https://chatgpt.com/share/67a4b87c-a0fc-8007-b4c9-887145620c6b
Below are two example ffmpeg command lines—one using libx265 (CPU-based, software encode) and one using NVIDIA’s NVENC-based AV1 encoder—that meet your criteria. I’ve kept the original 708×480 resolution (with DAR 4:3) and used CRF/CQ settings in the visually lossless–to–near-lossless range (CRF around 18 for x265; and for AV1 NVENC we use a comparable constant‐quality “CQ” value).
This command uses libx265 with a “slow” preset and CRF set to 18 (feel free to adjust between 18 and 20 if you’d like a tiny bit more compression versus quality). It also forces the pixel format to yuv420p (8‑bit) to match the source’s 8‑bit depth. (Since your source has a nonstandard resolution with a display aspect ratio of 4:3, ffmpeg should preserve the metadata—but if you ever need to enforce it you can add a video filter like -vf "setdar=4/3"
.)