From 67068e4e3d7ab17de425651848eecea530ac8b88 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Fri, 11 Feb 2022 19:33:35 +0100
Subject: [PATCH] Pass key frame flag from the device

MediaCodec indicates when a packet is a key frame. Transmit it to the
client.
---
 app/src/demuxer.c                                | 16 +++++++++++-----
 .../com/genymobile/scrcpy/ScreenEncoder.java     |  4 ++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/app/src/demuxer.c b/app/src/demuxer.c
index c2f4a636..417abd27 100644
--- a/app/src/demuxer.c
+++ b/app/src/demuxer.c
@@ -15,8 +15,9 @@
 #define HEADER_SIZE 12
 
 #define SC_PACKET_FLAG_CONFIG    (UINT64_C(1) << 63)
+#define SC_PACKET_FLAG_KEY_FRAME (UINT64_C(1) << 62)
 
-#define SC_PACKET_PTS_MASK (SC_PACKET_FLAG_CONFIG - 1)
+#define SC_PACKET_PTS_MASK (SC_PACKET_FLAG_KEY_FRAME - 1)
 
 static bool
 sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
@@ -35,10 +36,11 @@ sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
     // The most significant bits of the PTS are used for packet flags:
     //
     //  byte 7   byte 6   byte 5   byte 4   byte 3   byte 2   byte 1   byte 0
-    // C....... ........ ........ ........ ........ ........ ........ ........
-    // ^<-------------------------------------------------------------------->
-    // |                                 PTS
-    //  `- config packet
+    // CK...... ........ ........ ........ ........ ........ ........ ........
+    // ^^<------------------------------------------------------------------->
+    // ||                                PTS
+    // | `- config packet
+    //  `-- key frame
 
     uint8_t header[HEADER_SIZE];
     ssize_t r = net_recv_all(demuxer->socket, header, HEADER_SIZE);
@@ -67,6 +69,10 @@ sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
         packet->pts = pts_flags & SC_PACKET_PTS_MASK;
     }
 
+    if (pts_flags & SC_PACKET_FLAG_KEY_FRAME) {
+        packet->flags |= AV_PKT_FLAG_KEY;
+    }
+
     return true;
 }
 
diff --git a/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java b/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java
index a51a8a32..f97206ec 100644
--- a/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java
+++ b/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java
@@ -29,6 +29,7 @@ public class ScreenEncoder implements Device.RotationListener {
     private static final int[] MAX_SIZE_FALLBACK = {2560, 1920, 1600, 1280, 1024, 800};
 
     private static final long PACKET_FLAG_CONFIG = 1L << 63;
+    private static final long PACKET_FLAG_KEY_FRAME = 1L << 62;
 
     private final AtomicBoolean rotationChanged = new AtomicBoolean();
     private final ByteBuffer headerBuffer = ByteBuffer.allocate(12);
@@ -189,6 +190,9 @@ public class ScreenEncoder implements Device.RotationListener {
                 ptsOrigin = bufferInfo.presentationTimeUs;
             }
             pts = bufferInfo.presentationTimeUs - ptsOrigin;
+            if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_KEY_FRAME) != 0) {
+                pts |= PACKET_FLAG_KEY_FRAME;
+            }
         }
 
         headerBuffer.putLong(pts);