To add live captions with SyncWords, send your existing broadcast into a SyncWords Service using RTMP PUSH, configure transcription and Embedded 608 captions, then send SyncWords’ RTMP output to YouTube. YouTube Studio must also have Closed Captions enabled and Embedded 608/708 selected as the caption source. Start the SyncWords Service before sending the incoming stream.
How the caption path works
Your encoder or streaming service sends video and audio to SyncWords; SyncWords creates captions from the audio and sends a captioned stream to YouTube. The workflow below follows SyncWords’ official Send Captions to YouTube (RTMP 608) instructions. The guide’s pages show a 2025 copyright notice but no individual publication or revision date.
- Create a new SyncWords Service or open an existing one.
- In Input Media, choose RTMP PUSH. Copy the generated input details into the streaming software or service that currently sends your program, such as OBS, Wirecast, or StreamYard.
- Configure transcription so SyncWords generates captions from the incoming audio.
- If needed, configure real-time translation or audio dubbing. SyncWords’ RTMP output guide says its output supports languages using Latin character sets; Arabic is an example of a language that will not work for this output route. Check the current guide if your language requirements differ.
- In Output, choose RTMP PUSH and add a destination for YouTube. Under Captions & Subtitles, enable Embedded 608.
- In YouTube Studio, open the stream’s Stream settings and copy its Stream URL and Stream key into the SyncWords destination.
- In YouTube Studio, enable Closed captions and set Captions source to Embedded 608/708.
- Start the SyncWords Service, then start or connect your encoder’s incoming stream. SyncWords says the service must be started to accept incoming streams and deliver its output.
The two caption settings must agree: SyncWords warns that if YouTube’s Closed Captions setting is off or Embedded 608/708 is not selected, the stream passed to YouTube will not contain captions.
Check the incoming stream settings
SyncWords’ YouTube RTMP 608 guide specifies the following parameters for the incoming stream. Treat these as the guide’s requirements, not as independently tested recommendations.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problems#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
| Setting | Value specified by SyncWords |
|---|---|
| Audio sample rate | 44.1 kHz |
| Frame rate | 29.97 or 30 fps |
| Video bitrate | At least 3,500 Kbps |
| Keyframe interval | 2 seconds |
| Aspect ratio | 16:9 or 4:3 |
If your encoder offers these controls, match them before the event and confirm that the video and audio reach SyncWords. Don’t change an established production setup blindly; coordinate any required encoding changes with whoever operates the source stream.
Choose caption, translation, and buffer settings
Same-language captions or translated output
For same-language captions, configure transcription in the service and enable Embedded 608 in the RTMP output. If you add translation or dubbing, choose the required languages and confirm they are compatible with SyncWords’ RTMP output. Translation adds a buffering trade-off: more buffer can accommodate translated audio or subtitles, while a shorter buffer favors lower latency.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Buffer recommendations in SyncWords’ RTMP guide
| Use case | Buffer guidance |
|---|---|
| Translated audio | 60 seconds |
| Translated subtitles only | 30 seconds |
| Low-latency, same-language captions | 0–5 seconds |
These are use-case recommendations from SyncWords’ RTMP output documentation, not a single setting for every stream. Pick the option that fits whether translation is involved and how much delay your audience can tolerate.
CC1 and additional caption channels
SyncWords describes 608 captions as traditional closed captions embedded directly in the video signal. You can assign a language to CC1 and, if required, CC2–CC4. SyncWords cautions that not all players can read captions from CC2–CC4, so verify destination compatibility before relying on those channels. If the source already contains CC1 captions you want to retain, the output guide documents a passthrough choice.
Recommended Free Tools
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Sending to more than one destination
SyncWords’ RTMP output guide documents up to four simultaneous RTMP destinations. Each destination can have its own connector type, URL, stream key, and dubbing language; all destinations receive the same encoded stream and caption set. This can suit a workflow that needs multiple endpoints, but it does not create separate encoded streams or caption sets for each destination.
The output guide also lists frame reordering to support caption embedding across different frame rates and a default late-caption timeout of 30 seconds. If captions appear late or fail to embed as expected, review those advanced options against your actual frame-rate and caption timing needs.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Troubleshoot before going live
- YouTube receives video but no captions: Confirm transcription is configured, Embedded 608 is enabled in the SyncWords output, and YouTube Studio has Closed Captions enabled with Captions source set to Embedded 608/708.
- SyncWords does not receive the source stream: Check that the service is started, the source encoder is using the generated SyncWords RTMP input details, and the source is sending a stream.
- YouTube does not receive the output: Recheck the YouTube Stream URL and Stream key in the RTMP PUSH destination, then confirm the service has been started and is receiving input.
- Captions are late: Review the buffer against the use case. SyncWords recommends 0–5 seconds for low-latency same-language captions, 30 seconds for translated subtitles, and 60 seconds for translated audio.
- A secondary caption language is missing in a player: Check whether the player supports CC2–CC4; SyncWords notes that support for those channels is not universal.
- Translation or dubbing does not work: Confirm the output language uses a Latin character set, as required by SyncWords’ RTMP output documentation.
SyncWords’ documentation does not establish a caption-accuracy figure or guarantee a particular end-to-end latency. Monitor the actual program and captions during a rehearsal rather than assuming either value.
Understand usage billing
SyncWords’ published Live usage page says billing depends on how long an Event or Service is connected and how many outputs it generates; captions, subtitles, or audio translations for each language count as separate outputs. Its example counts one hour of English captions, French and Spanish subtitles, and French audio translation as four hours of usage. The page says the default active-service runtime allowance is three times usage, with additional runtime billed at $0.10 per hour. These are terms stated on that help page, not a quote for a particular plan; confirm current terms for your account.
Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Or let it run in the cloud
SyncWords adds captions to an incoming broadcast; it does not remove the need for a source stream. If your goal is instead to keep prerecorded video live on YouTube 24/7, StreamNeo is a separate cloud service: upload videos, add your YouTube stream key, and go live. Nothing has to stay on at home; it streams the uploaded video as made, up to 4K 60fps, at one price per slot, and automatically recovers if YouTube drops the stream. The first day is free with no card. Monthly pricing is $9.99 per month. StreamNeo is for YouTube and uploaded videos, not camera-based live production or caption generation. Learn more at StreamNeo, or start the free first day.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
