[Bug] TED.com extractor downloads corrupted/desynchronized subtitles #15059
Description
Checklist
- I'm reporting that yt-dlp is broken on a supported site
- I've verified that I have updated yt-dlp to nightly or master (update instructions)
- I've checked that all provided URLs are playable in a browser with the same IP and same login details
- I've checked that all URLs and arguments with special characters are properly quoted or escaped
- I've searched known issues, the FAQ, and the bugtracker for similar issues including closed ones. DO NOT post duplicates
- I've read the policy against AI/LLM contributions and understand I may be blocked from the repository if it is violated
- I've read about sharing account credentials and I'm willing to share it if required
Region
United States
Provide a description that is worded well enough to be understood
When downloading subtitles from TED.com, yt-dlp downloads a corrupted and desynchronized VTT file.
If I download the subtitle file manually from the browser's Network tab (F12 -> filter by "vtt"), I get a different, perfectly synchronized VTT file. This suggests the yt-dlp extractor is grabbing the wrong subtitle source (perhaps a raw/automatic transcript instead of the final "curated" VTT file used by the web player).
Example URL:
https://www.ted.com/talks/sasha_luccioni_we_re_doing_ai_all_wrong_here_s_how_to_get_it_right
Command Used:
yt-dlp -vU --write-subs --sub-lang en --skip-download https://www.ted.com/talks/sasha_luccioni_we_re_doing_ai_all_wrong_here_s_how_to_get_it_right
Evidence: VTT File Comparison
Here is the content of the two different VTT files for comparison.
1. Corrupted Subtitle (Downloaded by yt-dlp)
[subtitle downloaded by ytdlp.txt](https://github.com/user-attachments/files/23551097/subtitle.downloaded.by.ytdlp.txt)
- Correct Subtitle (Downloaded manually from Browser Network Tab)
subtitle downloaded manuallyi by me.txt
Provide verbose output that clearly demonstrates the problem
- Run your yt-dlp command with -vU flag added (
yt-dlp -vU <your command line>) - If using API, add
'verbose': TruetoYoutubeDLparams instead - Copy the WHOLE output (starting with
[debug] Command-line config) and insert it below
Complete Verbose Output
[debug] Command-line config: ['-vU', '--write-subs', '--sub-lang', 'en', '--skip-download', 'https://www.ted.com/talks/sasha_luccioni_we_re_doing_ai_all_wrong_here_s_how_to_get_it_right']
[debug] Encodings: locale cp1252, fs utf-8, pref cp1252, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version stable@2025.11.12 from yt-dlp/yt-dlp [335653be8] (win_exe)
[debug] Python 3.10.11 (CPython AMD64 64bit) - Windows-10-10.0.26200-SP0 (OpenSSL 1.1.1t 7 Feb 2023)
[debug] exe versions: ffmpeg 7.1.1-full_build-www.gyan.dev (setts), ffprobe 7.1.1-full_build-www.gyan.dev
[debug] Optional libraries: Cryptodome-3.23.0, brotli-1.2.0, certifi-2025.10.05, curl_cffi-0.13.0, mutagen-1.47.0, requests-2.32.5, sqlite3-3.40.1, urllib3-2.5.0, websockets-15.0.1, yt_dlp_ejs-0.3.1
[debug] JS runtimes: none
[debug] Proxy map: {}
[debug] Request Handlers: urllib, requests, websockets, curl_cffi
[debug] Plugin directories: none
[debug] Loaded 1844 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest
Latest version: stable@2025.11.12 from yt-dlp/yt-dlp
yt-dlp is up to date (stable@2025.11.12 from yt-dlp/yt-dlp)
[TedTalk] Extracting URL: https://www.ted.com/talks/sasha_luccioni_we_re_doing_ai_all_wrong_here_s_how_to_get_it_right
[TedTalk] sasha_luccioni_we_re_doing_ai_all_wrong_here_s_how_to_get_it_right: Downloading webpage
[TedTalk] 163123: Downloading m3u8 information
[info] 163123: Downloading subtitles: en
[debug] Formats sorted by: hasvid, ie_pref, lang, quality, res, fps, hdr:12(7), vcodec, channels, acodec, size, br, asr, proto, vext, aext, hasaud, source, id
[debug] Default format spec: bestvideo*+bestaudio/best
[info] 163123: Downloading 1 format(s): hls-3122+hls-audio0-medium
[info] Writing video subtitles to: We’re doing AI all wrong. Here’s how to get it right [163123].en.vtt
[debug] Invoking hlsnative downloader on "https://hls.ted.com/project_masters/11036/subtitles/en.m3u8?intro_master_id=8647"
[hlsnative] Downloading m3u8 manifest
[hlsnative] Total fragments: 22
[download] Destination: We’re doing AI all wrong. Here’s how to get it right [163123].en.vtt
[debug] File locking is not supported. Proceeding without locking
[download] 100% of 17.21KiB in 00:00:02 at 7.11KiB/s
PS C:\MYSOFT\ytdlp>