From 04192362e5295f963dee2acedef38bf72d58e571 Mon Sep 17 00:00:00 2001
From: "Pohsiang (John) Hsu" <pohhsu@microsoft.com>
Date: Thu, 18 Sep 2025 15:22:25 -0700
Subject: [PATCH] mediafoundation: return adjusted LTR frame (need to remove
 one for short term)

Reviewed-by: Yubo Xie <yuboxie@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37479>
---
 src/gallium/frontends/mediafoundation/codecapi.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/gallium/frontends/mediafoundation/codecapi.cpp b/src/gallium/frontends/mediafoundation/codecapi.cpp
index 981969ad7d8..ffeec3985bb 100644
--- a/src/gallium/frontends/mediafoundation/codecapi.cpp
+++ b/src/gallium/frontends/mediafoundation/codecapi.cpp
@@ -675,7 +675,14 @@ CDX12EncHMFT::GetParameterValues( const GUID *Api, VARIANT **Values, ULONG *Valu
       }
       else if( *Api == CODECAPI_AVEncVideoLTRBufferControl )
       {
-         *ValuesCount = m_EncoderCapabilities.m_uiMaxHWSupportedLongTermReferences + 1;
+         // reserve one dpb spot for short term reference frame.
+         // when m_EncoderCapabilities.m_uiMaxHWSupportedLongTermReferences = m_EncoderCapabilities.m_uiMaxHWSupportedDPBCapacity, we subtract one.
+         ULONG numSupportedLTR = m_EncoderCapabilities.m_uiMaxHWSupportedLongTermReferences;
+         if( numSupportedLTR > 0 && numSupportedLTR == m_EncoderCapabilities.m_uiMaxHWSupportedDPBCapacity )
+         {
+            numSupportedLTR -= 1;
+         }
+         *ValuesCount = numSupportedLTR + 1;
          CHECKNULL_GOTO( *Values = (VARIANT *) CoTaskMemAlloc( ( *ValuesCount ) * sizeof( VARIANT ) ), E_OUTOFMEMORY, done );
          for( ULONG i = 0; i < *ValuesCount; i++ )
          {