Testing

dialer/android/app/src/main/cpp/audio-hijack/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.22)
+project(cap_pcm C)
+
+# Fetch TinyALSA from GitHub
+include(FetchContent)
+FetchContent_Declare(
+        tinyalsa
+        GIT_REPOSITORY https://github.com/tinyalsa/tinyalsa.git
+        GIT_TAG        v2.0.0
+)
+FetchContent_MakeAvailable(tinyalsa)
+
+# Your executable
+add_executable(cap_pcm cap_pcm.c)
+
+# Tell the compiler where to find the headers
+target_include_directories(cap_pcm PRIVATE
+        ${tinyalsa_SOURCE_DIR}/include
+)
+
+# Link against the library target defined by TinyALSA’s CMakeLists.txt
+target_link_libraries(cap_pcm PRIVATE tinyalsa)

dialer/android/app/src/main/cpp/audio-hijack/cap_pcm.c

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+#include <tinyalsa/asoundlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main(int argc, char** argv) {
+    unsigned rate = (argc > 1) ? atoi(argv[1]) : 8000;
+    struct pcm_config cfg = {
+            .channels = 1,
+            .rate     = rate,
+            .format   = PCM_FORMAT_S16_LE,
+            .period_size = 160,   // 20 ms @ 8 kHz
+            .period_count = 4,
+    };
+    struct pcm *pcm = pcm_open(0, 0, PCM_IN, &cfg);   // card 0, device 0, CAPTURE
+    if (!pcm || !pcm_is_ready(pcm)) return 1;
+
+    unsigned char buf[320];  // 160 samples * 2 bytes
+    while (1) {
+        if (pcm_read(pcm, buf, sizeof(buf)) == 0)
+            fwrite(buf, 1, sizeof(buf), stdout);      // stream to pipe
+        else
+            break;
+    }
+    pcm_close(pcm);
+    return 0;
+}