From b5c21205d80953b11812135c15c20bbee0cf0373 Mon Sep 17 00:00:00 2001
From: Ben Kucera <14625260+Bkucera@users.noreply.github.com>
Date: Fri, 7 Feb 2020 17:16:00 -0500
Subject: [PATCH] =?UTF-8?q?fix(ff):=20use=20fixed=20inputFPS=20instead=20o?=
 =?UTF-8?q?f=20vfr=20to=20prevent=20dropped=20f=E2=80=A6=20(#6368)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* fix(ff): use fixed inputFPS instead of vfr to prevent dropped frames
---
 packages/server/lib/video_capture.js | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/packages/server/lib/video_capture.js b/packages/server/lib/video_capture.js
index 560161b7b9b8..38f4cb90607f 100644
--- a/packages/server/lib/video_capture.js
+++ b/packages/server/lib/video_capture.js
@@ -167,10 +167,19 @@ module.exports = {
         if (options.webmInput) {
           cmd
           .inputFormat('webm')
-          .outputOption('-vsync vfr')
+
+          // assume 18 fps. This number comes from manual measurement of avg fps coming from firefox.
+          // TODO: replace this with the 'vfr' option below when dropped frames issue is fixed.
+          .inputFPS(18)
+
+          // 'vsync vfr' (variable framerate) works perfectly but fails on top page navigation
+          // since video timestamp resets to 0, timestamps already written will be dropped
+          // .outputOption('-vsync vfr')
+
           // this is to prevent the error "invalid data input" error
           // when input frames have an odd resolution
           .videoFilters(`crop='floor(in_w/2)*2:floor(in_h/2)*2'`)
+
           // same as above but scales instead of crops
           // .videoFilters("scale=trunc(iw/2)*2:trunc(ih/2)*2")
         } else {