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Help me understand the quality slider

Oct 11, 2013 at 8:15 PM
My converted recordings are larger than I'd like. My confusion is that I don't understand how the quality slider relates to the slider in Handbrake for x264 that I'm more familiar with. They use an inverted logarithmic scale and the default is usually "RF:20".

I am using MKV Normal profile, with a minimum width of 1280. I am happy with the Handbrake equivalent of RF:20 - 22 but not sure how that relates to the percentage scale used in MCEBuddy.

Oct 11, 2013 at 8:28 PM
Quality slider increases the bitrate or quality parameter (-b or -qscale). As simple as that.

Marked as answer by rboy1 on 1/29/2014 at 9:13 AM
Oct 12, 2013 at 2:29 AM
So I guess what I'm asking is this: the qscale parameter is a number from 1-31. The quality slider is a scale from -95% to 100%. How do they correlate? Is -95% exactly 31, and 0% is 15, and 100% is 1?

Thank you!
Oct 12, 2013 at 4:23 AM
ah excellent question. I just reviewing the code and first I found a bug, changing the quality slider does not impact the qscale parameter, I've fixed that in the next BETA build for tonight, look out for it. (and thanks for asking this question, it helped me find the bug)

how it work simple, yes the scale is say from 31 (lowest) to 1 (highest) quality. (BTW this scale changes for each encoder and each codec types and MCEBuddy has inherent support for major codecs and encoders).

For each codec/encoder there is a default setup, e.g. for ffmpeg it's 3. The High is 31, Low is 1 and Current/Default is 3 (in reality the current is read from the profile at run time).

So if the quality increases (max increase allowed is 100%), the quality would from 3 to 1, say the increase is 50% the quality would go from 3 to 2 (half way between 3 and 1).
However on the reverse side, the range is 3 to 31, so a 50% reduction would take the quality from 3 to 17 (half way between 3 and 31).

Does that make sense?
Marked as answer by rboy1 on 1/29/2014 at 9:13 AM
Oct 12, 2013 at 4:23 AM
It's all relative to how the profile has been setup.
Oct 12, 2013 at 4:18 PM
Thanks, that's the info I was looking for. I can imagine for an app like this, it was difficulty to come up with a one-size-fits-all solution to quality adjustment. Now that you've explained it, it's much more clear what I need to do.

So if the profile settings had the ffmpeg default at 10 instead of 3, then the quality slider distribution would be different (i.e. 50% would be 5, and -50% would be 20)?
Oct 13, 2013 at 3:22 AM

Oct 13, 2013 at 3:26 PM
Thanks - of course, now I realize that the profile I'm using (MKV Normal) uses bitrate and not qscale!