Yes, WebM works for this: you can make SRT and VTT subtitles from WebM files even if the video has no captions inside. Send the WebM to Potok in Telegram and download 2 subtitle files made from its soundtrack. Then load them in your player and confirm the first line appears at the right moment.
Turn a recording into text
Send your voice message, audio or video to @potok_now_bot on Telegram and the text comes back in the chat.
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Export to TXT, MD, DOCX, PDF, SRT and VTT · files up to 2 GB · about 30 languages · speakers and timestamps on request
In short
- The WebM container is a subset of Matroska with the .webm extension; audio-only files should use audio/webm.
- WebM is an open, royalty-free media file format designed for the web.
- The WebM container guidelines store WebVTT as its own track, so a WebM file can carry a WebVTT track.
- The bot reads .webm files of up to 2 GB directly; Potok adds no conversion step.
What a WebM file is
| Property | Value |
|---|---|
| Kind | Open container for the web (a Matroska subset) |
| Media types | video/webm, audio/webm |
| What it holds | A subset of Matroska with the .webm extension; VP8 or VP9 video, Vorbis or Opus audio |
How to make subtitles from WebM files
- Upload the .webm file. Start a chat with @potok_now_bot and upload the WebM file. Each file may be up to 2 GB, and the Upload button in the mini app handles the largest ones.
- One property of the format matters. The WebM container guidelines store WebVTT as its own track, so a WebM file can carry a WebVTT track.
- Get the subtitle file. Press the SRT or VTT export button; each caption carries a start and an end time. Then attach the file to the video and check how it lines up.
- A useful detail. WebM is an open, royalty-free media file format designed for the web.
What the subtitle file looks like
[00:00:01,000 --> 00:00:03,400] Caption 1: Welcome back to the show about home cooking.
[00:00:03,600 --> 00:00:06,100] Caption 2: This week we talk about slow-cooked soups.
[00:00:06,300 --> 00:00:09,000] Caption 3: My guest has run a market stall for decades.
[00:00:09,200 --> 00:00:11,800] Caption 4: Today's lecture covers how rivers shape the land over time.
Captions written by us to show the layout. They are not output from a real WebM file.
| Option | What it means |
|---|---|
| Where it works | In Telegram, through @potok_now_bot; the bot's mini app takes large files |
| Export | TXT, MD, DOCX, PDF, SRT, VTT |
| Upload limit | Files up to 2 GB |
| Digest | Press the summary button under a finished transcript for a short digest |
| Translation | The transcript is not translated into another language |
Typical WebM slips
| Mistake | What happens | Fix |
|---|---|---|
| Assuming a WebM always has a built-in WebVTT track | The video plays without captions because none were added | Load the VTT file separately or mux it into the video |
| Giving a WebM subtitle file the wrong extension | The player ignores the file and shows no captions | Use .vtt for web players and .srt for desktop editors |
| Sending a WebM whose audio track is muted | The bot has no speech to transcribe and returns nothing | Check that the WebM has Opus or Vorbis sound first |
| Expecting the VTT to carry styling from the video | Colors and positions are lost; only plain timed text remains | Set caption styling in the player after loading the file |
More
Terms used here are explained in the glossary. Handy helpers live in tools; apps are on the download page.
Frequently asked questions
Is WebM supported?
It is: the bot takes .webm files of up to 2 GB and decodes them itself, so you do not need to convert anything first.
Will the captions be burned into my WebM file?
No. You get a separate .srt or .vtt text file, and your original WebM file stays unchanged.
Which apps and devices create WebM files?
Android MediaRecorder offers a WEBM output format (Android MediaRecorder WEBM).
Sources
The dates show when each source was opened. Pages are edited over time; read the original before you rely on a detail.
- About WebM, The WebM Project · checked
- WebM container guidelines, The WebM Project · checked
Run your own recording through it
Drop an audio or video file, or a voice message, into the chat with @potok_now_bot; the recognized text is sent back there.
Open @potok_now_bot in Telegram