From 39feabe35c5175a2c497b3b4ac79787c1bc14ab1 Mon Sep 17 00:00:00 2001
From: Benjamin Wright <benwright@webrtc.org>
Date: Mon, 22 Oct 2018 13:33:09 -0700
Subject: [PATCH] Enables FrameDecryptor to do an initial key request on frame
 decryption.
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This change enables the FrameDecryptor attached to an RtpVideoReceiver to do
an initial request for a KeyFrame if the first successfully decrypted payload
is not a key frame.

Bug: webrtc:9795
Change-Id: I401ce1f513cb51ce520b60dcaf8b825a68d00c7f
Reviewed-on: https://webrtc-review.googlesource.com/c/107246
Commit-Queue: Benjamin Wright <benwright@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25295}
---
 video/rtp_video_stream_receiver.cc | 24 ++++++++++++++++++------
 video/rtp_video_stream_receiver.h  |  2 ++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/video/rtp_video_stream_receiver.cc b/video/rtp_video_stream_receiver.cc
index b3cf7fbbf2..6f1724f41a 100644
--- a/video/rtp_video_stream_receiver.cc
+++ b/video/rtp_video_stream_receiver.cc
@@ -378,6 +378,16 @@ int32_t RtpVideoStreamReceiver::ResendPackets(const uint16_t* sequence_numbers,
 
 void RtpVideoStreamReceiver::OnReceivedFrame(
     std::unique_ptr<video_coding::RtpFrameObject> frame) {
+  // Request a key frame as soon as possible.
+  bool key_frame_requested = false;
+  if (!has_received_frame_) {
+    has_received_frame_ = true;
+    if (frame->FrameType() != kVideoFrameKey) {
+      key_frame_requested = true;
+      keyframe_request_sender_->RequestKeyFrame();
+    }
+  }
+
   // Optionally attempt to decrypt the raw video frame if it was provided.
   if (frame_decryptor_ != nullptr) {
     // When using encryption we expect the frame to have the generic descriptor.
@@ -408,6 +418,14 @@ void RtpVideoStreamReceiver::OnReceivedFrame(
             inline_decrypted_bitstream, &bytes_written) != 0) {
       return;
     }
+
+    if (!has_received_decrypted_frame_ && !key_frame_requested) {
+      has_received_decrypted_frame_ = true;
+      if (frame->FrameType() != kVideoFrameKey) {
+        keyframe_request_sender_->RequestKeyFrame();
+      }
+    }
+
     RTC_CHECK(bytes_written <= max_plaintext_byte_size);
     // Update the frame to contain just the written bytes.
     frame->SetLength(bytes_written);
@@ -417,12 +435,6 @@ void RtpVideoStreamReceiver::OnReceivedFrame(
     return;
   }
 
-  if (!has_received_frame_) {
-    has_received_frame_ = true;
-    if (frame->FrameType() != kVideoFrameKey)
-      keyframe_request_sender_->RequestKeyFrame();
-  }
-
   reference_finder_->ManageFrame(std::move(frame));
 }
 
diff --git a/video/rtp_video_stream_receiver.h b/video/rtp_video_stream_receiver.h
index 9c88173a13..ed5164769e 100644
--- a/video/rtp_video_stream_receiver.h
+++ b/video/rtp_video_stream_receiver.h
@@ -208,6 +208,8 @@ class RtpVideoStreamReceiver : public RecoveredPacketReceiver,
 
   // E2EE Video Frame Decryptor (Optional)
   rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor_;
+  // Set to true on the first successsfully decrypted frame.
+  bool has_received_decrypted_frame_ = false;
 };
 
 }  // namespace webrtc