From 3de2fd9b5378a9c472433baa7556c8fef61a482e Mon Sep 17 00:00:00 2001
From: Timothy Pearson <tpearson@raptorengineering.com>
Date: Mon, 9 Dec 2019 00:36:54 -0600
Subject: Re-read actual capture timebase from V4L2 after framerate request

Sometimes V4L2 drivers can change the actual capture timebase after
a framerate request is made.  Ensure the actual capture timebase is
read / reported instead of what ffmpeg tried to use.
---
 libavdevice/v4l2.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
index 365bacd..15e1258 100644
--- a/libavdevice/v4l2.c
+++ b/libavdevice/v4l2.c
@@ -740,6 +740,13 @@ static int v4l2_set_parameters(AVFormatContext *ctx)
                 return ret;
             }
 
+            if (v4l2_ioctl(s->fd, VIDIOC_G_PARM, &streamparm) < 0) {
+                ret = AVERROR(errno);
+                av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_PARM): %s\n",
+                av_err2str(ret));
+                return ret;
+            }
+
             if (framerate_q.num != tpf->denominator ||
                 framerate_q.den != tpf->numerator) {
                 av_log(ctx, AV_LOG_INFO,
-- 
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