[FFmpeg-devel] Fix incomplete implementation of framesync options for overlay filter

[Howard Peacock]

Hi - first time posting, so apologies in advance if this breaks an etiquette rule.

Just a request / suggestion that the 'overlay' filter be updated to implement all​ the framesync options - including ts_sync_mode. Currently - although https://ffmpeg.org/ffmpeg-filters.html#overlay-1 states that 'This filter also supports the framesync options' - attempting to set ts_sync_mode results in an error - for example:

$ ffmpeg -f v4l2 -i /dev/video0 -filter_complex "[0:v][0:]overlay=x=20:y=20:ts_sync_mode=nearest" -f flv - | ffplay -

Error initializing complex filters.
Option not found

Running ffmpeg -h filter=overlay (and looking at latest source code) confirms that the ts_sync_mode framesync option is not currently implemented in the overlay filter.

The reason for asking is that I'm in a programming context with multiple livestreams (with different start times) and multiple overlays where the second overlay needs to use the 'nearest' rather than 'default' sync behaviour to keep everything in sync, and it's not currently possible - I have to dial in delays manually.

I was thinking of posting as a bug because of the mismatch between documentation and implementation but it's probably a feature request in fairness!
Thanks!
h