x-video-to-vertical-social-cut

name	X Video to Vertical Social Cut
description	Turn an X/Twitter video or local source clip into a verified 9:16 social export using the proven direct FFmpeg/run-command media path: preserve widescreen foreground, dark blurred background, burned-in captions, and no persistent header by default.

X Video to Vertical Social Cut

This is a production runbook, not a generic video-editing checklist. Use it when Raul supplies an X/Twitter video URL or a local MP4 and asks for a short vertical captioned social cut.

Non-negotiable execution lane

The footage stays in the direct FFmpeg/run-command media lane from ingest through export.

• Resolve/download the real source MP4.
• Inspect the actual source and transcript, choose the moment manually.
• Generate ASS captions from the selected source range.
• Build the 9:16 frame with a direct FFmpeg filter: full landscape foreground over a dark blurred source-derived background.
• Burn captions and mux the trimmed original audio in that same FFmpeg render.
• Decode, probe, and visually inspect the final MP4 before delivery.

Never use HyperFrames, HTML Motion, Remotion, Creative compositions, or frame-by-frame browser rendering to crop, caption, carry, or export the source footage. Those are only optional overlay/design tools when Raul specifically asks for designed graphics on top of an already-rendered direct-FFmpeg cut.

Read before executing

Read references/proven-direct-ffmpeg-runbook.md. It contains:

• Windows FFmpeg/FFprobe resolution commands;
• the exact working filter_complex_script for the Odyssey no-header export;
• a real ASS caption style and mobile-safe placement;
• direct PowerShell export/probe/decode/frame-QA commands;
• failure recovery for X media, cloud transcription, paths, and captions.

Do not invent a new rendering lane when this reference has the known-good commands.

Output contract

Default output is a mobile-ready 1080×1920, 30fps H.264/AAC MP4 with +faststart:

• Full widescreen source video stays centered and visible. Never crop away useful UI, cinematic action, or end-card copy merely to fill 9:16.
• Unused vertical area is a softened/darkened blurred copy of the original footage.
• Captions are big, high contrast, phrase-length, and placed in the lower safe area.
• There is no persistent title, hook, source credit, tag, watermark, or header unless Raul explicitly requests it.
• Use the requested duration; otherwise choose one coherent 20–45-second moment with a clear opening line.

Exact production workflow

1. Resolve source. For an X URL, use the X/media resolver. If X extraction does not expose media metadata, use the downloader/resolver fallback and continue with the downloaded MP4. Do not abandon the edit and do not change render lanes.
2. Probe and inspect. Use the runbook FFprobe command. Generate/reuse a cached transcript, make a contact sheet or frame samples, then choose the exact START and DURATION manually.
3. Write captions. Make an .ass file whose timing starts at 00:00 for the selected clip. Use the runbook baseline style: Arial 62, white, black outline, lower-safe MarginV=175, no title/tag events.
4. Render. Put the runbook’s canonical source-video filter into a text file. It trims video/audio, creates the blurred 1080×1920 background, centers the uncropped foreground, applies ASS captions, and maps trimmed original audio. Run the direct FFmpeg export command.
5. QA the actual MP4. Full decode, stream/dimension probe, early-middle-ending frame exports, then visual review. Repair by changing only the source time range, captions, or FFmpeg filter. Never swap to HTML rendering.
6. Deliver only after passing QA. State real duration, dimensions, codecs, and visible QA findings. Mention any genuine uncertainty rather than claiming an audio/listening verdict without evidence.

Verified reference: Heavy Pulp Odyssey, no header

The proven no-header Odyssey export used this exact construction:

[0:v]trim=duration=30,setpts=PTS-STARTPTS,split=2[bgsrc][fgsrc];
[bgsrc]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,boxblur=25:10,eq=brightness=-0.18:saturation=0.72[bg];
[fgsrc]scale=1080:-2:force_original_aspect_ratio=decrease[fg];
[bg][fg]overlay=(W-w)/2:(H-h)/2,ass='CAPTION_PATH'[v]

It produced a 30-second 1080×1920 H.264/AAC MP4 with the full cinematic landscape frame, dark blurred background, bold outlined all-caps captions, no added header, no black frames, no crop loss, and no caption clipping after actual-export visual QA.

Required QA gates

Do not deliver unless all are true:

• FFmpeg full decode exits successfully.
• FFprobe reports 9:16 output, H.264 video, and AAC audio.
• Early, middle, and ending output frames have been checked visually.
• Captions are readable and clear of mobile UI.
• No black/corrupt frame, aggressive foreground crop, or accidental header is present.
• The visual verdict is based on the exported MP4, not only the source, timeline, or a generic metadata scorer.

Avoid

• Do not reopen the generic Creative/HyperFrames path for normal source footage.
• Do not leave a permanent title strip because an old Kimi template had one.
• Do not let a missing X video hint or cloud STT quota abort the workflow.
• Do not claim a clip is good based only on a technical probe.