Bitrate calculator confusion: ffmpegX calc vs VideoHelp calc

[Mildew]

Since I'm new to the whole DVD burning scene, please bear with me.

I don't understand why ffmpegX's bitrate calculator gives me much different values than VideoHelp's calculator [https://www.videohelp.com/calc.htm].

I have a 45 min 30 sec AVI file that I entered into both calculators. The VideoHelp calculator gives me a calculated/DVD max bitrate of 9570 kbits/sec for a 4.37 GB DVD.

ffmpegX's calculator (under the DVD mpeg2enc preset) suggests 4000 kbits/sec. I read elsewhere that 4500 kbits/sec is ideal. What's weirder is when I click "Best" in ffmpegX's calculator. It's "Best" recommended bitrate is 2994 kbits/sec.

I don't understand. Isn't that too low for a DVD? And why is it so different from VideoHelp's calculator? I don't know which bitrate I should select for encoding the DVD. Should I enter 4500 kbits/sec and leave it at that?

[Case]

DVD specs say you can't encode in a bitrate higher than 9800 kbps for all streams combined. That's about 9570 kbps max for your video. (Still, that would only fill ~75% of a DVD-R.) That's what the VideoHelp calculator gives you.

At 2994 kbps, ffmpegX will encode at what it believes to be 'good quality' for 720x480, NTSC film. ffmpegX's calculator takes it's own quality perception into the equation.

If you use 4500 kbps, you will find that for most scenes ffmpegX will use less, but that doesn't mean lower quality. It might be helpful for 'difficult' scenes with fire/water/filmgrain/video noise, i.e. where low bitrate encoders usually have trouble. But most viewers won't notice the difference.

[Mildew]

Thanks, Case.

[alph]

Just some extra comment

-Most calculators just take the duration of your video and fill the available space you say you have on your DVD. This gives very big number for short videos.

-4000kbits/s is a nice round number that will permit you to put a little over 2 hours of video on 1 DVD, and is pretty standard.

-The Best button in FFMPEGX give you a value based on the selected codec, video size, and framerate. Ex, 720x480 at 29,97fps for DVD mpeg2enc and DVD ffmpeg gives a rate of 3742kb/s. 2994 is for a framerate of 23.97

Major has said in the past, somewhere in this forum, that adding an extra 10% to the "best" numbers can help in some cases, but that going much beyond that adds little if anything in terms of quality. ffmpeg tends to disreguard extra bitrate, but mpeg2enc will tend to inflate file size if the bitrate is needlessly high.

Alph

[Mildew]

Just some extra comment

-The Best button in FFMPEGX give you a value based on the selected codec, video size, and framerate. Ex, 720x480 at 29,97fps for DVD mpeg2enc and DVD ffmpeg gives a rate of 3742kb/s. 2994 is for a framerate of 23.97

Major has said in the past, somewhere in this forum, that adding an extra 10% to the "best" numbers can help in some cases, but that going much beyond that adds little if anything in terms of quality. ffmpeg tends to disreguard extra bitrate, but mpeg2enc will tend to inflate file size if the bitrate is needlessly high.

Alph

Thanks, that's very helpful.