From 3f9ae1ee1045983bd225131fb34de03b5000b692 Mon Sep 17 00:00:00 2001
From: Niklas Carlsson <niklasc@axis.com>
Date: Mon, 29 Sep 2025 12:09:57 +0200
Subject: [PATCH] filter-graph: allow 8 channels in max plugin

Mimic the same channel behavior as for other plugins that allows
for 8 channels, such as Mixer and Mult.
---
 spa/plugins/filter-graph/plugin_builtin.c | 61 +++++++++++++++++------
 src/modules/module-filter-chain.c         |  7 ++-
 2 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/spa/plugins/filter-graph/plugin_builtin.c b/spa/plugins/filter-graph/plugin_builtin.c
index 955c6442d..647c9a51b 100644
--- a/spa/plugins/filter-graph/plugin_builtin.c
+++ b/spa/plugins/filter-graph/plugin_builtin.c
@@ -2155,24 +2155,33 @@ static const struct spa_fga_descriptor param_eq_desc = {
 static void max_run(void * Instance, unsigned long SampleCount)
 {
 	struct builtin *impl = Instance;
-	float *out = impl->port[0], *in1 = impl->port[1], *in2 = impl->port[2];
-	unsigned long n;
+	float *out = impl->port[0];
+	float *src[8];
+	unsigned long n, p, n_srcs = 0;
 
 	if (out == NULL)
 		return;
 
-	if (in1 != NULL && in2 != NULL) {
-		for (n = 0; n < SampleCount; n++)
-			out[n] = SPA_MAX(in1[n], in2[n]);
-	} else if (in1 != NULL) {
-		for (n = 0; n < SampleCount; n++)
-			out[n] = in1[n];
-	} else if (in2 != NULL) {
-		for (n = 0; n < SampleCount; n++)
-			out[n] = in2[n];
+	for (p = 1; p < 9; p++) {
+		if (impl->port[p] != NULL)
+			src[n_srcs++] = impl->port[p];
+	}
+
+	if (n_srcs == 0) {
+		spa_memzero(out, SampleCount * sizeof(float));
+	} else if (n_srcs == 1) {
+		spa_memcpy(out, src[0], SampleCount * sizeof(float));
 	} else {
-		for (n = 0; n < SampleCount; n++)
-			out[n] = 0.0f;
+		for (p = 0; p < n_srcs; p++) {
+			if (p == 0) {
+				for (n = 0; n < SampleCount; n++)
+					out[n] = SPA_MAX(src[p][n], src[p + 1][n]);
+				p++;
+			} else {
+				for (n = 0; n < SampleCount; n++)
+					out[n] = SPA_MAX(out[n], src[p][n]);
+			}
+		}
 	}
 }
 
@@ -2189,7 +2198,31 @@ static struct spa_fga_port max_ports[] = {
 	{ .index = 2,
 	  .name = "In 2",
 	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
-	}
+	},
+	{ .index = 3,
+	  .name = "In 3",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
+	{ .index = 4,
+	  .name = "In 4",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
+	{ .index = 5,
+	  .name = "In 5",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
+	{ .index = 6,
+	  .name = "In 6",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
+	{ .index = 7,
+	  .name = "In 7",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
+	{ .index = 8,
+	  .name = "In 8",
+	  .flags = SPA_FGA_PORT_INPUT | SPA_FGA_PORT_AUDIO,
+	},
 };
 
 static const struct spa_fga_descriptor max_desc = {
diff --git a/src/modules/module-filter-chain.c b/src/modules/module-filter-chain.c
index 6c2f16200..84b70d651 100644
--- a/src/modules/module-filter-chain.c
+++ b/src/modules/module-filter-chain.c
@@ -537,9 +537,12 @@ extern struct spa_handle_factory spa_filter_graph_factory;
  *
  * ### Max
  *
- * Use the `max` plugin if you need to select the max value of two channels.
+ * Use the `max` plugin if you need to select the max value of a number of input ports.
  *
- * It has two input ports "In 1" and "In 2" and one output port "Out".
+ * It has 8 input ports named "In 1" to "In 8" and one output port "Out".
+ *
+ * All input ports samples are checked to find the maximum value per sample. Unused
+ * input ports will be ignored and not cause overhead.
  *
  * ### dcblock
  *