Bluetooth headphones are now widely used, as many new smartphones have no connection for wired models. The more often occurs a problem: the sound during video streaming does not come perfectly synchronously in the headphones. Even minimal delays are perceived as a viewer. This bothers especially with music videos and film dialogues, if the sound to mouth movement just does not fit. This is called the delayed lip sync.
Therefore, the sound is asynchronous with Bluetooth headphones
The main reason for the delayed transmission of the sound to the headphones is often an outdated Bluetooth standard, but also the complicated transmission of the sound, especially in true wireless in-ears. In addition, the video source – so for example, the YouTube app, the browser or an old smartphone – be the cause.
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Because the reasons for the audio delay can be diverse and also depend on software and the compatibility of the devices with each other, even well-known headphone manufacturers like Bose have a problem with it. So after many customer complaints Bose had to deliver a software update for his first True-Wireless-In-Ears “SoundSport Free”. Even with the 1st generation AirPods, we found an audio delay when streaming video through the YouTube app on an iPhone XR. And even the new Huawei FreeBuds Lite did not always reproduce the sound in lip sync.
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But why is that exactly?
To illustrate the complexity of the problem, we break down the transmission path for different types of headphones. In principle applies: The more complex the signal transmission, the longer it takes until the sound arrives in the ear and that leads in the end to the perceived time delay.
Wired headphones – four steps
Simple packaging with little content: For 15.99 euros, there is not even a user manual at Amazon’s Sport-In-Ears-but not bad, because that saves resources. And thanks to simple cable connection, there is guaranteed synchronous sound during video playback.
Digital audio signal from the source (smartphone, computer) → conversion from digital to analog (DAC) → forwarding to the amplifier → transmission of the signal through the cable to the headphones and thus to the ear
Conclusion: simplest transmission, no synchronization problems
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Bluetooth headphones – eight steps
The new noise-canceling headphones Sony WH-1000MX3 have the latest Bluetooth transmission standards and thus pose no problems with the synchronous sound reproduction
Digital audio signal → coding → Bluetooth transmitter sends the encrypted signal → Bluetooth receiver in the headphones receives the encrypted signal → decoding → conversion from digital to analog (DAC) → forwarding to the amplifier → transmission to the headphone membranes and thus to the ear
Conclusion: The Bluetooth standard is the deciding factor here. The older and worse the Bluetooth technology, the longer the coding, transmission and decryption of the signal takes.
True Wireless In-Ears – Nine Steps
Huawei’s FreeBuds Lite are so-called True Wireless In-Ears, making it particularly complex in terms of sound transmission. Because of this, in some scenarios, non-synchronous sound reproduction occurs during video watching.
Digital audio signal → coding → Bluetooth transmitter sends the encrypted signal → Bluetooth receiver in the headphones receives the encrypted signal → decoding → NFMI chips transmit the signal from one in-ear to another – Conversion of the signal from digital to analogue in each in-ear (DAC) amplifier in each in-ear transmission of the signal to the membranes and thus to the ear
Conclusion: With True Wireless In-Ears, the biggest risk is that the sound will not be transmitted in sync with the video. Because not only the Bluetooth standard is crucial here, but also the NFMI chips, which transmit the signal wirelessly from one in-ear to the other.
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You should pay attention to this with Bluetooth headphones
Tip 1 – Pay attention to the Bluetooth wireless standard.If you decide to buy a new Bluetooth headset, it should have the latest Bluetooth 5.0. But you only benefit from faster and better data transfer if your source device (smartphone, tablet, computer) also has the latest Bluetooth standard. Otherwise it is always transmitted in the slower of the two versions.
Tip 2 – Pay attention to the support of the sound codes AptX, AptX HD.Both provide excellent audio quality and low latency. It is even better if the headphones are the latest versionsAptX Low Latency or AptX Adaptivesupported. These provide the least delay in sound transmission. They are especially suitable for gamers.
Unfortunately, iPhones, iPads and AirPods from Apple do not support the AptX standards, but rely on a so-called AAC codec, which is also integrated by other manufacturers such as Bose and Sony among many other codes.
Tip 3 – Avoid devices (both sources and headphones) that only support the outdated SBC Bluetooth standard.
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Tip 4 – When buying new Bluetooth headphones, test whether you can play the sound, especially from YouTube, Netflix, and Amazon Prime Video without any noticeable delay.If both the source device and the headphones meet the criteria mentioned in Tip 1 and 2 and there are still problems, it can only be a headphone error. Some manufacturers can fix this with a software update, like Bose on his SoundSport Free In-Ears.
If you notice such a problem, it is best to contact the manufacturer’s customer service. If he can not fix the asynchrony, you may have to choose a different model. Keep in mind, however, that an outdated Bluetooth standard in your source device may be the cause of the delayed sound reproduction.
Tip 5–Another reason for the audio delay may be the app used or the streaming portal.Here you should make sure that you use the latest versions of apps and programs. In addition, sometimes small tricks help. Especially with Apple devices, for example, videos are played better on the Safari browser than, for example, in Google Chrome. If you have an audio delay in the YouTube app, then get the video in the Safari browser. That can bring a significant improvement.