From e3c2398aa208d9f85e6cd5474e3201b8b5f203f9 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Fri, 11 Feb 2022 19:31:01 +0100
Subject: [PATCH] Store packet flags in PTS most significant bits

A special PTS value was used to encode a config packet.

To prepare for adding more flags, use the most significant bits of the
PTS field to store flags.
---
 app/src/demuxer.c                             | 22 +++++++++++++++----
 .../com/genymobile/scrcpy/ScreenEncoder.java  |  4 ++--
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/app/src/demuxer.c b/app/src/demuxer.c
index bebdb6d6..c2f4a636 100644
--- a/app/src/demuxer.c
+++ b/app/src/demuxer.c
@@ -13,7 +13,10 @@
 #define BUFSIZE 0x10000
 
 #define HEADER_SIZE 12
-#define NO_PTS UINT64_C(-1)
+
+#define SC_PACKET_FLAG_CONFIG    (UINT64_C(1) << 63)
+
+#define SC_PACKET_PTS_MASK (SC_PACKET_FLAG_CONFIG - 1)
 
 static bool
 sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
@@ -28,6 +31,14 @@ sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
     //                    size
     //
     // It is followed by <packet_size> bytes containing the packet/frame.
+    //
+    // 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
 
     uint8_t header[HEADER_SIZE];
     ssize_t r = net_recv_all(demuxer->socket, header, HEADER_SIZE);
@@ -35,9 +46,8 @@ sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
         return false;
     }
 
-    uint64_t pts = buffer_read64be(header);
+    uint64_t pts_flags = buffer_read64be(header);
     uint32_t len = buffer_read32be(&header[8]);
-    assert(pts == NO_PTS || (pts & 0x8000000000000000) == 0);
     assert(len);
 
     if (av_new_packet(packet, len)) {
@@ -51,7 +61,11 @@ sc_demuxer_recv_packet(struct sc_demuxer *demuxer, AVPacket *packet) {
         return false;
     }
 
-    packet->pts = pts != NO_PTS ? (int64_t) pts : AV_NOPTS_VALUE;
+    if (pts_flags & SC_PACKET_FLAG_CONFIG) {
+        packet->pts = AV_NOPTS_VALUE;
+    } else {
+        packet->pts = pts_flags & SC_PACKET_PTS_MASK;
+    }
 
     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 79efc17c..a51a8a32 100644
--- a/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java
+++ b/server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java
@@ -28,7 +28,7 @@ public class ScreenEncoder implements Device.RotationListener {
     // Keep the values in descending order
     private static final int[] MAX_SIZE_FALLBACK = {2560, 1920, 1600, 1280, 1024, 800};
 
-    private static final int NO_PTS = -1;
+    private static final long PACKET_FLAG_CONFIG = 1L << 63;
 
     private final AtomicBoolean rotationChanged = new AtomicBoolean();
     private final ByteBuffer headerBuffer = ByteBuffer.allocate(12);
@@ -183,7 +183,7 @@ public class ScreenEncoder implements Device.RotationListener {
 
         long pts;
         if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
-            pts = NO_PTS; // non-media data packet
+            pts = PACKET_FLAG_CONFIG; // non-media data packet
         } else {
             if (ptsOrigin == 0) {
                 ptsOrigin = bufferInfo.presentationTimeUs;