fix(capture): growing file is MXF OP1a (DNxHR HQ) so Premiere can open it

The growing edit-while-record file was a fragmented MOV (empty moov), which
Premiere can't open ("Unable to open file on disk"). Write the growing master
as MXF OP1a / DNxHR HQ (Premiere-native, growable on disk); finalized master
keeps today's non-fragmented +faststart MOV.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/capture/src/capture-manager.js

@@ -155,12 +155,54 @@ const CONTAINER_EXT = {
   mov: 'mov', mp4: 'mp4', mkv: 'mkv', mxf: 'mxf', ts: 'ts',
 };
 
+// Growing-file (edit-while-record) master format.
+//
+// Premiere's "open capture in progress" / grow-on-disk support is FORMAT-
+// SPECIFIC. A fragmented MP4/MOV (`+frag_keyframe+empty_moov+default_base_moof`)
+// is NOT openable by Premiere as a growing file — its QuickTime importer needs
+// the classic stco/stsz/stts sample tables in a single top-level moov, which a
+// fragmented MOV never has while growing (samples live in moof/trun fragments).
+// Symptom: "Unable to open file on disk." (Confirmed via ffprobe on zampp2: the
+// growing .mov is ftyp + empty moov + repeating moof/mdat pairs, no sample
+// tables.)
+//
+// The robust, broadcast-standard growing format Premiere DOES ingest is
+// MXF OP1a (`-f mxf`) carrying a Premiere-native intra codec. We use DNxHR HQ
+// (4:2:2 8-bit) which ffmpeg's MXF muxer accepts (HEVC/ProRes-in-MXF are
+// rejected by this build), every frame is intra so a partially-written file is
+// decodable to its last complete frame, and MXF writes header + body partitions
+// incrementally so readers see valid essence mid-write. The same finalized .mxf
+// is also a clean, Premiere-native asset, so the promotion/finalized path stays
+// valid.
+//
+// Trade-off: DNxHR HQ is large (~22 GB/min at 1080p). Switch the profile to
+// dnxhr_sq below (~half the bitrate) if disk is the constraint.
+const GROWING_VIDEO_ARGS = [
+  '-c:v', 'dnxhd', '-profile:v', 'dnxhr_hq', '-pix_fmt', 'yuv422p',
+];
+const GROWING_EXT = 'mxf';
+
 function buildEncodeArgs({
   codec, videoBitrate, framerate,
   audioCodec, audioBitrate, audioChannels,
   container, isNetwork, isProxy = false,
   growing = false,
 }) {
+  // ── Growing master: force MXF OP1a + DNxHR, ignoring the configured MOV/
+  //    ProRes container/codec. This is the only combination Premiere opens as a
+  //    growing file (see GROWING_VIDEO_ARGS above). Audio is forced to PCM,
+  //    which MXF carries natively and Premiere ingests.
+  if (growing) {
+    const args = [];
+    if (isNetwork) args.push('-map', '0:v:0?', '-map', '0:a:0?');
+    args.push(...GROWING_VIDEO_ARGS);
+    if (framerate && framerate !== 'native') args.push('-r', framerate);
+    args.push('-c:a', 'pcm_s24le');
+    if (audioChannels) args.push('-ac', String(audioChannels));
+    args.push('-f', 'mxf');
+    return args;
+  }
+
   const v = VIDEO_CODECS[codec] || (isProxy ? VIDEO_CODECS.h264 : VIDEO_CODECS.prores_hq);
   const a = AUDIO_CODECS[audioCodec] || (isProxy ? AUDIO_CODECS.aac : AUDIO_CODECS.pcm_s24le);
   const fmt = CONTAINER_FMT[container] || (isProxy ? 'mp4' : 'mov');
@@ -180,19 +222,15 @@ function buildEncodeArgs({
   // moov-atom placement is the difference between a Premiere-openable master and
   // a "file cannot be opened" error.
   //
-  //  - Growing-file masters (edit-while-record on the SMB share) MUST be
+  // Finalized masters (the S3-piped recording that stops cleanly) must NOT be
-  //    fragmented so a moov/mvex is present from the first frame and the file is
+  // fragmented. Adobe Premiere's QuickTime/MOV importer reads the classic
-  //    decodable while still being written. The samples live in moof/trun boxes.
+  // stco/stsz/stts sample tables in a single top-level moov; a fragmented MOV
-  //
+  // (moof/trun, empty sample tables) makes Premiere report "file cannot be
-  //  - Finalized masters (the S3-piped recording that stops cleanly) must NOT be
+  // opened." We write a clean, non-fragmented MOV instead. `+faststart` puts the
-  //    fragmented. Adobe Premiere's QuickTime/MOV importer reads the classic
+  // moov before mdat on the second pass so the file is instantly
-  //    stco/stsz/stts sample tables in a single top-level moov; a fragmented MOV
+  // seekable/streamable too.
-  //    (moof/trun, empty sample tables) makes Premiere report "file cannot be
-  //    opened." We write a clean, non-fragmented MOV instead.
-  //    `+faststart` puts the moov before mdat on the second pass so the file is
-  //    instantly seekable/streamable too.
   if (fmt === 'mov' || fmt === 'mp4') {
-    args.push('-movflags', growing ? '+frag_keyframe+empty_moov+default_base_moof' : '+faststart');
+    args.push('-movflags', '+faststart');
   }
   // ProRes-in-MOV must carry a QuickTime brand or some importers reject the tag.
   args.push('-f', fmt);
@@ -384,8 +422,11 @@ class CaptureManager {
     if (growingActive && GROWING_SMB_MOUNT) {
       if (!mountGrowingShare()) growingActive = false;  // fall back to S3
     }
+    // Growing master is always MXF OP1a (the only Premiere-growable format here),
+    // regardless of the recorder's configured container — so it gets a .mxf
+    // extension, not hiresExt.
     const growingPath = growingActive
-      ? `${GROWING_PATH}/${projectId}/${clipName}.${hiresExt}`
+      ? `${GROWING_PATH}/${projectId}/${clipName}.${GROWING_EXT}`
       : null;
     if (growingPath) {
       try { mkdirSync(dirname(growingPath), { recursive: true }); }