RealSub

RealSub FAQ

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App 1.0.1 / last updated 2026-10-04. Free tiers, model names and endpoints of third-party services are the vendors’ to change; their own documentation is authoritative.

Q1. Does translation work from mainland China?

Q2. Why are no subtitles appearing?

Check these in order of likelihood:

  1. What is playing is singing, pure music, or a voice with radio/walkie-talkie processing. Those do not produce subtitles at the moment.
  2. The wrong audio source is selected. If you picked a specific app under Settings → Transcription → Audio source, only that app is transcribed. Switch back to “Entire system (default)” to capture everything.
  3. The app you want is not in the list. Windows only creates an audio session for an app once it has actually made a sound — play something first, then refresh the list. Per-app capture also requires Windows 10 version 2004 or newer.
  4. System volume is at zero, the app is muted, or the volume is very low. There is no audio to capture while muted. Very quiet audio is boosted automatically (up to 20x) and a one-time notice appears; for the best recognition quality, raise the Windows volume or the playback app’s volume. You can also open the output device’s additional properties in Windows sound settings (Windows 11: “More sound settings” → the device → Properties) and enable “Loudness Equalization” on the Enhancements tab to even out the output level.
  5. Transcription is not running. Check whether the tray menu shows Start or Stop, or toggle it with Ctrl+Alt+S.
  6. The subtitle window is hidden or off-screen. Toggle it with Ctrl+Alt+H, or use “Reset window position” under Settings → Hotkeys & More → Window (the tray menu has the same entry).
  7. Only the translated line is missing. The free version does not include translation; the recognized text still appears normally. Translation is unlocked by the Full Version DLC.

If none of that helps, use “Export diagnostics…” in the tray menu and send the resulting zip with a short description to our support address.

Q3. Should I buy the Full Version DLC?

Use the free version first, then decide. That is a real recommendation, not a formality:

If you have already decided to refund, that is completely fine. We would just ask you to spend a few minutes with the free version first — several common surprises (no subtitles for singing, some GPUs may not get acceleration) are stated openly in the “what it does not do” section on the store page.

Q4. What GPU do I need? What if I don’t have an NVIDIA GPU?

Q5. Does it need the internet? Is my audio uploaded?

Q6. Which languages are supported?

Q7. What happens when the 7-day trial ends?

The app switches to the free version automatically:

Q8. Can I use the exported subtitles directly on a video?

Yes — you can export SRT subtitles or plain TXT (Full Version required). Note that:

Q9. Why does the translation always lag behind the original text?

With the default local translation, translations appear almost together with the original. The rest of this answer applies when an online translation service such as Microsoft Translator is in use.

That is how sentence-level translation works — it is not a network fault. The original text streams in while the speaker is still talking; the translation is only requested once a sentence boundary is found, and the result takes another second or two to come back.

The original (white/grey) line stays real-time and is not affected. Only if translations stop appearing entirely or go missing frequently is the translation service itself likely unreachable — try a different source under Settings → Translation.

Q10. The subtitles disappear as soon as the player goes fullscreen?

Once a second the subtitle window checks whether another window is covering it, and only then re-asserts its always-on-top status. With ordinary fullscreen playback (PotPlayer, VLC, mpv, browser fullscreen, apps like Netflix) it comes back on top within a second.

If it still does not show, the player is most likely using exclusive fullscreen (PotPlayer’s “Direct3D exclusive mode”, madVR’s fullscreen exclusive mode, mpv’s --d3d11-exclusive-fs, etc.). In exclusive fullscreen nothing can be drawn over the video — not even Windows’ own volume pop-up. If you change the volume and see no system volume bar, that is the case. Turn off exclusive mode in the player’s settings, or use borderless windowed fullscreen instead.

There is one more case, and it only happens on Windows 10: if a Store app such as the built-in Movies & TV is already fullscreen the moment it starts, Windows puts that fullscreen view on a higher display layer than ordinary always-on-top windows, and the subtitle window cannot reach it. Leave fullscreen and enter it once more — from then on the subtitles stay on top.

Q11. How do I fill in “Local / LAN server”?

This option is for people who already run an OpenAI-compatible translation server on their own PC or LAN. No account or key is involved. Only local and LAN addresses are accepted (localhost, 127.x, 10.x, 192.168.x, 172.16-31.x); public internet addresses are rejected.

Server API URL (up to /v1) Model name Notes
Ollama http://127.0.0.1:11434/v1 a model you have pulled, e.g. qwen2.5:7b required; a wrong name returns “model not found”
LM Studio http://127.0.0.1:1234/v1 the identifier shown in LM Studio, or leave empty empty = the currently loaded model; start the local server in LM Studio first
llama-server (llama.cpp) http://127.0.0.1:8080/v1 anything, or empty serves one model; the name is ignored
another machine on your LAN http://192.168.1.20:11434/v1 as above replace 127.0.0.1 with that machine’s LAN IP and make sure the server listens on 0.0.0.0

To verify: after entering the address and model name, play a video with speech; the translated line appearing means it works. If the server is unreachable or the model name is wrong, the subtitle bar reports a translation-source failure and falls back to Microsoft Translator automatically. Quality depends on the model you pick; general 7B+ models are usually usable for Japanese → Chinese, smaller ones are noticeably stiff.

Q12. It sits on “Loading…” for a long time after launch. Is it frozen?

No. To keep transcription fully offline, RealSub ships the speech model and the GPU runtime libraries locally, and every cold start (the first launch after booting) reads about 4 GB from disk:

While loading, the subtitle bar shows the current stage and the seconds waited; as long as the number keeps ticking, everything is fine. Launching again in the same Windows session is much faster because the files are already cached in memory.

To speed it up, keep your Steam library on an internal SSD. Steam’s “Settings → Storage” can move installed content without downloading it again.

Q13. After updating, the first launch was slow / it re-tested my GPU / why is my GPU not being used?

Updating to 1.0.1 changes three things:

  1. The first launch re-runs the GPU performance test, once. The test changed in this version, so the result saved by the old version no longer applies, and that one launch takes roughly ten seconds to under a minute longer. Later launches are back to normal. The new test is also stricter: weaker AMD / Intel graphics and integrated GPUs that only just passed before may now be placed in CPU mode, with a “Switched to CPU mode” notification and the device setting changed to “CPU”. That is intended, not a fault — on those PCs the CPU engine keeps up better than the GPU did (see Q4). NVIDIA GPUs are not affected.
  2. GPUs that an older version stopped using after a single error get another chance automatically. Older versions could give up on a GPU for good after one error at runtime; those records no longer apply. (From 1.0.1 on, errors at runtime only switch to CPU for the current session; restarting RealSub goes back to the GPU.)
  3. A device setting of “CPU” is not changed back for you. If an older version switched your device to “CPU” (you would have seen a “Switched to CPU mode” notification at the time), the update leaves it alone — it is part of your settings. To give your GPU another chance, open Settings → Transcription and set Device back to “Auto”. If the GPU passes the test it is used; if not, RealSub simply returns to CPU mode and tells you.