Document the imperative 1.9.0 functions.

[nageru-docs] / video.rst

diff --git a/video.rst b/video.rst
index ed565f8d746b6ff82bbf17527e391d39073c56ba..12e32e3fc8dbe8448ae8c88dd667e780335b5cf2 100644 (file)
--- a/video.rst
+++ b/video.rst
@@ -107,6 +107,23 @@ This is particularly useful when dealing with network streams, as FFmpeg does no
 always properly detect if the connection has been lost. See :ref:`menus`
 for a way to expose such functionality to the operator.
 
+.. _subtitle-ingest:
+
+Ingesting subtitles
+-------------------
+
+Video streams can contain separate subtitle tracks. Since Nageru 1.8.1,
+you can read these streams. This is particularly useful when using Nageru
+and Futatabi together (see :ref:`talkback`).
+
+To get the last subtitle given before the current video frame, call
+“signals:get_last_subtitle(n)” from get_chain, where n is the signal number
+of your video signal. It will either contain nil, if there hasn't been
+a subtitle, or else the raw subtitle. Note that if the video frame and
+the subtitle occur on the exact same timestamp, and the video frame
+is muxed before the subtitle packet, the subtitle will not make it in time.
+(Futatabi puts the subtitle slightly ahead of the video frame to avoid this.)
+
 
 Integration with CasparCG
 -------------------------