From the FFmpeg filters documentation (R1): multi-input filters such as overlay share "framesync" options, settable only by name. eof_action - what to do when the secondary input hits EOF: "repeat" the last frame (default), "endall" end both streams, or "pass" the main input through untouched....

From the FFmpeg filters documentation (R1): multi-input filters such as overlay share "framesync" options, settable only by name. eof_action - what to do when the secondary input hits EOF: "repeat" the last frame (default), "endall" end both streams, or "pass" the main input through untouched. shortest=1 forces output to end when the shortest input ends (default 0). repeatlast=1 (default) extends the last frame of secondary streams until the primary stream ends; 0 disables. ts_sync_mode - "default" takes the secondary frame with the nearest lower-or-equal timestamp to each primary frame; "nearest" takes the absolutely nearest timestamp. Overlay note: frames are taken from each input in timestamp order, so if the inputs start at different timestamps, pass both through setpts=PTS-STARTPTS so they begin at zero. Overlay expressions can use t (seconds) and n (frame number) only when eval=frame (default); with eval=init they evaluate to NAN. Practical recipes (derived): logo or watermark for the whole programme - default repeat/repeatlast keeps the last overlay frame; a lower-third or AI-generated insert that should disappear when it ends - eof_action=pass; stop everything when either source ends (e.g. side-by-side model comparisons) - shortest=1 or eof_action=endall; mismatched frame rates or VFR AI clips - try ts_sync_mode=nearest after normalising start PTS; to show an overlay only in a window use the timeline option enable='between(t,a,b)'. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Documentation reflects current FFmpeg master; option availability depends on version. Not run (no source execution). Limitations: Documentation reflects current git master; option availability (e.g. ts_sync_mode) depends on FFmpeg version - check ffmpeg -h filter=overlay on the installed build. Recipes are derived, not executed here. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://ffmpeg.org/ffmpeg-filters.html",
      "note": "7 framesync: eof_action; overlay filter note; 7 framesync: ts_sync_mode"
    }
  ]
}