Re: [FFmpeg-user] gain the highest quality with H264 at a certain bit rate

negin tebyani wrote:

this is the source video mediainfo:

That's not ffmpeg console output, but anyway ..

Bit rate mode : Constant Bit rate : 4 000 Kbps

So it's not a much of a master but (I guess) some re-encoded web stream made from a broadcast stream, which you are encoding for a third time. Was the "good" sample coded from this? Maybe whoever made that one had a better master. In this case, I guess the original broadcast, which was likely higher and variable bitrate.

and yes, I need to use constant bitrate. do I need to use 2 pass with constant bitrate?

Probably not - others may/have given their opinion. AIUI 2 pass is better for variable bitrate when targeting some file size.