post(devops): every player stuttered on the same video — the file was blameless (EN+ZH) + og/banner

The converted HEVC stuttered in VLC, Chrome and on an iPad (offline) while the source played fine.
Container timing was perfect (5818/5818 frame intervals at exactly 0.040000 s, no dup/backward PTS,
ctts not flat) and a full decode printed nothing. Cross-decoder SSIM found the real defect: NVDEC's
legacy av1_cuvid wrapper returns frames from the wrong timestamps - 106 of 5819 frames, SSIM down to
0.330, deterministically, roughly every 30 frames - and the HEVC output was a faithful encode of those
wrong pictures (min 0.991 against the NVDEC decode, min 0.330 against a software decode). Fix is one
line (-hwaccel cuda -hwaccel_output_format cuda -c:v av1, verified 1.000000 over 1500 frames; vp9_cuvid
unaffected). Adds the content gate (structure AND pictures, defect-shaped thresholds) to the pipeline.

scripts/banner-gen/generate.mjs

@@ -1149,6 +1149,24 @@ BANNERS['putting-a-front-door-on-an-app-you-cant-modify'] = {
   ],
 };
 
+BANNERS['every-player-stuttered-the-file-was-fine'] = {
+  titlebar: "root@media - the file was blameless",
+  lines: [
+    { t: 'prompt', text: "$" }, { t: 'cmd', text: "tsconv --file 5YkGHtaduGU" },
+    { t: 'dim', text: "container: 5818/5818 frames @ 0.040000 s" }, { t: 'dim', text: "decode: rc=0, zero errors printed" },
+    { t: 'err', text: "pictures: 106 frames wrong (SSIM 0.33)" }, { t: 'prompt', text: "$" },
+    { t: 'cmd', text: "-hwaccel cuda -c:v av1" }, { t: 'ok', text: "0 wrong frames  SSIM 1.000000" },
+    { t: 'hl', text: "gate: structure AND content, then replace" }, { t: 'dim', text: "65/65 affected files re-encoded" },
+  ],
+  flow: [
+    { n: '1', label: "decode" },
+    { n: '2', label: "encode" },
+    { n: '3', label: "verify" },
+    { n: '4', label: "content" },
+    { n: '5', label: "replace" },
+  ],
+};
+
 // ---------- read frontmatter ----------
 const postPath = join(ROOT, 'src', 'content', 'posts', `${slug}.md`);
 let category = 'devops';

scripts/og-gen/generate.mjs

@@ -349,6 +349,12 @@ TERMINALS['putting-a-front-door-on-an-app-you-cant-modify'] = `
     <div class="line"><span class="prompt">$</span><span class="cmd">docker compose up -d   (gateway takes the public port)</span><span class="fix">→ front page 200 ✓</span></div>
     <div class="line"><span class="prompt">$</span><span class="cmd">curl -s /index.html | grep -o lang=</span><span class="fix">→ zh-CN ✓</span></div>`;
 
+TERMINALS['every-player-stuttered-the-file-was-fine'] = `
+    <div class="line"><span class="prompt">$</span><span class="cmd">ffmpeg -v error -i out.mp4 -f null -   ->  0 errors</span></div>
+    <div class="line"><span class="prompt">&nbsp;</span><span class="err">106/5819 frames show the WRONG picture</span></div>
+    <div class="line"><span class="prompt">$</span><span class="cmd">-c:v av1_cuvid   ->   -hwaccel cuda -c:v av1</span></div>
+    <div class="line"><span class="prompt">&nbsp;</span><span class="cmd">0 wrong frames  SSIM 1.000000</span><span class="fix">-> fixed</span></div>`;
+
 // ---------- read frontmatter ----------
 const postPath = join(ROOT, 'src', 'content', 'posts', `${slug}.md`);
 if (!existsSync(postPath)) {