core(audio,frames): fix .bin replay pacing drift and lag

Author: arancormonk

include/dsd-neo/core/state.h

@@ -772,8 +772,9 @@ struct dsd_state {
     uint8_t p25_call_is_packet[2]; // 1 if call/service marked as packet (data), else 0
 
     //experimental symbol file capture read throttle
-    int symbol_throttle; //throttle speed
-    int use_throttle;    //only use throttle if set to 1
+    int symbol_throttle;                     //throttle speed
+    int use_throttle;                        //only use throttle if set to 1
+    uint64_t symbol_replay_next_deadline_ns; //0 when uninitialized
 
     //dmr trunking stuff
     int dmr_rest_channel;

src/core/audio/dsd_audio.c

@@ -811,6 +811,11 @@ openAudioInDevice(dsd_opts* opts, dsd_state* state) {
         dsd_net_audio_input_hook_udp_stop(opts);
     }
     dsd_opts_reset_pcm_input_state(opts);
+    if (state) {
+        /* .bin symbol replay can opt into paced playback; reset before probing input type. */
+        state->use_throttle = 0;
+        state->symbol_replay_next_deadline_ns = 0;
+    }
 
     char* extension;
     const char ch = '.';
@@ -1002,6 +1007,10 @@ openAudioInDevice(dsd_opts* opts, dsd_state* state) {
                 return -1;
             }
             opts->audio_in_type = AUDIO_IN_SYMBOL_BIN; //symbol capture bin files
+            if (state) {
+                state->use_throttle = 1;
+                state->symbol_replay_next_deadline_ns = 0;
+            }
         } else {
             opts->audio_in_type = AUDIO_IN_PULSE;
         }

src/core/frames/dsd_dibit.c

@@ -41,6 +41,52 @@
 #include "dsd-neo/core/opts_fwd.h"
 #include "dsd-neo/core/state_fwd.h"
 
+static void
+throttle_symbol_bin_replay(dsd_opts* opts, dsd_state* state) {
+    if (!opts || !state || state->use_throttle != 1) {
+        return;
+    }
+
+    /* Keep legacy microsecond override support when explicitly configured. */
+    if (state->symbol_throttle > 0) {
+        dsd_sleep_us((uint64_t)state->symbol_throttle);
+        return;
+    }
+
+    int input_rate_hz = dsd_opts_current_input_timing_rate(opts);
+    if (input_rate_hz <= 0) {
+        input_rate_hz = SAMPLE_RATE_IN;
+    }
+
+    int sps = state->samplesPerSymbol;
+    if (sps <= 0) {
+        sps = 10;
+    }
+
+    uint64_t period_ns = ((uint64_t)sps * 1000000000ULL) / (uint64_t)input_rate_hz;
+    if (period_ns == 0ULL) {
+        dsd_sleep_ms(0U);
+        return;
+    }
+
+    uint64_t now_ns = dsd_time_monotonic_ns();
+    uint64_t deadline_ns = state->symbol_replay_next_deadline_ns;
+    if (deadline_ns == 0ULL) {
+        state->symbol_replay_next_deadline_ns = now_ns + period_ns;
+        return;
+    }
+
+    if (now_ns < deadline_ns) {
+        dsd_sleep_ns(deadline_ns - now_ns);
+    } else if ((now_ns - deadline_ns) > 250000000ULL) {
+        /* Rebase pacing after long scheduler stalls/debug pauses. */
+        state->symbol_replay_next_deadline_ns = now_ns + period_ns;
+        return;
+    }
+
+    state->symbol_replay_next_deadline_ns = deadline_ns + period_ns;
+}
+
 static void
 print_datascope(dsd_opts* opts, dsd_state* state, const float* sbuf2, int count) {
     int i, j, o;
@@ -766,9 +812,7 @@ get_dibit_and_analog_signal(dsd_opts* opts, dsd_state* state, int* out_analog_si
     if (opts->audio_in_type == AUDIO_IN_SYMBOL_BIN) {
         //assign dibit from last symbol/dibit read from capture bin
         dibit = state->symbolc;
-        if (state->use_throttle == 1) {
-            dsd_sleep_ms(0); /* yield CPU */
-        }
+        throttle_symbol_bin_replay(opts, state);
     }
 
     //symbol/dibit file capture/writing
@@ -858,9 +902,7 @@ getDibitAndSoftSymbol(dsd_opts* opts, dsd_state* state, float* out_soft_symbol)
 
     if (opts->audio_in_type == AUDIO_IN_SYMBOL_BIN) {
         dibit = state->symbolc;
-        if (state->use_throttle == 1) {
-            dsd_sleep_ms(0); /* yield CPU */
-        }
+        throttle_symbol_bin_replay(opts, state);
     }
 
     if (opts->symbol_out_f) {

src/core/util/dsd_init.c

@@ -767,8 +767,9 @@ initState(dsd_state* state) {
     state->p25_vc_cqpsk_override = -1;
 
     //experimental symbol file capture read throttle
-    state->symbol_throttle = 100; //throttle speed
-    state->use_throttle = 0;      //only use throttle if set to 1
+    state->symbol_throttle = 0; //0 = auto pace from symbol timing
+    state->use_throttle = 0;    //only use throttle if set to 1
+    state->symbol_replay_next_deadline_ns = 0;
 
     state->p2_scramble_offset = 0;
     state->p2_vch_chan_num = 0;