From 1dd9036da60c4ef578b6fb928ae7231bc2a82361 Mon Sep 17 00:00:00 2001
From: mjbudd77 <mjbudd77@gmail.com>
Date: Thu, 16 Sep 2021 23:40:29 -0400
Subject: [PATCH] Bug fix for libav MPEG4 video frame rate encoding.

---
 src/drivers/Qt/AviRecord.cpp | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/drivers/Qt/AviRecord.cpp b/src/drivers/Qt/AviRecord.cpp
index 9a661862..cbb9c961 100644
--- a/src/drivers/Qt/AviRecord.cpp
+++ b/src/drivers/Qt/AviRecord.cpp
@@ -821,9 +821,12 @@ static int initVideoStream( enum AVCodecID codec_id, OutputStream *ost )
 	AVCodecContext *c;
 	double fps;
 	int fps1000;
+	unsigned int usec;
 
 	fps = getBaseFrameRate();
 
+	usec = (unsigned int)((1.0e6 / fps)+0.50);
+
 	fps1000 = (int)(fps * 1000.0);
 
 	/* find the video encoder */
@@ -866,8 +869,16 @@ static int initVideoStream( enum AVCodecID codec_id, OutputStream *ost )
 	 * timebase should be 1/framerate and timestamp increments should be
 	 * identical to 1. */
 	//ost->st->time_base = (AVRational){ 1000, fps1000 };
-	ost->st->time_base.num = 1000;
-	ost->st->time_base.den = fps1000;
+	if ( codec_id == AV_CODEC_ID_MPEG4 )
+	{   // MPEG4 max num/den is 65535 each
+		ost->st->time_base.num = 1000;
+		ost->st->time_base.den = fps1000;
+	}
+	else
+	{
+		ost->st->time_base.num =    usec;
+		ost->st->time_base.den = 1000000u;
+	}
 	c->time_base       = ost->st->time_base;
 	c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
 	c->pix_fmt       = AV_PIX_FMT_YUV420P;