What Is the BK-21AC?
The OREI BK-21AC is an 8K 2 input HDMI switch with audio extraction. It allows you to connect two HDMI source devices to one TV, monitor, or projector while also extracting audio through Optical or 3.5mm stereo output.
It is useful when your display has limited HDMI inputs, but you want to connect two devices such as a PlayStation, Xbox, Blu-ray player, PC, streaming device, Roku, Fire TV, cable box, or media player.
The BK-21AC supports HDMI 2.1, HDCP 2.3, with a video bandwidth of 48Gbps, and video resolutions up to 8K@60Hz, 4K@120Hz, and 1080p@240Hz. It also supports HDR10+, Dolby Vision, CEC, advanced EDID management, and audio extraction through Optical and 3.5mm outputs.
IMPORTANT — BK-21AC Is NOT a Seamless HDMI Switch
The BK-21AC is not a seamless switch.
This means that when you switch from one HDMI input to the other, your display will usually show a black screen for a moment while the HDMI signal reconnects.
This is normal. The TV, monitor, or projector needs time to detect the new HDMI source, complete the HDMI handshake, and show the image again.
In most setups, the black screen may last a second or two. In some cases, it may take longer depending on:
- The TV or monitor being used
- The resolution and refresh rate
- HDMI cable quality
- The HDMI source device
- Whether 8K@60Hz, 4K@120Hz, HDR, VRR, or Dolby Vision is being used
The BK-21AC switches between HDMI sources, but it does not provide instant or zero-delay switching.
IMPORTANT — Auto Switching Depends on HDMI 5V Signal Detection
The BK-21AC supports auto switching, but it works by detecting the 5V signal from the connected HDMI source.
In simple terms, the switch looks for which HDMI source appears to be active.
If one source is connected and then another source is plugged in or powered on, the BK-21AC may automatically switch to the newly detected source.
However, many modern streaming devices do not fully turn off. Devices such as Apple TV, Fire TV Stick, Google Chromecast, Roku, and similar media players often go into standby mode instead of shutting down completely. Even in standby, they may continue sending a 5V signal through the HDMI cable.
Because of this, the BK-21AC may still detect that device as active even when the customer thinks it is off.
For example:
If Apple TV is connected to Input 1 and PlayStation 5 is connected to Input 2, the BK-21AC may switch to Apple TV when the PS5 is turned off because Apple TV is still sending an HDMI 5V signal.
But when the PS5 is turned back on, the BK-21AC may not automatically switch back to the PS5 because Apple TV never fully stopped sending its HDMI signal.
In this type of setup, use the front-panel Select button or included remote to switch manually.
IMPORTANT — Audio Extraction Depends on the Audio Format
The BK-21AC can extract audio through Optical and 3.5mm output, but the audio format must match the output you are using.
The 3.5mm stereo output supports stereo audio only. If you are using the 3.5mm output, set the source device audio output to PCM or Stereo.
The Optical output supports compatible digital audio formats such as PCM and Dolby/DTS 5.1 formats.
If the audio format from the source is not compatible with the audio output or connected audio device, you may not get sound from the Optical or 3.5mm port.
Ports and Panel Layout
| Port / LED / Button | Location | Function |
| Power Button / Remote Power | Front / Remote | Turns the switch on or off |
| Input 1 / Input 2 Buttons | Remote | Selects the corresponding HDMI input |
| IR Button | Remote | Turns IR receiving function on or off |
| Auto Button | Remote | Turns automatic switching on or off |
| Micro USB | Front panel | Used for firmware upgrade |
| Power Indicator | Front panel | Lights up when active power is received |
| Output Indicator | Front panel |
Lights up when the output is connected to an active display |
| Input Indicators 1/2 | Front panel |
Lights up when the corresponding input is connected to an active source |
| Auto LED | Front panel | Lights up when automatic switching is enabled |
| IR LED | Front panel | Lights up when IR control is enabled |
| IR Receiver | Front panel | Receives signal from the included remote |
| Select Button | Front panel | Press once to switch to the next input source |
| EDID DIP Switches | Front panel | Used to change EDID modes |
| HDMI Input 1/2 | Rear panel | Connect HDMI source devices |
| HDMI Output | Rear panel | Connect to a TV, monitor, or projector |
| Stereo Output | Rear panel |
3.5mm audio output for speakers, headphones, amplifier, or stereo input |
| Digital Output | Rear panel | Optical audio output for soundbar, AVR, or amplifier |
| DC 5V | Rear panel | Connect the included power adapter |
Step-by-Step Setup
- Connect your first HDMI source device to HDMI Input 1.
- Connect your second HDMI source device to HDMI Input 2.
- Connect the HDMI Output to your TV, monitor, or projector.
- Connect your audio device if needed:
- Use Optical output for a soundbar, AVR, or amplifier.
- Use 3.5mm stereo output for headphones, powered speakers, etc.
- Connect the included power adapter to the BK-21AC.
- Turn on your TV/display, source devices, and audio device.
- Use the front-panel Select button or included remote to switch between Input 1 and Input 2.
- Use the Auto button on the remote to enable or disable automatic switching if needed.
- If audio extraction does not work, check the source device audio format and make sure it matches the audio output you are using.
HDMI Cable Requirement — Critical
For 8K@60Hz, 4K@120Hz, or 1080p@240Hz, use Ultra High-Speed Certified HDMI 2.1 cables under 15 feet.
Understanding the EDID DIP Switches
The BK-21AC includes EDID DIP switches that allow you to manually choose the video and audio capability reported to the source device.
0 = UP | 1 = DOWN
| Switch Position | EDID Description |
| 0000 | Copy EDID from HDMI Output |
| 1000 | 8Kx4K@60 4:2:0/8Kx4K@30 4:4:4/4Kx2K@120Hz 4:4:4, 48G, HDR10, 2CH AUDIO |
| 0100 | 8Kx4K@60 4:2:0/8Kx4K@30 4:4:4/4Kx2K@120Hz 4:4:4, 48G, HDR10, DOLBY/DTS 5.1 |
| 1100 | 8Kx4K@60 4:2:0/8Kx4K@30 4:4:4/4Kx2K@120Hz 4:4:4, 48G, HDR10, HD AUDIO |
| 0010 | 4Kx2K@60, 18G, HDR10, 2CH AUDIO |
| 1010 | 4Kx2K@60, 18G, HDR10, DOLBY/DTS 5.1 |
| 0110 | 4Kx2K@60, 18G, HDR10, HD AUDIO |
| 1110 | 4Kx2K@60, 10.2G, HDR10, 2CH AUDIO |
| 0001 | 4Kx2K@60, 10.2G, HDR10, DOLBY/DTS 5.1 |
| 1001 | 4Kx2K@60, 10.2G, HDR10, HD AUDIO |
| 0101 | 1080p, 2CH AUDIO |
| 1101 | 1080p, DOLBY/DTS 5.1 |
| 0011 | 1080p, HD AUDIO |
| 1011 | 1280x720p@60 DVI |
| 0111 | 1920x1080p@60 DVI |
| 1111 | 4Kx2K@30, 10.2G, HDR, 2CH AUDIO |
Use a 2CH audio EDID when using the 3.5mm stereo output.
Use a Dolby/DTS 5.1 EDID when using Optical with a compatible soundbar, AVR, or amplifier.
Use Copy EDID when you want the source to follow the connected display’s reported capabilities.
What Source Devices Is the BK-21AC Compatible With?
The OREI BK-21AC is compatible with HDMI source devices such as:
- PlayStation 5
- Xbox Series X/S
- Apple TV
- Fire TV Stick
- Roku
- Google Chromecast
- Blu-ray players
- Cable boxes
- Satellite boxes
- Gaming PCs
- Laptops with HDMI output
- Media players
For 8K@60Hz, 4K@120Hz, or 1080p@240Hz, the source device, display, HDMI cables, and EDID setting must all support the required HDMI 2.1 bandwidth.
What Audio Devices Is the BK-21AC Compatible With?
The BK-21AC is compatible with audio devices that accept Optical or 3.5mm stereo input.
It can be used with:
- Optical soundbars
- AVRs with Optical input
- Optical amplifiers
- Powered speakers
- Stereo amplifiers
- Headphones
- 3.5mm speaker systems
For 3.5mm audio, set the source device to PCM or Stereo.
For Optical audio, set the source device to Dolby Digital, DTS 5.1 or Bitstream.
What Displays Is the BK-21AC Compatible With?
The BK-21AC is compatible with HDMI displays such as:
- TVs
- Monitors
- Projectors
- Gaming displays
- 8K displays
- 4K@120Hz displays
- 1080p@240Hz displays
The final resolution and refresh rate will depend on the source device, display, HDMI cables, and EDID settings.
Frequently Asked Questions
Q: What is the OREI BK-21AC used for?
A: The BK-21AC is used to connect two HDMI source devices to one TV, monitor, or projector while also extracting audio through Optical or 3.5mm output.
Q: How is BK-21AC different from BK-21?
A: The BK-21AC includes Optical and 3.5mm audio extraction, while the BK-21 is mainly a 2x1 HDMI switch without separate audio outputs.
Q: How is BK-21AC different from BK-21A?
A: The BK-21AC and the BK-21A are basically the same with the addition of CEC on the BK-21AC.
Q: Is the BK-21AC a seamless switch?
A: No. The BK-21AC is not a seamless switch. When switching inputs, the display will usually go black for a moment while the HDMI signal reconnects.
Q: Why do I see a black screen when switching inputs?
A: This is normal. The display needs time to detect the new HDMI source and complete the HDMI handshake. The delay can vary depending on the TV, source, resolution, refresh rate, and cable quality.
Q: Does auto switching work with Apple TV, Fire TV Stick, Chromecast, or Roku?
A: Auto switching may not work consistently with these devices because they often stay in standby mode and continue sending a 5V HDMI signal. The BK-21AC may still detect them as active even when they appear to be off.
Q: Why does the switch stay on Apple TV even when I turn on my PS5?
A: Apple TV may still be sending a 5V HDMI signal while in standby. Since the BK-21AC still detects Apple TV as active, it may not automatically switch to the PS5. Use the front Select button or remote to switch manually. This applies to other devices like Fire TV Stick, Roku Stick, Chromecast, etc. as well.
Q: How do I turn auto switching on or off?
A: Use the Auto button on the remote to turn automatic switching on or off.
Q: Does CEC work on the BK-21AC?
A: The BK-21AC supports CEC on Input 1 only. CEC behavior can also depend on the connected source, display, HDMI cable, and CEC settings.
Q: Can I display both HDMI sources at the same time?
A: No. The BK-21AC can display only one HDMI source at a time.
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