command, demux: add AB-loop keyframe cache align command

Helper for the ab-loop-dump-cache command, see manpage additions.

This is kind of shit. Not only is this a very "special" feature, but it
also vomits more messy code into the big and already bloated demux.c,
and the implementation is sort of duplicated with the dump-cache code.
(Except it's different.) In addition, the results sort of depend what a
video player would do with the dump-cache output, or what the user wants
(for example, a user might be more interested in the range of output
audio, instead of the video).

But hey, I don't actually need to justify it. I'm only justifying it for
fun.

1 files changed, 9 insertions, 0 deletions

diff --git a/DOCS/man/input.rst b/DOCS/man/input.rst
index fdbe4e5fd8..393ac9b9ee 100644
--- a/DOCS/man/input.rst
+++ b/DOCS/man/input.rst
@@ -974,6 +974,15 @@ Input Commands that are Possibly Subject to Change
     The author reserves the right to remove this command if enough motivation
     is found to move this functionality to a trivial Lua script.
 
+``ab-loop-align-cache``
+    Re-adjust the A/B loop points to the start and end within the cache the
+    ``ab-loop-dump-cache`` command will (probably) dump. Basically, it aligns
+    the times on keyframes. The guess might be off especially at the end (due to
+    granularity issues due to remuxing). If the cache shrinks in the meantime,
+    the points set by the command will not be the effective parameters either.
+
+    This command has an even more uncertain future than ``ab-loop-dump-cache``
+    and might disappear without replacement if the author decides it's useless.
 
 Undocumented commands: ``ao-reload`` (experimental/internal).