Why is there audio delay?
Xbox, Apple TV and PC deliver Dolby Digital as PCM51 and Dolby Atmos in MAT format. Many new TVs can handle that. However, when a soundbar or an AV receiver is connected to the television, the sound is often delayed. This is called audio delay. But why is that?
The audio formats PCM5.1/7.1 and Dolby-MAT (Dolby Atmos) cannot be transmitted via HDMI-ARC. This interface is not defined for this and the data rate is too high. This only works with HDMI-eARC. If your sound system has HDMI-ARC only, the TV still outputs sound, but has to transcode it. So PCM51 becomes Dolby Digital Bitstream, Dolby Atmos becomes Dolby Digital Plus. This takes time and results in the delay in the output. The sound system then has to decode the sound again.
If the player recognizes that a sound system is connected and the television or sound system only has an HDMI-ARC interface, the output is adjusted. With Playstation or Xbox you can choose the output format manually. The 5.1 sound can be delivered as DTS or Dolby Digital Bitstream. The time delay for encoding and decoding is higher with Dolby Digital. So DTS would be faster, but many televisions do not let it through.
What possible solutions are there?
As described, the bottleneck is the HDMI-ARC interface. However, even 10-year-old AV receivers have no problems processing HD audio formats on their HDMI inputs. That's why we have the eARC adapter VAX01202 designed. The HDMI-eARC audio signal from a modern TV is converted to a normal HDMI signal. A black screen is added to this signal, so it can be processed at a standard HDMI input. The DVD player or AUX HDMI input on the AV receiver, for example, is suitable for this. The TV sound comes from now on via this input and no longer via "TV".
The advantage of such a solution is that the player remains directly connected to the television. This means that modern HDMI 2.1 functions such as VRR and ALLM with 4K 120Hz can be used - even if the good old AVR does not support it. So it is a good solution to reduce the audio delay for gamers with Xbox Series X or PC.
Most AV receivers support control via HDMI CEC via their HDMI inputs. As a result, the volume of the sound system can be controlled as usual with the TV remote control, and muting also works. Due to the principle, it is not possible to switch on all connected devices automatically.
However, a soundbar with a single HDMI connection cannot be used with the VAX01202. Because such a connection is an HDMI output and not an input. Only the audio return channel (HDMI-ARC) from a television can be processed via it. This solution is therefore not possible for such a soundbar with a limited HDMI-ARC interface.
