Convert 10-bit HEVC phone or camera footage to 8-bit H.264 with ffmpeg on Windows: why a plain…

Guide ID: art_01M7BSZVXA7C9PPAATZ2KA3915

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Guide title

Convert 10-bit HEVC phone or camera footage to 8-bit H.264 with ffmpeg on Windows: why a plain libx264 command still writes 10-bit High 10, and a script that forces 8-bit 4:2:0, refuses HDR and checks colour tags, frames and length

Coverage

For people with 10-bit HEVC footage who need a plain 8-bit H.264 MP4. A PowerShell script chooses the pixel format itself, stops on HDR footage and on a file that is already in the target form, then verifies the profile, colour tags, frame count, length and shown size and measures a luma PSNR. Tested on generated clips with ffmpeg 9.0.2 including nine refusals; nothing from a phone, no real HDR picture and no player.

Example

A 10-bit HEVC clip run through libx264 with no pixel format came out as H.264 High 10, still 10-bit; adding yuv420p gave High, 8-bit 4:2:0, and a plus sign before the format wrote an empty file and an error.

Useful starting points

• Say yuv420p without the plus sign, then look at the profile and pixel format of the file you got.
• Check that the colour tags before and after match; an HDR source stays HDR-tagged in 8 bits.
• A source that is already 8-bit H.264 needs no new encode.
• Open the result in your own player before you delete the original.