From 5782246b30bfc11e659cf53b498886a924aa97d1 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Fri, 9 Apr 2021 19:30:38 -0500
Subject: [PATCH] Add hack to prevent video glitching on GFE 3.22 when packets
 per frame exceed 120

---
 src/SdpGenerator.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/SdpGenerator.c b/src/SdpGenerator.c
index 23d9725..ec5a9bd 100644
--- a/src/SdpGenerator.c
+++ b/src/SdpGenerator.c
@@ -150,21 +150,36 @@ static int addGen5Options(PSDP_OPTION* head) {
         // Ask for the encrypted control protocol to ensure remote input will be encrypted.
         // This used to be done via separate RI encryption, but now it is all or nothing.
         err |= addAttributeString(head, "x-nv-general.useReliableUdp", "13");
+
+        if (StreamConfig.bitrate >= 30000 || StreamConfig.width * StreamConfig.height >= 3840 * 2160) {
+            // HACK: GFE 3.22 will split frames into 2 FEC blocks (sharing a frame number)
+            // if the number of packets exceeds ~120. We can't correctly handle those, so
+            // we'll turn off FEC at bitrates above 30 Mbps as an interim hack.
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.repairPercent", "0");
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.numSrcPackets", "511");
+        }
+        else {
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.repairPercent", "20");
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.numSrcPackets", "125");
+        }
     }
     else {
         // We want to use the new ENet connections for control and input
         err |= addAttributeString(head, "x-nv-general.useReliableUdp", "1");
         err |= addAttributeString(head, "x-nv-ri.useControlChannel", "1");
+
+        // When streaming 4K, lower FEC levels to reduce stream overhead
+        if (StreamConfig.width >= 3840 && StreamConfig.height >= 2160) {
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.repairPercent", "5");
+        }
+        else {
+            err |= addAttributeString(head, "x-nv-vqos[0].fec.repairPercent", "20");
+        }
     }
     
     // Disable dynamic resolution switching
     err |= addAttributeString(head, "x-nv-vqos[0].drc.enable", "0");
 
-    // When streaming 4K, lower FEC levels to reduce stream overhead
-    if (StreamConfig.width >= 3840 && StreamConfig.height >= 2160) {
-        err |= addAttributeString(head, "x-nv-vqos[0].fec.repairPercent", "5");
-    }
-
     // Recovery mode can cause the FEC percentage to change mid-frame, which
     // breaks many assumptions in RTP FEC queue.
     err |= addAttributeString(head, "x-nv-general.enableRecoveryMode", "0");