DSH Sidebar Video Player

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A video player that lives in the right Sidebar of DeepSeek Harness (dsh), with live playback telemetry and a small, read-only MP4/MOV container reader.

Open it once and you can play a local video beside the conversation while reading its resolution, exact frame count, average frame rate, per-track bitrate, codec profile/level, buffer health and dropped frames — numbers a plain <video> element does not expose.

Install

GitHub source install (works without npm):

dsh plugin --profile web add github:XIANGDEEN/dsh-sidebar-video-player

For the desktop profile used by the DSH desktop app:

dsh plugin --profile desktop add github:XIANGDEEN/dsh-sidebar-video-player

If the package is later published to npm, the same profile can install it by name:

dsh plugin --profile web add dsh-sidebar-video-player

Restart or reload the Web UI after installing. The plugin appears as an enabled bundle row named dsh-sidebar-video-player.

Open it

• Right Sidebar → Start (the guide) → Video player.
• Or click the video icon beside Settings at the left Sidebar foot.

The player is a right-Sidebar tab. It needs an open Session, because the right column is session-scoped; the footer icon is disabled while no Session is on screen.

Features

• Play a local video by picker or drag-and-drop, or load an HTTP(S) video URL.
• Folder playlist: choose a folder and every video inside it is listed in a column to the right of the player. Each card shows a first-frame thumbnail and a duration badge; click an item to switch. The active item is highlighted, and the next item starts automatically when one ends.
• Sorting: order the playlist by name, duration, modified time or size, ascending or descending.
• Fullscreen: a header control and the existing transport button both toggle the player fullscreen; F does the same. Fullscreen hides the stats and playlist and keeps the transport controls.
• Playlist context menu: right-click a card for Rename, Copy file, Copy relative path, Delete local file and Refresh. File actions use the browser File System Access API and require choosing the folder through the directory picker with write access; the read-only folder-input fallback disables them.
• Custom transport: play/pause, seek, volume, mute, playback rate, picture-in-picture, fullscreen.
• Keyboard shortcuts while the player has focus: Space / K, J / L, arrow keys, M, F.
• Live playback telemetry:
  • current time, duration, progress, buffered range and buffer ahead;
  • measured decoded FPS from requestVideoFrameCallback;
  • presented frames, dropped frames and total video frames from getVideoPlaybackQuality();
  • playback rate and player state (playing, paused, buffering, ended).
• Deep MP4/MOV inspection without decoding media:
  • container: major/compatible brands, timescale, duration, moov position, fragmentation, track count;
  • video: codec fourcc, H.264/HEVC profile and level, coded/display size, aspect ratio, rotation, exact frame count, average FPS, per-track bitrate, bit depth, duration;
  • audio: codec, AAC profile, sample rate, channel count, bitrate, duration.
• Other browser-decodable containers (WebM, Ogg, …) still play and report measured resolution, FPS and frame counters. Container-level inspection is MP4/MOV only.
• A collapsible Raw probe data panel shows the exact parsed JSON.
• English and Simplified Chinese copy, using the host theme tokens.

How the MP4/MOV reader works

The reader never loads a whole file into memory. It walks top-level ISO-BMFF boxes with Blob.slice, reads moov once (capped at 64 MiB), and extracts:

• mvhd for the movie timescale/duration;
• each trak → tkhd (display size, rotation), mdhd (track timescale/duration, language), hdlr (video/audio handler), stsd (sample entry, codec fourcc, avcC/hvcC/av1C, esds), stts (sample count and timing) and stsz (sample bytes for the per-track bitrate).

It reports average values over the track, not instantaneous bitrate. Fragmented MP4 files are detected; when sample tables are empty, the player falls back to the measured metrics from the <video> element.

Compatibility

• Requires DSH >=0.2.1-rc.3 <0.3.0-0; built and tested against the Web client.
• Requires a browser that can decode the chosen container/codec. MP4/H.264/AAC is the safest choice; HEVC/AV1 support depends on the browser.
• The player is a view surface for playback and inspection. It registers no agent tool and writes no Session events. File writes use the browser File System Access API only after you choose a folder with write permission; the plugin does not request Host file-system authority.
• File operations (rename/copy/delete) require a Chromium-based browser or Electron and a folder chosen through the directory picker. The fallback <input webkitdirectory> path is read-only, so its context-menu file actions are disabled.

Permissions and privacy

• A selected local file is read through a browser Blob URL; it is not uploaded.
• Choosing a folder with write access lets the browser rename, copy or delete files in that folder when you pick a context-menu action. Nothing is written without an explicit action and the browser's permission prompt.
• A remote URL is fetched by the browser only for playback. The plugin does not proxy remote media or read remote container metadata.
• No analytics, telemetry, external service, or credentials are used.
• The only Host-side surface is the plugin bundle row; all player state stays in the Web page.

Verification

The MP4 reader was checked against ffprobe on two real files:

File	Resolution	Frames	Avg FPS	Video bitrate	Audio
boot.mp4	1280 × 720	193	24.000	2.50 Mbps	AAC LC, 32 kHz, stereo
background.mp4	1600 × 914	3766	30.000	0.68 Mbps	none

Those values match the ffprobe stream metadata for the same files. The plugin also passes module-factory, manifest/locale/patch, and registration contract checks in the source repository.

The file-operation helpers (copy naming, rename fallback, delete wiring and directory enumeration) are covered by tests. Actual permission prompts and filesystem writes require a Chromium/Electron environment and are not exercised by the automated suite.

No screenshot is declared. The player is a view surface; adding a staged screenshot that the code does not produce would be worse than an empty card. The numeric evidence above is reproducible from the reader.

Known limitations

• Deep container parsing covers .mp4, .m4v and .mov. Other formats are played but only expose what the browser reports.
• Remote video is not container-probed (cross-origin reads are not assumed).
• Encrypted sample entries (encv/enca) are not decrypted or inspected.
• The per-track bitrate is an average over the track, not a live network bitrate.
• The right Sidebar is session-scoped; there is no player without an open Session.
• File operations require Chromium/Electron and a folder chosen with write permission; the fallback folder input is read-only.
• Copy duplicates the file inside the same folder; it is not a system clipboard file copy.
• There is no "Reveal in Explorer" action; the browser sandbox does not expose the OS file manager.
• Delete and rename change the local file immediately after confirmation; there is no undo.

License

MIT. See LICENSE.