libldac-dec: fix ldacBT_init_handle_decode channel config

The decoder init passes UNSET (-1) as channel_config_index to
ldaclib_set_config_info because the struct fields are assigned after
the call instead of before. Fails with LDAC_ERR_ASSERT_CHANNEL_CONFIG
(533) on every invocation.

This breaks LDAC A2DP in PipeWire: codec_init fails, the bluetooth
sink never starts, and all streams routed to it stay stuck in [init]
with no audio and no user-visible error.

Upstream PR: O2C14/libldac-dec#2

Author: Mic92

pkgs/by-name/li/libldac-dec/fix-init-decode.patch

@@ -0,0 +1,56 @@
+From 1c76d1d65e6da0a63b8bc9329debcf2ff1516143 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
+Date: Mon, 30 Mar 2026 11:40:28 +0200
+Subject: [PATCH] Fix use-before-init in ldacBT_init_handle_decode
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+ldacBT_close_handle() resets cci/frmlen/frm_status to UNSET (-1).
+The subsequent ldaclib_set_config_info() was called with these stale
+struct members instead of the freshly computed local values, causing
+LDAC_ERR_ASSERT_CHANNEL_CONFIG (533) on every invocation regardless
+of the channel mode passed in.
+
+Move the struct assignments before the ldaclib_set_config_info() call
+so it receives valid configuration.
+
+This was breaking LDAC A2DP in PipeWire: the decoder handle fails to
+initialise during codec_init(), which aborts the entire codec setup
+and leaves the bluetooth sink unable to start.
+
+Signed-off-by: Jörg Thalheim <joerg@thalheim.io>
+---
+ src/ldacBT_api.o.c | 9 ++++-----
+ 1 file changed, 4 insertions(+), 5 deletions(-)
+
+diff --git a/src/ldacBT_api.o.c b/src/ldacBT_api.o.c
+index f4cb9cd..a396a14 100644
+--- a/src/ldacBT_api.o.c
++++ b/src/ldacBT_api.o.c
+@@ -165,6 +165,10 @@ LDACBT_API int ldacBT_init_handle_decode(
+   // tbl_ldacbt_config[0].frmlen_1ch;
+   // frmlen = 165 * channel - LDACBT_FRMHDRBYTES;
+   frmlen = tbl_ldacbt_config[0].frmlen_1ch * channel - LDACBT_FRMHDRBYTES;
++  hLdacBT->frmlen = frmlen;
++  hLdacBT->cm = cm;
++  hLdacBT->cci = cci;
++  hLdacBT->frm_status = 0;
+   /* Set Configuration Information */
+   result = ldaclib_set_config_info(
+       hLdacBT->hLDAC, hLdacBT->sfid, hLdacBT->cci, hLdacBT->frmlen, hLdacBT->frm_status);
+@@ -174,11 +178,6 @@ LDACBT_API int ldacBT_init_handle_decode(
+   } else if (result != LDAC_S_OK) {
+     hLdacBT->error_code_api = LDACBT_GET_LDACLIB_ERROR_CODE;
+   }
+-  hLdacBT->frmlen = frmlen;
+-  hLdacBT->cm = cm;
+-  hLdacBT->cci = cci;
+-  hLdacBT->frm_status = 0;
+-  hLdacBT->sfid = sfid;
+   result = ldaclib_init_decode(hLdacBT->hLDAC, nshift);
+   if (LDAC_FAILED(result)) {
+     hLdacBT->error_code_api = LDACBT_GET_LDACLIB_ERROR_CODE;
+-- 
+2.53.0
+

pkgs/by-name/li/libldac-dec/package.nix

@@ -17,6 +17,14 @@ stdenv.mkDerivation {
     hash = "sha256-pdeEtQXxL2pd9qTfLOEmPDn3POgo5qxRqbK807WN98s=";
   };
 
+  patches = [
+    # ldacBT_init_handle_decode passes UNSET (-1) cci/frmlen to
+    # ldaclib_set_config_info, failing with LDAC_ERR_ASSERT_CHANNEL_CONFIG
+    # on every call. Breaks LDAC A2DP in pipewire.
+    # https://github.com/O2C14/libldac-dec/pull/2
+    ./fix-init-decode.patch
+  ];
+
   nativeBuildInputs = [ cmake ];
 
   # Upstream CMakeLists.txt doesn't have install rules