From 68f05d2313791d08f92473306f4e92d767bd1855 Mon Sep 17 00:00:00 2001
From: Armin <armin@raumschiff>
Date: Fri, 3 Jul 2026 23:24:25 +0200
Subject: [PATCH] fix: use 120sec window in the middle of the file, not from
 the start when not using -F; further alg. bugfixes

---
 tcd.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/tcd.c b/tcd.c
index d851142..b615e6a 100644
--- a/tcd.c
+++ b/tcd.c
@@ -23,7 +23,7 @@
 
 #define FFT_SIZE_DEFAULT  4096
 #define THRESHOLD_DEFAULT 50
-#define MAX_ANALYSIS_SECS 60
+#define MAX_ANALYSIS_SECS 120
 #define OVERLAP_FACTOR    2
 
 #define ANSI_RESET   "\033[0m"
@@ -1082,6 +1082,12 @@ static int process_file(const char *filename, const Options *opts)
     int max_frames = opts->full ? INT_MAX : sample_rate * opts->max_secs;
     int total_frames = 0;
 
+    if (!opts->full && fmt_ctx->duration > 0 && fmt_ctx->duration != AV_NOPTS_VALUE) {
+        int64_t seek_ts = fmt_ctx->duration / 2;
+        if (av_seek_frame(fmt_ctx, -1, seek_ts, AVSEEK_FLAG_BACKWARD) >= 0)
+            avcodec_flush_buffers(codec_ctx);
+    }
+
     float *ring = calloc(opts->fft_size * channels, sizeof(float));
     int ring_pos = 0;
 
@@ -1183,8 +1189,12 @@ static int process_file(const char *filename, const Options *opts)
             double expected_min = 0.90;
             if (bitrate > 0 && bitrate < 192000) expected_min = 0.75;
             else if (bitrate > 0 && bitrate < 256000) expected_min = 0.85;
-            if (cutoff_ratio > 0 && cutoff_ratio < expected_min - 0.08)
-                upscaled = 1;
+            if (cutoff_ratio > 0 && cutoff_ratio < expected_min - 0.08) {
+                if (effective_cutoff > 0 && steepness / effective_cutoff > 0.30)
+                    upscaled = 0;
+                else
+                    upscaled = 1;
+            }
         }
 
         render_visual_spectrum(
@@ -1244,8 +1254,12 @@ static int process_file(const char *filename, const Options *opts)
         if (bitrate > 0 && bitrate < 192000) expected_min = 0.75;
         else if (bitrate > 0 && bitrate < 256000) expected_min = 0.85;
 
-        if (cutoff_ratio > 0 && cutoff_ratio < expected_min - 0.08)
-            upscaled = 1;
+        if (cutoff_ratio > 0 && cutoff_ratio < expected_min - 0.08) {
+            if (effective_cutoff > 0 && steepness / effective_cutoff > 0.30)
+                upscaled = 0;
+            else
+                upscaled = 1;
+        }
 
         if (upscaled) {
             printf(ANSI_YELLOW "UPSCALED" ANSI_RESET " (re-encoded from a lower-bitrate source)\n");