Variable-frame-rate detection: report the actual inspected interval
A frame-rate inspection describes the pictures and timestamps it actually analyzed. A short interval that appears regular is not proof that an entire recording is constant-rate. Retain the source, choose representative intervals and report their scope before using a rate label to diagnose an editor’s behavior.
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Record the source and the timing question
Keep the authorized original and inspect its video stream, nominal rate fields and actual receiving symptom. A file can advertise a familiar average rate while individual presentation intervals vary. Conversely, decoder reordering and coarse displayed time counters do not automatically establish variable presentation cadence.
Choose intervals containing motion and known changes in capture conditions where practical. A static or short opening can conceal behavior later in a screen recording. Record the stream and source version so a retimed derivative is not accidentally used as evidence about the parent. Detection after a cadence-changing filter measures that changed path, not the untouched source.
Run an explicitly bounded native diagnostic
Check the installed vfrdet filter. An illustrative initial inspection is ffmpeg -t 10 -i source.mp4 -map 0:v:0 -vf vfrdet -an -f null -. The input duration is placed before -i to bound the source read. This analyzes selected decoded video and writes no finished media file; retain its actual summary and command result with the source identity.
Inspect another known source position using a deliberate input seek and bounded interval, for example ffmpeg -ss 60 -t 10 -i source.mp4 -map 0:v:0 -vf vfrdet -an -f null -. Seeking and available source boundaries can affect what was actually decoded, so record the observed interval and do not imply exact whole-file coverage. Avoid adding fps or another retiming filter before this diagnostic when your question concerns original timing.
Interpret the evidence and verify the editor separately
Compare the interval results and relevant presentation timestamps with the receiving problem. A varying-duration report identifies timing behavior within the inspection scope; it does not prove why every editor drifts or that frames are damaged. A regular short result likewise cannot rule out variation elsewhere or establish that independently recorded audio uses a matching clock.
If a constant-cadence derivative is appropriate, choose a supported conversion and verify picture, sound and duration through the separate frame-rate guide. Keep the unchanged parent and distinguish duplicated or dropped pictures from newly captured detail. Do not re-encode an entire archive merely to make a rate label look regular. SocialVidDownloader does not certify whole-source cadence from one sample or automatically repair every editor timeline. Record the bounded diagnostic and the actual receiving test as different outcomes, with unresolved intervals still explicit.
Worked example
Example: the first ten seconds of a screen recording look regular, while a later capture segment varies. The reviewer records both intervals and tests an appropriate derivative in the editor. The initial summary is never presented as proof that the entire parent was constant-rate.
Related guidance
Sources and verification
Reviewed 2026-10-13. Product behavior is limited to available source formats and provider access; it is not a promise that every public link works.