LADSPA latency compensation
|Reported by:||Laurence Tratt||Owned by:|
|Blocking:||Reproduced by developer:||no|
|Analyzed by developer:||no|
A common idiom for LADSPA plugins is for them to report their latency with a "latency" output control port which the invoking program can use to correct the output. For example, sox has "ladspa -l" (see https://sourceforge.net/p/sox/patches/101/) and Audacity defaults to using this idiom (https://manual.audacityteam.org/man/effect_menu_ladspa.html). ffmpeg doesn't seem to do this automatically (which is fair enough, as it's not a guaranteed standard), but doesn't seem to have any way to do it optionally, nor any way?
For example, consider the noise-gate plugin https://github.com/feuerbach/noise-gate. If it's used as such:
ffmpeg -i in.aac -af "ladspa=file=/usr/local/lib/ladspa/ng.so:p=noise_gate:c=c0=-35|c1=1500|c2=150|c3=50" -c:a aac -y out.aac
then 'out.aac' will be both substantially delayed relative to 'in.aac' as well as having the input cut off. You can see the noise-gate plugin defining the output port here for example:
I think https://trac.ffmpeg.org/ticket/7616 is related to this issue, although the report there isn't clear about how common this idiom is.
Change History (5)
comment:4 by , 15 months ago
|Component:||undetermined → avfilter|
|Priority:||normal → wish|
|Resolution:||invalid → fixed|
|Version:||unspecified → git-master|