From 5058afc980bae1388fe9ee7bab20a1131d7a57a3 Mon Sep 17 00:00:00 2001
From: William Valentin <william.valentin.info@gmail.com>
Date: Sun, 1 Feb 2026 15:58:11 -0800
Subject: [PATCH] feat: prefer derived mp4 playback with fallback

---
 apps/web/app/components/MediaPanel.tsx        | 40 ++++++++++++++++---
 apps/web/app/lib/playback.ts                  | 22 ++++++++++
 apps/web/src/__tests__/prefer-derived.test.ts | 18 +++++++++
 3 files changed, 75 insertions(+), 5 deletions(-)
 create mode 100644 apps/web/app/lib/playback.ts
 create mode 100644 apps/web/src/__tests__/prefer-derived.test.ts

diff --git a/apps/web/app/components/MediaPanel.tsx b/apps/web/app/components/MediaPanel.tsx
index da39362..29a4c98 100644
--- a/apps/web/app/components/MediaPanel.tsx
+++ b/apps/web/app/components/MediaPanel.tsx
@@ -24,6 +24,7 @@ type SignedUrlResponse = {
 };
 
 type PreviewUrlState = Record<string, string | undefined>;
+type VideoPlaybackVariant = { kind: "original" } | { kind: "video_mp4"; size: 720 };
 
 function startOfDayUtc(iso: string) {
   const d = new Date(iso);
@@ -45,7 +46,7 @@ export function MediaPanel(props: { selectedDayIso: string | null }) {
   const [viewer, setViewer] = useState<{
     asset: Asset;
     url: string;
-    variant: "original" | "thumb_med" | "poster";
+    variant: "original" | "thumb_med" | "poster" | "video_mp4";
   } | null>(null);
 
   const [viewerError, setViewerError] = useState<string | null>(null);
@@ -103,16 +104,35 @@ export function MediaPanel(props: { selectedDayIso: string | null }) {
 
   async function loadSignedUrl(
     assetId: string,
-    variant: "original" | "thumb_small" | "thumb_med" | "poster",
+    variant:
+      | "original"
+      | "thumb_small"
+      | "thumb_med"
+      | "poster"
+      | "video_mp4_720",
   ) {
-    const res = await fetch(`/api/assets/${assetId}/url?variant=${variant}`, {
-      cache: "no-store",
-    });
+    const url =
+      variant === "video_mp4_720"
+        ? `/api/assets/${assetId}/url?kind=video_mp4&size=720`
+        : `/api/assets/${assetId}/url?variant=${variant}`;
+    const res = await fetch(url, { cache: "no-store" });
     if (!res.ok) throw new Error(`presign_failed:${res.status}`);
     const json = (await res.json()) as SignedUrlResponse;
     return json.url;
   }
 
+  async function loadVideoPlaybackUrl(
+    assetId: string,
+  ): Promise<{ url: string; variant: VideoPlaybackVariant }> {
+    try {
+      const url = await loadSignedUrl(assetId, "video_mp4_720");
+      return { url, variant: { kind: "video_mp4", size: 720 } };
+    } catch {
+      const url = await loadSignedUrl(assetId, "original");
+      return { url, variant: { kind: "original" } };
+    }
+  }
+
   async function openViewer(asset: Asset) {
     if (asset.status === "failed") {
       setViewerError(`${asset.id}: ${asset.error_message ?? "asset_failed"}`);
@@ -123,6 +143,16 @@ export function MediaPanel(props: { selectedDayIso: string | null }) {
     setViewerError(null);
     setVideoFallback(null);
 
+    if (asset.media_type === "video") {
+      const playback = await loadVideoPlaybackUrl(asset.id);
+      const variantLabel =
+        playback.variant.kind === "video_mp4"
+          ? "video_mp4"
+          : playback.variant.kind;
+      setViewer({ asset, url: playback.url, variant: variantLabel });
+      return;
+    }
+
     const variant: "original" | "thumb_med" | "poster" = "original";
     const url = await loadSignedUrl(asset.id, variant);
     setViewer({ asset, url, variant });
diff --git a/apps/web/app/lib/playback.ts b/apps/web/app/lib/playback.ts
new file mode 100644
index 0000000..2a9d812
--- /dev/null
+++ b/apps/web/app/lib/playback.ts
@@ -0,0 +1,22 @@
+type Variant = {
+  kind: "video_mp4";
+  size: number;
+  key: string;
+};
+
+type PlaybackInput = {
+  originalMimeType: string | null | undefined;
+  variants: Variant[];
+};
+
+export function pickVideoPlaybackVariant(input: PlaybackInput):
+  | { kind: "video_mp4"; size: number }
+  | { kind: "original" } {
+  const mp4Variant = input.variants.find(
+    (variant) => variant.kind === "video_mp4" && variant.size === 720,
+  );
+  if (mp4Variant) {
+    return { kind: "video_mp4", size: mp4Variant.size };
+  }
+  return { kind: "original" };
+}
diff --git a/apps/web/src/__tests__/prefer-derived.test.ts b/apps/web/src/__tests__/prefer-derived.test.ts
new file mode 100644
index 0000000..42df1ac
--- /dev/null
+++ b/apps/web/src/__tests__/prefer-derived.test.ts
@@ -0,0 +1,18 @@
+import { test, expect } from "bun:test";
+import { pickVideoPlaybackVariant } from "../../app/lib/playback";
+
+test("prefer mp4 derived over original", () => {
+  const picked = pickVideoPlaybackVariant({
+    originalMimeType: "video/x-matroska",
+    variants: [{ kind: "video_mp4", size: 720, key: "derived/video/a.mp4" }],
+  });
+  expect(picked).toEqual({ kind: "video_mp4", size: 720 });
+});
+
+test("falls back to original when no derived", () => {
+  const picked = pickVideoPlaybackVariant({
+    originalMimeType: "video/x-matroska",
+    variants: [],
+  });
+  expect(picked).toEqual({ kind: "original" });
+});