From 8eafe279555c8646fb82b965e0fe138ae6b17f23 Mon Sep 17 00:00:00 2001
From: Mark Thompson <129641948+NotherNgineer@users.noreply.github.com>
Date: Fri, 21 Jul 2023 11:50:00 -0500
Subject: [PATCH] Minor Replay & GPS baseband optimizations (#1289)

* No need to scale progress now that widget is fixed
* Use memcpy vs byte copy, elim progress scaling, correct comments
* Minor optimization in C16->C8 conversion
* Only copy bytes actually read from file
---
 firmware/application/apps/gps_sim_app.cpp |  4 +--
 firmware/baseband/proc_gps_sim.cpp        | 35 +++++++++++------------
 firmware/baseband/proc_replay.cpp         |  2 +-
 3 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/firmware/application/apps/gps_sim_app.cpp b/firmware/application/apps/gps_sim_app.cpp
index bc8c7e2f..02306ddb 100644
--- a/firmware/application/apps/gps_sim_app.cpp
+++ b/firmware/application/apps/gps_sim_app.cpp
@@ -65,12 +65,12 @@ void GpsSimAppView::on_file_changed(const fs::path& new_file_path) {
         field_frequency.set_value(metadata->center_frequency);
         sample_rate = metadata->sample_rate;
     } else {
-        sample_rate = 500000;
+        sample_rate = 2600000;
     }
 
     // UI Fixup.
     text_sample_rate.set(unit_auto_scale(sample_rate, 3, 1) + "Hz");
-    progressbar.set_max(file_size / 1024);
+    progressbar.set_max(file_size);
     text_filename.set(truncate(file_path.filename().string(), 12));
 
     auto duration = ms_duration(file_size, sample_rate, 2);
diff --git a/firmware/baseband/proc_gps_sim.cpp b/firmware/baseband/proc_gps_sim.cpp
index 860da216..d4ab50d2 100644
--- a/firmware/baseband/proc_gps_sim.cpp
+++ b/firmware/baseband/proc_gps_sim.cpp
@@ -42,34 +42,33 @@ ReplayProcessor::ReplayProcessor() {
 }
 
 void ReplayProcessor::execute(const buffer_c8_t& buffer) {
-    /* 4MHz, 2048 samples */
+    /* 2.6MHz, 2048 samples */
 
     if (!configured) return;
 
-    // File data is in C16 format, we need C8
-    // File samplerate is 500kHz, we're at 4MHz
-    // iq_buffer can only be 512 C16 samples (RAM limitation)
-    // To fill up the 2048-sample C8 buffer, we need:
-    // 2048 samples * 2 bytes per sample = 4096 bytes
-    // Since we're oversampling by 4M/500k = 8, we only need 2048/8 = 256 samples from the file and duplicate them 8 times each
-    // So 256 * 4 bytes per sample (C16) = 1024 bytes from the file
-    if (stream) {                                                             // sizeof(*buffer.p) = sizeof(C8) = 2*int8 = 2 bytes //buffer.count = 2048
-        const size_t bytes_to_read = sizeof(*buffer.p) * 1 * (buffer.count);  // *2 (C16), /8 (oversampling) should be == 1024
-        bytes_read += stream->read(iq_buffer.p, bytes_to_read);
-    }
+    // File data is in C8 format, which is what we need
+    // File samplerate is 2.6MHz, which is what we need
+    // To fill up the 2048-sample C8 buffer @ 2 bytes per sample = 4096 bytes
+    if (stream) {
+        const size_t bytes_to_read = sizeof(*buffer.p) * 1 * (buffer.count);
+        size_t bytes_read_this_iteration = stream->read(iq_buffer.p, bytes_to_read);
+        bytes_read += bytes_read_this_iteration;
 
-    // Fill and "stretch"
-    for (size_t i = 0; i < buffer.count; i++) {
-        auto re_out = iq_buffer.p[i].real();
-        auto im_out = iq_buffer.p[i].imag();
-        buffer.p[i] = {(int8_t)re_out, (int8_t)im_out};
+        // NB: Couldn't we have just read the data into buffer.p to start with, or some DMA/cache coherency concern?
+        //
+        // for (size_t i = 0; i < buffer.count; i++) {
+        //     auto re_out = iq_buffer.p[i].real();
+        //     auto im_out = iq_buffer.p[i].imag();
+        //     buffer.p[i] = {(int8_t)re_out, (int8_t)im_out};
+        // }
+        memcpy(buffer.p, iq_buffer.p, bytes_read_this_iteration);  // memcpy should be more efficient than 1 byte at a time
     }
 
     spectrum_samples += buffer.count;
     if (spectrum_samples >= spectrum_interval_samples) {
         spectrum_samples -= spectrum_interval_samples;
 
-        txprogress_message.progress = bytes_read / 1024;  // Inform UI about progress
+        txprogress_message.progress = bytes_read;  // Inform UI about progress
 
         txprogress_message.done = false;
         shared_memory.application_queue.push(txprogress_message);
diff --git a/firmware/baseband/proc_replay.cpp b/firmware/baseband/proc_replay.cpp
index 52378fab..33bebc3a 100644
--- a/firmware/baseband/proc_replay.cpp
+++ b/firmware/baseband/proc_replay.cpp
@@ -59,7 +59,7 @@ void ReplayProcessor::execute(const buffer_c8_t& buffer) {
 
     // Fill and "stretch"
     for (size_t i = 0; i < buffer.count; i++) {
-        if (i & 3) {
+        if (i & 7) {
             buffer.p[i] = buffer.p[i - 1];
         } else {
             auto re_out = iq_buffer.p[i >> 3].real() >> 8;