"Best" tab for bitrate

[danielmak]

I'm wondering about the use of the "Best" tab in the Video section. Is this tool useful for improving quality or am I better off leaving the settings that ffmpeg detects when I drag a file into the program?

Using an example I am converting an MP4 file to DVD using DVDmpeg2enc. When I dragged the file into ffmpeg the bitrate appeared as 4000 kbit/s. When I hit the Best button the bitrate jumped to 4491 kbit/s. Sometimes ffmpeg lowers the bitrate when I hit Best and sometimes it raises the bitrate. In past instances I have switched the rate back to 4000 (why, I can't say--just trusting the original encoders I guess). Obviously the Best button is there for a reason. Do folks who've used the program for a long time use this button? Why/why not? Thanks.

[Case]

4000 is default
3742 is 'Best' for NTSC (29.97 fps) @ 720x480
3746 is 'Best' for PAL (25 fps) @ 720x576
2994 is 'Best' for NTSC Film (23.976 fps) @ 720x480

If 4491 kbps is 'Best' for your clip, then you must have entered strange settings; video size most likely.

[danielmak]

If 4491 kbps is 'Best' for your clip, then you must have entered strange settings; video size most likely.

I dragged an avi file in that originated in Australia. The settings are Video Size 720 X 576, Autosize DVD, and PAL. I changed Video Size to 720 X 480, Autosize to DVD 16:9, and PAL to NTSC Film. I didn't change anything else in Audio or Tools. I checked No SVCD scan, Decode with Quicktime (the Mplayer setting hasn't worked for me and it takes a long long time), set 3:2, Altivec, and Bicubic (so the only addition was the 3:2). So the 4491 was the setting that came up.

I just did it again and the setting is 2994. So there must have been some kind of glitch. Thanks for providing some sense of the best settings.

[broaddd]

I know this is a bit old, but my follow-up question is similar: how does ffmpegx determine the 'best' bitrate.

For example, it suggests about 750kbps for 720x304 x.264 conversions; yet on the Handbrake forum most people suggest 1500 or even 2000+ kbps for x.264 archives of DVDs in high quality.

If you do use Handbrake and set the constant quality rate to say 70% (the same as ffmpegx' Qmin settings I think), you do end up with files that obviously use a much higher bitrate than 750kbps.

Personally, I can't see much difference once you go past 1500, or even 1000, but I was curious as to how ffmpegx determines the 'best' bitrate for that resolution on that encoder is 750ish...

Broad