No delay
The track is translated in batches ahead of the video, so each line is ready before it is spoken.
Translated YouTube subtitles, in time with the speech
When a video already has subtitles, SubLive does not need to listen to it. It takes the subtitle track, translates it ahead of playback and shows each line at the moment it is spoken. Pause, rewind or watch at double speed, and the translation stays in step.
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Translating the sound versus translating the track
What is said
So here is the plan.First we test it.Then we ship it.
Translated from the sound
So here is the plan.First we test it.Then we ship it.
Translated from the subtitle track
So here is the plan.First we test it.Then we ship it.
- From the sound, a line can be translated only after it has been said, so it arrives about a sentence late.
- From the track, every line is translated before it plays and appears together with the speech.
Por qué importa
Whole sentences
Auto-generated YouTube captions arrive word by word. SubLive joins them into sentences and translates each one with the lines around it.
Ready before it is said
SubLive translates about ninety seconds of the track ahead of playback and asks for the next stretch thirty seconds before that runs out, so the video never waits for the translator.
Cómo funciona
- 1
Open a video with subtitles
On YouTube, or on a site whose HTML5 player has a subtitle track, such as TED. Start SubLive the usual way.
- 2
SubLive picks the track
Human-made subtitles come before auto-generated ones. If a human track in your language already exists, it is shown as it is, with no machine translation.
- 3
Or let it listen
One switch in the extension makes SubLive listen to the sound instead. Videos without subtitles, live streams and calls always work that way.
How many seconds the subtitle track saves
When SubLive translates from the sound, the clock starts only once a phrase has been said. It waits 0.7 seconds of silence to be sure the phrase is over, translates it in about three quarters of a second and puts it on screen. The AI voice needs roughly another second before its first sound.
From the subtitle track, all of that happens ahead of time. The line is already translated when the speaker starts the phrase, so it appears together with it: zero seconds after the phrase begins, not 1.6 seconds after it ends. Only the very start of a video waits once, while the first stretch of the track is translated.
Seconds from the end of a phrase until you see or hear it
Each step in seconds, on one scale: the full circle is three seconds.
Subtitle, translated from the sound
- Waiting for the pause 0.7 s
- Translation 0.75 s
- Putting the line on screen 0.12 s
AI voice, translated from the sound
- Waiting for the pause 0.7 s
- Translation 0.75 s
- AI voice, first sound 1.1 s
Subtitle or voice from the subtitle track
Translation is the average over 386 phrases on SubLive servers on 20 October 2026. The pause and the display step are fixed settings, and the first sound of the AI voice is our own measurement. Recognition can add a little on top, while translation sometimes starts before the pause is over, so the totals are approximate.
Fuentes: SubLive production metrics, 20 October 2026; speech recognition setting: 700 ms of silence ends a phrase; SubLive latency review: about 1.1 s to the first sound of the AI voice
Does it work with auto-generated YouTube captions?
Yes, in every language YouTube generates them for. Automatic captions come in short fragments, a word or two at a time, so SubLive first puts the words back into sentences and only then translates them. Whenever a video also has human-made subtitles, those are used first.
Hearing the translation of a video
The AI voice can read the translated subtitles aloud. Each line starts together with the speech it replaces, and the video's own sound gets quieter underneath.
Lo que no hará
- Live streams and YouTube Shorts are translated from the sound, as before.
- A YouTube video embedded on another website is translated from the sound too.
- Many web players keep their subtitles to themselves. On those sites SubLive listens instead.
- No transcript is saved in this mode.
Preguntas frecuentes
- What if the video has no subtitles?
- Then SubLive listens to the sound, the same way it does on a call, and the subtitles run about a sentence behind the speaker.
- Can I keep the original sound and read the translation?
- Yes. That is the default: the video plays as it is, and the translated lines appear in the subtitle window. The voice is off until you pick one.
- Does skipping ahead break it?
- No. The translation follows the video's own clock, so seeking, pausing and changing speed keep every line in its place.