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Ubuntu 26.04 ships FFmpeg 8.0 (libavcodec 62); bump ffmpeg-next 7.1 -> 8.1 to bind it as the intended pairing. No source changes needed — the encode API surface we use (avcodec_send_frame, hwframe contexts, AV_PIX_FMT_CUDA, av_log) is stable across 7->8. Workspace builds + all tests green; clippy/fmt clean. Refresh the 7.x doc references. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>