FFmpeg interlace evidence: confirm field order before conversion
Interlace flags and a detector’s classification are evidence to review, not an instruction to deinterlace every recording. Inspect moving content and the intended field order before selecting a conversion. Merely marking frames progressive does not reconstruct progressive pictures or correct the temporal order of real fields.
Open the relevant downloader · Platform tools and access limits
Retain the source and inspect meaningful movement
Keep the authorized original and identify the selected video stream. Compare moving hands, scrolling text or another clear action in a suitable receiver. A static scene can make field relationships hard to judge. Record source notes, reported field flags and visible evidence separately, especially when an earlier transcode may have baked combing into progressive-looking frames.
Distinguish top-field-first and bottom-field-first source interpretation from a general interlaced label. Wrong temporal interpretation can make movement look uneven even when the stored pictures decode. Do not infer order solely from resolution or a filename. Mixed material and uncertain detector results require a scoped review rather than one forced setting across the archive.
Run a bounded native detector without rewriting media
An illustrative diagnostic is ffmpeg -t 10 -i source.mp4 -map 0:v:0 -vf idet -an -f null -. The input duration bounds the read before -i, and the output is discarded rather than reported as a repaired movie. Inspect the actual single-frame, multi-frame or repeated-field statistics the installed filter reports and retain their scope.
Compare another representative moving interval when the source contains different scene types. A count from one short passage is not proof of a uniform entire-recording structure. FFmpeg’s setfield marks frame interpretation; it does not itself perform deinterlacing or reorder arbitrary source pixels into a correct temporal sequence. Keep metadata relabeling distinct from actual picture transformation.
Choose a justified derivative and verify field motion
For a known top-field-first source and an agreed one-output-frame-per-input-frame derivative, a bounded example is ffmpeg -t 10 -i source.mp4 -map 0:v:0 -vf "bwdif=mode=send_frame: parity=tff: deint=all" -an -c:v libx264 review-progressive.mp4. It intentionally selects video only and re-encodes it. This is not the right preset for every source, output temporal requirement or ambiguous field order.
Inspect the actual derivative’s moving edges, direction, duration and beginning and ending. Other output modes can change cadence, so choose and verify the required result rather than calling a flag change a progressive restoration. For complete delivery, explicitly retain required audio and captions and check synchronization. Preserve the parent and unresolved field evidence. SocialVidDownloader does not provide forensic field-order repair or certify every source’s scan structure; this native local diagnostic and conditional conversion remain separate from genuine public-source format selection.
Worked example
Example: a detector suggests top-field-first behavior in a moving passage, but another section is progressive. The reviewer records those scopes and avoids forcing one all-recording conversion. A test that smooths one shot but harms another is rejected instead of declared a repaired master.
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.