cisco · niw · Jun 17, 2026
diff --git a/codec/decoder/core/src/manage_dec_ref.cpp b/codec/decoder/core/src/manage_dec_ref.cpp
@@ -557,7 +557,7 @@ int32_t WelsReorderRefList2 (PWelsDecoderContext pCtx) {
           iPredFrameNum = pRefPicListReorderSyn->sReorderingSyn[listIdx][i].uiLongTermPicNum;
           for (j = 0; j < iLongRefCount; j++) {
             if (ppLongRefList[j] != NULL) {
-              if (ppLongRefList[j]->uiLongTermPicNum == (uint32_t)iPredFrameNum) {
+              if (ppLongRefList[j]->iLongTermFrameIdx == iPredFrameNum) {
                 ppRefList[iCount++] = ppLongRefList[j];
                 break;
               }
@@ -566,7 +566,7 @@ int32_t WelsReorderRefList2 (PWelsDecoderContext pCtx) {
           k = iCount;
           for (j = k; j <= iRefCount; j++) {
             if (ppRefList[j] != NULL) {
-              if (!ppRefList[j]->bIsLongRef || ppRefList[j]->uiLongTermPicNum != (uint32_t)iPredFrameNum)
+              if (!ppRefList[j]->bIsLongRef || ppRefList[j]->iLongTermFrameIdx != iPredFrameNum)
                 ppRefList[k++] = ppRefList[j];
             }
           }

diff --git a/res/ltr_reorder_high_cabac.264 b/res/ltr_reorder_high_cabac.264
diff --git a/test/api/decoder_test.cpp b/test/api/decoder_test.cpp
@@ -139,6 +139,7 @@ static const FileParam kFileParamArray[] = {
   {"res/VID_1280x544_cavlc_temporal_direct.264", "33bfa44b4a3c87fe28354cace1d4b99a03d2967d"},
   {"res/VID_1280x720_cavlc_temporal_direct.264", "4face6b5d73a378b6e564a831b49311c230158e4"},
   {"res/VID_1920x1080_cavlc_temporal_direct.264", "b35dc99604ea2a1fda5b84d1b9098cb7565dec8f"},
+  {"res/ltr_reorder_high_cabac.264", "f496a84291950422de2620e6e022a4ac47b099f1"},
 };
 
 INSTANTIATE_TEST_CASE_P (DecodeFile, DecoderOutputTest,

diff --git a/test/build/win32/codec_ut/codec_unittest.vcproj b/test/build/win32/codec_ut/codec_unittest.vcproj
@@ -726,6 +726,42 @@
 					/>
 				</FileConfiguration>
 			</File>
+			<File
+				RelativePath="..\..\..\decoder\DecUT_RefListReorder.cpp"
+				>
+				<FileConfiguration
+					Name="Debug|Win32"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						AdditionalIncludeDirectories="..\..\..\..\codec\api\wels;..\..\..\..\gtest\include;..\..\..\;..\..\..\..\codec\decoder\plus\inc;..\..\..\..\codec\common\inc;..\..\..\..\codec\decoder\core\inc;$(NOINHERIT)"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Debug|x64"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						AdditionalIncludeDirectories="..\..\..\..\codec\api\wels;..\..\..\..\gtest\include;..\..\..\;..\..\..\..\codec\decoder\plus\inc;..\..\..\..\codec\common\inc;..\..\..\..\codec\decoder\core\inc;$(NOINHERIT)"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Release|Win32"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						AdditionalIncludeDirectories="..\..\..\..\codec\api\wels;..\..\..\..\gtest\include;..\..\..\;..\..\..\..\codec\decoder\plus\inc;..\..\..\..\codec\common\inc;..\..\..\..\codec\decoder\core\inc;$(NOINHERIT)"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Release|x64"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						AdditionalIncludeDirectories="..\..\..\..\codec\api\wels;..\..\..\..\gtest\include;..\..\..\;..\..\..\..\codec\decoder\plus\inc;..\..\..\..\codec\common\inc;..\..\..\..\codec\decoder\core\inc;$(NOINHERIT)"
+					/>
+				</FileConfiguration>
+			</File>
 		</Filter>
 		<Filter
 			Name="processing"

diff --git a/test/decoder/DecUT_RefListReorder.cpp b/test/decoder/DecUT_RefListReorder.cpp
@@ -0,0 +1,89 @@
+#include <gtest/gtest.h>
+#include <cstring>
+#include "decoder_context.h"
+#include "manage_dec_ref.h"
+
+using namespace WelsDec;
+
+namespace {
+
+const int kLongRefCount = 3;
+const int kTargetFrameIdx = 2; // request the long-term reference with iLongTermFrameIdx == 2
+
+class RefListReorderTest : public ::testing::Test {
+ protected:
+  virtual void SetUp() {
+    m_pCtx = new SWelsDecoderContext;
+    m_pDqLayer = new SDqLayer;
+    m_pReorder = new SRefPicListReorderSyn;
+    m_pSps = new SSps;
+    memset (m_pCtx, 0, sizeof (SWelsDecoderContext));
+    memset (m_pDqLayer, 0, sizeof (SDqLayer));
+    memset (m_pReorder, 0, sizeof (SRefPicListReorderSyn));
+    memset (m_pSps, 0, sizeof (SSps));
+    memset (m_aPics, 0, sizeof (m_aPics));
+
+    // Three long-term references with distinct frame indices but, as MMCO-6 marking produces,
+    // an identical (zero) uiLongTermPicNum.
+    for (int i = 0; i < kLongRefCount; ++i) {
+      m_aPics[i].bIsLongRef = true;
+      m_aPics[i].iLongTermFrameIdx = i;
+      m_aPics[i].uiLongTermPicNum = 0;
+    }
+
+    // Reference list starts in default frame-index order [idx0, idx1, idx2].
+    SRefPic& sRefPic = m_pCtx->sRefPic;
+    for (int i = 0; i < kLongRefCount; ++i) {
+      sRefPic.pLongRefList[LIST_0][i] = &m_aPics[i];
+      sRefPic.pRefList[LIST_0][i] = &m_aPics[i];
+    }
+    sRefPic.uiLongRefCount[LIST_0] = kLongRefCount;
+    sRefPic.uiShortRefCount[LIST_0] = 0;
+    sRefPic.uiRefCount[LIST_0] = 0;
+
+    // A single long-term reorder command requesting long_term_pic_num == kTargetFrameIdx,
+    // terminated by idc == 3.
+    m_pReorder->bRefPicListReorderingFlag[LIST_0] = true;
+    m_pReorder->sReorderingSyn[LIST_0][0].uiReorderingOfPicNumsIdc = 2;
+    m_pReorder->sReorderingSyn[LIST_0][0].uiLongTermPicNum = kTargetFrameIdx;
+    m_pReorder->sReorderingSyn[LIST_0][1].uiReorderingOfPicNumsIdc = 3;
+
+    m_pDqLayer->pRefPicListReordering = m_pReorder;
+    PSliceHeader pSliceHeader = &m_pDqLayer->sLayerInfo.sSliceInLayer.sSliceHeaderExt.sSliceHeader;
+    pSliceHeader->iFrameNum = 5;
+    pSliceHeader->uiRefCount[LIST_0] = kLongRefCount;
+    pSliceHeader->pSps = m_pSps;
+    m_pSps->uiLog2MaxFrameNum = 4;
+
+    m_pCtx->pCurDqLayer = m_pDqLayer;
+    m_pCtx->eSliceType = P_SLICE;
+    m_pCtx->iPicQueueNumber = MAX_REF_PIC_COUNT;
+  }
+
+  virtual void TearDown() {
+    delete m_pSps;
+    delete m_pReorder;
+    delete m_pDqLayer;
+    delete m_pCtx;
+  }
+
+  PWelsDecoderContext m_pCtx;
+  PDqLayer m_pDqLayer;
+  PRefPicListReorderSyn m_pReorder;
+  PSps m_pSps;
+  SPicture m_aPics[kLongRefCount];
+};
+
+// The long-term reorder command asks for the reference with LongTermFrameIdx == 2 to be placed
+// first.
+TEST_F (RefListReorderTest, LongTermReorderMatchesByFrameIdx) {
+  int32_t iRet = WelsReorderRefList2 (m_pCtx);
+  ASSERT_EQ (iRet, ERR_NONE);
+
+  PPicture pFirst = m_pCtx->sRefPic.pRefList[LIST_0][0];
+  ASSERT_TRUE (pFirst != NULL);
+  EXPECT_TRUE (pFirst->bIsLongRef);
+  EXPECT_EQ (pFirst->iLongTermFrameIdx, kTargetFrameIdx);
+}
+
+} // anonymous namespace
diff --git a/test/decoder/meson.build b/test/decoder/meson.build
@@ -7,6 +7,7 @@ test_sources = [
   'DecUT_IntraPrediction.cpp',
   'DecUT_ParseSyntax.cpp',
   'DecUT_PredMv.cpp',
+  'DecUT_RefListReorder.cpp',
 ]
 
 e = executable('test_decoder', test_sources,

diff --git a/test/decoder/targets.mk b/test/decoder/targets.mk
@@ -11,6 +11,7 @@ DECODER_UNITTEST_CPP_SRCS=\
 	$(DECODER_UNITTEST_SRCDIR)/DecUT_IntraPrediction.cpp\
 	$(DECODER_UNITTEST_SRCDIR)/DecUT_ParseSyntax.cpp\
 	$(DECODER_UNITTEST_SRCDIR)/DecUT_PredMv.cpp\
+	$(DECODER_UNITTEST_SRCDIR)/DecUT_RefListReorder.cpp\
 
 DECODER_UNITTEST_OBJS += $(DECODER_UNITTEST_CPP_SRCS:.cpp=.$(OBJ))