From 05b58ad77e79efc5b4750f40b5092f945f0fff4d Mon Sep 17 00:00:00 2001
From: Philipp Hancke <phancke@microsoft.com>
Date: Mon, 14 Nov 2022 12:21:29 +0100
Subject: [PATCH] video_layer_allocation: clean up unused code

remove unused support for more than four spatial layer descriptions
of temporal layers

BUG=webrtc:12000

Change-Id: I087bcd020897898636bdf9c838abafa8c73c53f3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/281320
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38646}
---
 .../rtp_video_layers_allocation_extension.cc  | 24 ++++++-------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/modules/rtp_rtcp/source/rtp_video_layers_allocation_extension.cc b/modules/rtp_rtcp/source/rtp_video_layers_allocation_extension.cc
index 5172ed4ce7..d44cb56205 100644
--- a/modules/rtp_rtcp/source/rtp_video_layers_allocation_extension.cc
+++ b/modules/rtp_rtcp/source/rtp_video_layers_allocation_extension.cc
@@ -184,16 +184,12 @@ bool RtpVideoLayersAllocationExtension::Write(
   }
   ++write_at;
 
-  {  // Number of temporal layers.
+  {  // Number of temporal layers per spatial layer (at most kMaxSpatialIds).
+    static_assert(VideoLayersAllocation::kMaxSpatialIds == 4);
     int bit_offset = 8;
     *write_at = 0;
     for (const auto& layer : allocation.active_spatial_layers) {
-      if (bit_offset == 0) {
-        bit_offset = 6;
-        *++write_at = 0;
-      } else {
-        bit_offset -= 2;
-      }
+      bit_offset -= 2;
       *write_at |=
           ((layer.target_bitrate_per_temporal_layer.size() - 1) << bit_offset);
     }
@@ -269,8 +265,9 @@ bool RtpVideoLayersAllocationExtension::Parse(
     return false;
   }
 
-  // Read number of temporal layers,
-  // Create `allocation->active_spatial_layers` while iterating though it.
+  // Read number of temporal layers per spatial layer (at most kMaxSpatialIds),
+  // create `allocation->active_spatial_layers` while iterating though it.
+  static_assert(VideoLayersAllocation::kMaxSpatialIds == 4);
   int bit_offset = 8;
   for (int stream_idx = 0; stream_idx < num_rtp_streams; ++stream_idx) {
     for (int sid = 0; sid < VideoLayersAllocation::kMaxSpatialIds; ++sid) {
@@ -278,14 +275,7 @@ bool RtpVideoLayersAllocationExtension::Parse(
         continue;
       }
 
-      if (bit_offset == 0) {
-        bit_offset = 6;
-        if (++read_at == end) {
-          return false;
-        }
-      } else {
-        bit_offset -= 2;
-      }
+      bit_offset -= 2;
       int num_temporal_layers = 1 + ((*read_at >> bit_offset) & 0b11);
       allocation->active_spatial_layers.emplace_back();
       auto& layer = allocation->active_spatial_layers.back();