Subtitles

Subtitles in the formats players meet: SRT, ASS, WebVTT and MP4 text, in the file and as sidecar files.

The files

6 files in snapshot 2026-11-02. Each one's full fact sheet and recipe: GET /v1/cases/{id}, no token needed.

• ASS subtitles in Matroskasubs/ass.mkv Matroska1920x1080 H.264 at 30 fps, stereo AAC at 48 kHz, 6 s, 5.5 MB Facts
• mov_text subtitles in MP4subs/mov-text.mp4 MP41920x1080 H.264 at 30 fps, stereo AAC at 48 kHz, 6 s, 5.5 MB Facts
• SRT sidecar filesubs/sidecar.srt SRTSRT subtitles, 1 kB Facts
• WebVTT sidecar filesubs/sidecar.vtt WebVTTWebVTT subtitles, 1 kB Facts
• SRT subtitles in Matroskasubs/srt.mkv Matroska1920x1080 H.264 at 30 fps, stereo AAC at 48 kHz, 6 s, 5.5 MB Facts
• WebVTT subtitles in WebMsubs/webvtt.webm WebM1920x1080 VP9 at 30 fps, stereo Opus at 48 kHz, 6 s, 5.3 MB Facts

What's in every file

Every video carries its frame number and timecode, burned in at the top left, a frame code along the bottom that the checker reads, and a white flash in the first three frames of every second. The audio carries a tone with a 40 ms beep at the start of every second. So a test can tell which frame is on screen, whether any were dropped, and whether sound and picture line up.

How they were verified

Before publishing, every file was probed and decoded by FFmpeg 7.1.5-0+deb13u1 and GStreamer 1.26.2 (sidecar subtitle files are probed only), and every file with video was played through the testsrc checker, which reads the frame code to confirm frames, timing, orientation, aspect and colour.

Use them

# one file's facts
curl https://testsrc.com/v1/cases/subs/ass.mkv

# play every file in this category through your player and check what it showed
testsrc run --player libvlc subs/

See the API reference for tokens, quotas and snapshots.

Other baseline categories