[FFmpeg-devel] NVENC regression in newer FFmpeg builds; CPU encoding works correctly and fixes MPEG artifacts

[FFmpeg-devel] NVENC regression in newer FFmpeg builds; CPU encoding works correctly and fixes MPEG artifacts

[Sheikh Afnan via ffmpeg-devel]

Hello FFmpeg Team,

I would like to report observations comparing older FFmpeg builds with
newer releases (latest from gyan), specifically regarding NVENC support and
MPEG handling.

Behavior with older FFmpeg builds:

- NVENC (h264_nvenc) works correctly on NVIDIA GTX 1660 Super and RTX 3050
systems.
- Using explicit colorspace and range settings (BT.709, limited/TV range)
produces correct colors.
- However, when processing MPG/MPEG files, visible horizontal line
artifacts (interlacing/combing on faces) appear, even though these
artifacts are not present in the original source files.

Behavior with newer FFmpeg builds (latest gyan):

- CPU-based encoding (libx264, CRF 25) produces correct output:
   - Colors appear correct without forcing colorspace parameters.
   - MPG/MPEG files no longer show the face-line/interlacing artifacts seen
in older builds.
- NVENC, however, does not function correctly:
   - NVENC is unavailable or fails to initialize on systems where it
previously worked.
   - This affects both NVIDIA GTX 1660 Super (driver 12.4) and RTX 3050
systems (driver 12.x).
   - As a result, applications are forced to use CPU encoding in newer
builds.

In summary:

- Newer FFmpeg builds improve CPU-side decoding and MPEG handling.
- NVENC support that worked reliably in older builds appears to regress or
become incompatible in newer builds for the same hardware and driver
environments.

I would appreciate clarification on:

- Whether there have been intentional changes or increased requirements for
NVENC initialization in FFmpeg 6.x.
- Any recommended steps to restore NVENC functionality on supported GTX and
RTX GPUs.
- Whether this NVENC behavior is expected or considered a regression
compared to older builds.

Thank you for your continued work on FFmpeg. Any guidance would be greatly
appreciated.

Best regards,
Sheikh Afnan
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