From 320c57b7c6bf68d8612a4f135f44b3d29e802113 Mon Sep 17 00:00:00 2001
From: Philipp Hancke <philipp.hancke@googlemail.com>
Date: Mon, 31 May 2021 21:07:45 +0200
Subject: [PATCH] red: remove special-casing of no-redundancy

removes the special-casing of not sending a RED header when there is no redundant payload.
This avoids switching back and forth between the primary and the red payload format (primarily at the start of the connection).

BUG=webrtc:11640

Change-Id: I8e0044bef1ed7c4168d9527645522392db2ed068
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/220932
Reviewed-by: Jesus de Vicente Pena <devicentepena@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34703}
---
 .../codecs/red/audio_encoder_copy_red.cc      | 19 +++++--------------
 .../red/audio_encoder_copy_red_unittest.cc    | 11 +++++++----
 2 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/modules/audio_coding/codecs/red/audio_encoder_copy_red.cc b/modules/audio_coding/codecs/red/audio_encoder_copy_red.cc
index 07dd3caeb7..b88dbbf843 100644
--- a/modules/audio_coding/codecs/red/audio_encoder_copy_red.cc
+++ b/modules/audio_coding/codecs/red/audio_encoder_copy_red.cc
@@ -122,12 +122,7 @@ AudioEncoder::EncodedInfo AudioEncoderCopyRed::EncodeImpl(
     header_length_bytes += kRedHeaderLength;
   }
 
-  // Allocate room for RFC 2198 header if there is redundant data.
-  // Otherwise this will send the primary payload type without
-  // wrapping in RED.
-  if (header_length_bytes == kRedLastHeaderLength) {
-    header_length_bytes = 0;
-  }
+  // Allocate room for RFC 2198 header.
   encoded->SetSize(header_length_bytes);
 
   // Iterate backwards and append the data.
@@ -148,17 +143,15 @@ AudioEncoder::EncodedInfo AudioEncoderCopyRed::EncodeImpl(
   // `info` will be implicitly cast to an EncodedInfoLeaf struct, effectively
   // discarding the (empty) vector of redundant information. This is
   // intentional.
-  if (header_length_bytes > 0) {
+  if (header_length_bytes > kRedHeaderLength) {
     info.redundant.push_back(info);
     RTC_DCHECK_EQ(info.speech,
                   info.redundant[info.redundant.size() - 1].speech);
   }
 
   encoded->AppendData(primary_encoded_);
-  if (header_length_bytes > 0) {
-    RTC_DCHECK_EQ(header_offset, header_length_bytes - 1);
-    encoded->data()[header_offset] = info.payload_type;
-  }
+  RTC_DCHECK_EQ(header_offset, header_length_bytes - 1);
+  encoded->data()[header_offset] = info.payload_type;
 
   // Shift the redundant encodings.
   auto rit = redundant_encodings_.rbegin();
@@ -172,9 +165,7 @@ AudioEncoder::EncodedInfo AudioEncoderCopyRed::EncodeImpl(
   it->second.SetData(primary_encoded_);
 
   // Update main EncodedInfo.
-  if (header_length_bytes > 0) {
-    info.payload_type = red_payload_type_;
-  }
+  info.payload_type = red_payload_type_;
   info.encoded_bytes = encoded->size();
   return info;
 }
diff --git a/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc b/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
index 06404ab5b6..7a90850b9e 100644
--- a/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
+++ b/modules/audio_coding/codecs/red/audio_encoder_copy_red_unittest.cc
@@ -34,6 +34,8 @@ namespace webrtc {
 
 namespace {
 static const size_t kMaxNumSamples = 48 * 10 * 2;  // 10 ms @ 48 kHz stereo.
+static const size_t kRedLastHeaderLength =
+    1;  // 1 byte RED header for the last element.
 }
 
 class AudioEncoderCopyRedTest : public ::testing::Test {
@@ -154,7 +156,7 @@ TEST_F(AudioEncoderCopyRedTest, CheckNoOutput) {
   // First call is a special case, since it does not include a secondary
   // payload.
   EXPECT_EQ(0u, encoded_info_.redundant.size());
-  EXPECT_EQ(kEncodedSize, encoded_info_.encoded_bytes);
+  EXPECT_EQ(kEncodedSize + kRedLastHeaderLength, encoded_info_.encoded_bytes);
 
   // Next call to the speech encoder will not produce any output.
   Encode();
@@ -217,7 +219,7 @@ TEST_F(AudioEncoderCopyRedTest, CheckPayloadSizes) {
   // payload.
   Encode();
   EXPECT_EQ(0u, encoded_info_.redundant.size());
-  EXPECT_EQ(1u, encoded_info_.encoded_bytes);
+  EXPECT_EQ(kRedLastHeaderLength + 1u, encoded_info_.encoded_bytes);
 
   // Second call is also special since it does not include a tertiary
   // payload.
@@ -329,9 +331,10 @@ TEST_F(AudioEncoderCopyRedTest, CheckPayloads) {
   // First call is a special case, since it does not include a secondary
   // payload.
   Encode();
-  EXPECT_EQ(kPayloadLenBytes, encoded_info_.encoded_bytes);
+  EXPECT_EQ(kRedLastHeaderLength + kPayloadLenBytes,
+            encoded_info_.encoded_bytes);
   for (size_t i = 0; i < kPayloadLenBytes; ++i) {
-    EXPECT_EQ(i, encoded_.data()[i]);
+    EXPECT_EQ(i, encoded_.data()[kRedLastHeaderLength + i]);
   }
 
   for (int j = 0; j < 1; ++j) {