affected by this problem. You can enable as many formats as you like. It's up to your media player application to choose which format to use.

AAC CODEC License

The AAC CODEC technology is patented and the use of this technology requires the payment of patent royalties.

On the other hand, many Alternative A2DP Driver users don't need AAC CODEC support (they use other CODECs like LDAC or aptX-HD) and we don't want to force them to pay for the AAC CODEC. So we made two editions of the licenses. One is without AAC support (the same licenses we've been offering since day one). The price of this license is the same as before. The other is the one with AAC CODEC support. It is slightly more expensive than the first one to cover the royalties. We also provide an upgrade path from "without AAC CODEC support" to "with AAC CODEC support".

  1. Make sure you have the Alternative A2DP Driver version 1.4.0 or higher.
  2. Make sure you have installed your license (without AAC support).
  3. Make sure your PC is connected to the Internet.
  4. Select "About" in the navigation (left) pane (①).
  5. Click the "Start free AAC CODEC trial" link (②).

If you purchase the license upgrade from "without AAC" to "with AAC", your new license will replace your old license. You can activate the software with the new license and you will not need the old license anymore.

If you don't know if you need it, it's probably unnecessary, but here are a few things you should know:

  • Windows 10 standard A2DP driver doesn't support AAC CODEC.
  • So if you're using Windows 10, your headphones support AAC CODEC, and you want to make use of it, you can use the Alternative A2DP Driver's AAC CODEC support.

  • Windows 11 standard A2DP driver DOES support AAC CODEC.
  • Its support is basic (for example, the sampling frequency is fixed at 48kHz), but it works reasonably well. So if you don't need advanced features (such as dynamic sampling frequency switching), you don't need the Alternative A2DP Driver's AAC CODEC support.

  • You can purchase a license without AAC CODEC support for now, and later, if it becomes necessary, you can upgrade to the "with AAC CODEC support" edition.

Troubleshooting

Alternative A2DP Driver asks your A2DP device about its supported CODECs and determines which CODEC is selectable based on the device's response. If a specific CODEC is not selectable, it means that your device reported that the CODEC is not supported.

If you think that the unselectable CODEC should be selectable:

  1. Please check the device's official specification.
    • If your device can act as both a transceiver and a receiver, be sure to check the supported CODEC in its receive mode. Your device may have a different set of CODECs for transmit and receive modes.
    • Please note that there is no compatibility between the aptX CODECs (aptX, aptX-HD, aptX Low Latency, and aptX Adadaptive). Therefore, the fact that your device supports aptX Adaptive does not necessarily mean that it supports aptX-HD or aptX Low Latency. Please refer to another FAQ for more details.
    • Also keep in mind that some (often smaller / lesser known) vendors advertise their products with inaccurate CODEC information.
    • LHDC (from Huawei/Savitech) is different from LDAC (from Sony), and it's not supported by the Alternative A2DP Driver (see another FAQ for more information).
  2. Please understand that your device may dynamically change the supported CODECs for various reasons.
  3. Here are some examples.

    • Some devices have a mode that prioritizes connection stability.
    • For example, many Sony headphones have "Prioritize Sound Quality" and "Prioritize Stable Connection" modes. Different manufacturers may use different names, but high bitrate CODECs (such as LDAC and aptX-HD) are often disabled in "Prioritize Stable Connection" mode. These settings are usually controlled by the manufacturer's phone apps, but they may be changed by direct operation on the headphones and you may have accidentally selected the "Prioritize Stability Connection" mode.

    • Some devices disable high bitrate CODECs (such as LDAC and aptX-HD) based on pairing/connection state.
    • As explained in another FAQ, implementing multipoint (the feature that allows the device to connect to two host devices simultaneously) while supporting high bitrate CODECs requires careful design of the device, and not every manufacturer has the know-how to do it right. In fact, even Sony made multipoint and LDAC mutually exclusive when they introduced multipoint to their products. But they eventually improved their multipoint implementation, and newer versions of their firmware allow users to enable both.

      Other manufacturers are no better than Sony, and many devices still have this limitation. The exact way the limitation works varies from device to device, but the common patterns are:

      • High-bitrate CODECs are disabled when multipoint feature is enabled.
      • High-bitrate CODECs are enabled only for the primary (first paired) host device and disabled for other (second and later paired) host devices.
      • High-bitrate CODECs are disabled when the device is connected to multiple hosts simultaneously.
  4. AAC support may be limited by the license you have.
  5. Due to patent licensing restrictions, AAC support in the Alternative A2DP Driver requires a "with AAC support" edition license. If you have purchased a "without AAC support" edition license, you cannot select AAC, even if your device supports AAC CODEC.

In summary, except for the last case (AAC support), if the CODEC is not selectable in the pull-down menu, it just reflects what your device can support in its current state. If you think this is wrong, please contact the manufacturer of your device. This is a device issue and we cannot provide support.

Old Sony firmware did not enable LDAC when multipoint is enabled.
Many non-Sony devices have similar problem.

Under ideal conditions (no transmission errors/retransmissions), Bluetooth can theoretically transmit up to ~1.5Mbps of streaming data (assuming all time slots are filled with 2-DH5 packets). In reality, however, radio signals are distorted by interference and data needs to be retransmitted. As a result, the effective bitrate is much lower. If you try to use high bitrate CODEC settings (such as SBC with a bitpool higher than the device's maximum bitpool, aptX-HD, LDAC with HQ quality), you may be sending more packets than your setup can handle. As a result, you may experience the following problems:

  • Choppy sound.
  • Audio latency increases over time.
  • Connection may be lost unexpectedly.
  • The right/left sound of the TWS headphones may be out of sync.

If you are experiencing these symptoms, you may need to check the following factors:

  1. Minimize radio interference to reduce the retransmission
    • Do not use 2.4GHz radio, such as 2.4GHz WiFi
    • Use 5/6GHz WiFi or wired Ethernet instead.

    • If you have to use 2.4GHz WiFi, consider using a WiFi/Bluetooth combo adapter instead of separate adapters
    • WiFi and Bluetooth adapters communicate with each other and minimize interference in a combo adapter. They do not communicate with each other if you use separate adapters and cause more interference.

  2. Use high transmission power Bluetooth adapter
  3. Bluetooth devices are classified into three power classes. Most Bluetooth adapters used for PC are either Class 1 (high power) or Class 2 (medium power). A Class 1 adapter gives you a more stable connection at a high bitrate. As of this writing, there is no easy way to tell if your adapter is Class 1 or Class 2, but here is a rule of thumb:

    • Most integrated (the adapters integrated into the laptops and the desktop's m2 slot) adapters are Class 1.
    • External USB dongles are a mix of Class 1 and Class 2 (unless advertised as Class 1, the chance is it's Class 2). Please check with the manufacturer of the adapter.

  4. Maximize the time slot used by other Bluetooth devices
  5. If you connect other Bluetooth devices, such as a keyboard, mouse, and touchpad, they eat up the time slots that can be used for audio streaming. The amount of data those devices send is relatively small, but their impact is not negligible as they send the data frequently.

    Those devices may need to be turned off while high-bitrate audio streaming is happening to free up the time slots usable for audio streaming. (Or, if you use the high-bitrate audio streaming regularly, you may want to consider switching to the mouse/keyboard that uses non-Bluetooth wireless technologies.) Please note that those devices still consume timeslots while they are idle as long as they are connected to your PC.

  6. TWS specific issues
  7. Last but not least, TWS headphones are not good at receiving high-bitrate streams. You usually start hearing choppy sounds at a lower bitrate compared to regular headphones. This is because:

    • Due to their smaller size, they don't have good antennas. It causes more data corruption and ends up with more re-transmission.
    • Earbuds need to communicate with each other, and that is done using the Bluetooth time slots otherwise used to receive the streaming packets.

    For example, LDAC HQ (990kbps) with TWS is not impossible, but for that to work without choppy noise, you need to clear all other issues listed above.

  8. Multipoint
  9. If multipoint is properly implemented, the connection of another device should have little effect on the stability of the streaming. However, some headphones do not properly implement multipoint, and the activity between the headphones and another device (even if it is a seemingly small activity) can significantly limit the maximum bitrate of the streaming. You may not notice this problem if you are streaming at a low bitrate (such as ~300kbps), but it can be a significant problem if you are streaming at a high bitrate. To see if this is the case, please do the following:

    1. If the phone app for your headphones has an enable/disable control for the multipoint feature, disable it. (preferred method)
    2. Otherwise, turn off the Bluetooth radio on the other device.

    and see if this improves streaming stability. If it does, it means that your headphones' multipoint implementation is not optimal. Your choice is to either avoid multipoint or reduce the bitrate/encode quality mode (manually or automatically by enabling ABR).

  10. Device driver for the Bluetooth adapter (dongle)
  11. Sometimes the device driver of the Bluetooth adapter can affect the streaming stability. Apparently, because the standard Windows A2DP driver only uses up to ~300kbps bitrate, adapter drivers are only tested with such low bitrates. They may have problems with higher bitrates like 990kbps. And in our experience, newer versions aren't always better than older ones.

    So please start with the latest driver version. If it doesn't work well, please try some older versions. Please also note that Bluetooth adapter drivers are often automatically updated by the Windows Update. So if you find a driver version that works well for you, please keep it. You may want to reinstall it later.

If the problem persists after checking all of the above, you probably need to change the CODEC settings to lower the bitrate.

Features

aptX Adaptive/Lossless

We currently have no plans to support these variants of the aptX CODEC family due to patent/licensing reasons.

The following Reddit topic explains Qualcomm's licensing policy for the aptX CODEC family:
Qualcomm has open sourced its aptX and aptX HD encoders, making them freely available to Android OEMs. Here's what that means.

LC3 CODEC / LE Audio

As of June 2023, LE Audio is already supported by Windows 11. For Windows 10, adding support for LE Audio would require replacing the entire Bluetooth stack, and that's a huge and risky task.

So, there's no plan to do anything about LE Audio in the Alternative A2DP Driver.

Other CODECs (including SSC and LHDC)

No plans for other CODECs, because as far as we know they are neither open source (like SBC, LDAC, aptX and aptX-HD) nor licensed to third party developers (like AAC).

If you have information about the licensing of other CODECs, please let us know.

We are aware that there is a GitLab repository called "Savitech LHDC Codec for AOSP", but as far as we know they're not part of AOSP (as of this writing in 9/2023).

Unlike other CODECs, the bitrate of AAC CODEC's bitrate is limited by the design of the device (more specifically, the MTU of the streaming L2CAP channel) and the sampling frequency. The current version of the Alternative A2DP Driver uses the maximum bitrate your device allows.

Although there's no way to increase the bitrate beyond that, it is possible to go lower than the limit (possibly, for longer battery life, more stable connection, etc.). If there are such needs, please let us know. If there are enough requests, we may consider adding a control to lower the bitrate.

No, this driver currently only supports only A2DP source role (i.e. streaming from your PC to headphones/headsets/speakers).

For A2DP sink role, you need to use Windows 10 (build 19041 or later)/11 standard A2DP driver.

Usage Hints

One of the reasons why you hear the stuttering/choppy noise is the high rate of data re-transmission between your PC and headphones due to the poor radio condition. When there is too much re-transmission, some media packets are not received by the headphones on time, and as a result, you will hear stuttering/choppy noise.

One of the solutions for this issue is to reduce the amount of media data that needs to be transmitted (by slightly decreasing the audio quality). Please move the "Bitpool" slider to the left (decrease the bitpool value) while you are playing audio and see if the noise is reduced.

There are two ways to increase the bitrate of SBC CODEC.

Method 1: Use Dual Channel mode instead of Joint Stereo mode — Guaranteed to work by the A2DP specification, but not so efficient

The first way is to use the Dual Channel mode instead of the commonly used Joint Stereo mode. Due to the peculiarity of how the A2DP specification is defined, a device that supports maximum bitpool N (this bitpool number is assigned to combined left and right channel) is required to support the same maximum bitpool number N in Dual Channel mode, where each channel is encoded into that bitpool N. So, the resulting bitrate will double if you use the Dual Channel mode. Sounds too good to be true? Of course, there is a catch. Because the Dual Channel mode encodes the right and left channels independently without taking advantage of the correlation between the channels, it cannot compress the data as efficiently as the Joint Stereo mode. For example, when you compare Joint Stereo mode at bitpool 2 * N and Dual Channel mode at bitpool N, they yield (almost) the same bitrate, but the Joint Stereo will sound better.

Please also note that if you switch from Joint Stereo to Dual Channel without changing the bitpool number, the resulting bitrate may be too high to transmit stably due to the error and re-transmission.

Method 2: Use Joint Stereo mode with a higher bitpool number — May work with many, but not all headphones

The other way to increase the bitrate is to simply increase the bitpool number while still using the Joint Stereo mode. Most devices limit the maximum bitpool number to 53 (or even lower), but some allow a higher bitpool number. If your device is one of them, you can safely increase the bitpool number (slide to the right) and see how far you can go.

For the devices with a maximum bitpool number of 53 or lower, the Alternative A2DP Driver provides an option to override (ignore) that limitation and let you try a higher bitpool number.

WARNING: There is no guarantee that this option works (and, in theory, there is even a possibility that it might cause damage to your headphones if their firmware is poorly written), but if you want, you can try the "Override device's Max Bitpool limitation" option at your risk.

Windows inbox A2DP driver supports only 44.1 kHz sampling frequency for SBC CODEC. So, if you listen to the contents encoded with 48 kHz sampling frequency, you are forced to down-sampling.

On the other hand, Alternative A2DP makes all sampling frequencies supported by your audio device available to the media player app. So, if the media player app can dynamically switch the sampling frequency based on its source, you can eliminate the audio quality loss due to the down-sampling.

Please follow the instructions below to enable this feature.

Alternative A2DP Driver setting

First, you need to configure the Alternative A2DP Driver to use both 44.1 and 48 kHz sampling frequencies.

It is recommended NOT to enable other sampling frequencies (i.e., 16 and 32 kHz) unless you really want to use them.

(optional) Verify the above setting is working

  1. Connect your Bluetooth audio device to your PC.
  2. Type mmsys.cpl into the Windows search box and hit ENTER to start the legacy Sound control panel.
  3. Select the Playback tab (which should be selected by default), look for the Bluetooth audio device, and double-click on it to open the Headphones Properties dialog box.
  4. Select the Advanced tab and check the drop-down list in the Default Format section. You should see "2 channel, 16 bit, 44100 Hz (CD Quality)" and "2 channel, 16 bit 48000 Hz (DVD Quality)". If you do, the driver is working fine.
  5. NOTE: This drop-down list is supposed to let the user select the audio stream format when this audio device is used in the Shared Mode, but it does not seem to be working on recent Windows 10 and 11. The cause is unclear at this point, but it seems to be an issue with Windows 10 and 11.

Media player app setting

The media player app has to support the Exclusive Mode (and please note that not all media app does) so that it can change the sampling frequency of the audio device. (When the device is used in the Shared Mode, the sampling frequency is controlled by the System Mixer, and media player apps cannot control it.) Please also note that, by definition, in the Exclusive Mode, your audio device is exclusively controlled by that media app, and the output from other apps (including the system sounds) cannot be played on the same device.

Following are some of the apps that support Exclusive Mode and how to configure them for the dynamic sampling frequency change.

Kodi

  1. Navigate to the "Settings" > "System" > "Audio" page.
  2. Set the settings level (at the bottom-left corner) to "Advanced" or above.
  3. Select "WASAPI: Headphones (...)" or "WASAPI: default" for the "Audio output device."
  4. Select "Best match" for "Output configuration" (this setting item does not show if the setting level is "Basic" or "Standard").

MPC-BE

  1. Navigate to the "View" menu > "Options ..." to open the "Options" window.
  2. Select the "Audio" node in the left pane.
  3. Select "0. MPC Audio Renderer" for the "Audio renderer" drop-down list.
  4. Click the "Properties" button to open the "Properties" dialog box.
  5. Select "Exclusive" for the "WASAPI mode" drop-down list, and enable the "Allow bit exact output" checkbox.

MPC-HC

  1. Navigate to the "View" menu > "Options ..." to open the "Options" window.
  2. Select the "Playback" > "Output" node in the left pane.
  3. Select "MPC Audio Renderer" for the "Audio Renderer" drop-down list.
  4. Select the "Internal Filters" > "Audio Renderer" node in the left pane.
  5. Click the "MPC Audio Renderer Settings" button to open the "Properties" dialog box.
  6. Select "Exclusive" for the "WASAPI mode" drop-down list, and enable the "Allow bit exact output" checkbox.

No. You only need to run the application when you want to change the configuration or check the status of the driver. Otherwise, you don't need to open it.

General Information

Here's the list of the links to some of the information.

First of all, as with any CODEC, there is no direct compatibility between two different CODECs. For example, the audio stream transmitted by your PC using the aptX-HD CODEC cannot be received by a device that doesn't support aptX-HD, even if the device supports other aptX series CODECs such as aptX or aptX Adaptive. This is the way CODECs work in A2DP.

Qalcomm, the company behind aptX technology, claims on their website (https://www.aptx.com/aptx-adaptive [snapshot from Feb. 2024]) that aptX Adaptive is "compatible with aptX and aptX HD", but that's a very misleading statement. What the statement really means is:

  • Devices that implement aptX Adaptive should also implement aptX and (in some cases) aptX HD.
  • Unfortunately, this rule is not strictly enforced. aptX is supported by most (but not all) aptX Adaptive devices, but aptX HD is not supported by many aptX Adaptive devices.

  • There is no mention of aptX Low Latency. Therefore, support for aptX Low Latency is up to the design of each device (and many devices do not support it).

So if you don't see any of the aptX series CODECs disabled in the CODEC Type list of the Alternative A2DP Driver Configuration program, it just means that your headphones don't support the aptX series CODEC you want to use. If it's against the rule defined by Qualcomms, please contact the manufacturer of your headphones.