ffmpeg libx264 is noisy

After converting video with ffmpeg to H264, my video is noisy.

ffmpeg -i http://192.168.1.10:5530/bysid/106 -map 0:v:0 -map 0:a:0 -c:v libx264 -c:a mp2 out.mkv

Normal:

Noisy subtitle:

Same result with tag preset ultrafast, slow.
Same result with GPU transcode.

Answer

Attribution
Source : Link , Question Author : mohsen nayyeri , Answer Author : Community