Quality prediction with the big3 prior to encoding

[iparout]

Hi.

I'm taking my first steps down the DVD Backup road and I am following the newest big3 guide (http://www.doom9.org/mpg/scenaid.htm)here at the site.

What I would like to know is if there's any way to get a good estimation of the final quality of the movie, before encoding it with CCE. Something like the compressibility check which is used in GordianKnot. Such a thing would really be useful, cause I don't want to spend 6 hours doing a 4-pass VBR encoding with CCE just to find out that the quality is aweful...

I searched the forums and found that there's the infamous Q-Factor, which has to be under 9 in order for the quality to be considered acceptable, however I didn;t find any step-by-step guide for noobs like me in order to find out the Q-Factor of the movie.

Can anyone tell me how to find the Q-Factor before starting the CCE encoding ?

Are there any other ways to predict quality apart from the Q-Factor ?

Thanks in advance.

[seewen]

http://forum.doom9.org/showthread.php?s=&threadid=74141

[iparout]

Originally posted by seewen
http://forum.doom9.org/showthread.php?s=&threadid=74141

Well, I read that thread and as far as I can understand, it doesn't do what I asked. What this thread tries to achieve is to predict the filesize of the output file when a specific Q-Value is given. I want quite the opposite ; find out the Q-Factor of the output video when a specific bitrate is given (without encoding the whole movie of course).

[Trahald]

what i do is run doitfast4u.. take the .avs file of the main movie and edit in the line SelectRangeEvey(2400,12).. this is a .5% sample.. i check the output with bitrate viewer and that will give me an idea of the q-value.. you can also watch the values cce gives as it encodes.

what seewen suggested can be used to fit your needs with a little tweaking

there are no plans to add this to big3 since , for example, with divx/xvid you have the option of adding disks and/or small changes in resolution. with dvd you are basically stuck with 1 disk and large changes in resolution (352x576 is too much for a main feature) a change to 704x576 can be a small help but not enough of one to add a hard coded feature..

for the few that are willing to tweak.. (myself on occasion) doing it by hand is pretty painless.

[seewen]

Originally posted by iparout
Well, I read that thread and as far as I can understand, it doesn't do what I asked. What this thread tries to achieve is to predict the filesize of the output file when a specific Q-Value is given. I want quite the opposite ; find out the Q-Factor of the output video when a specific bitrate is given (without encoding the whole movie of course).



I don't understand your problem:

1) Launch the OPV on sample with Q.Factor of 60, 40, 30, 20, etc.. (1st you use only 1 Qfactor. And if needed, you raise/down the QFactor depending of the result, till the derived bitrate=target bitrate )

2) At the end, compare the derived bitrate of the sample(s) to your main movie target bitrate.
If target bitrate = 3500, and Derived bitrate of OPV sample QFactor 26 = 3478, it's obvious that the target bitrate will produce a QFactor ~26

[iparout]

Originally posted by seewen
I don't understand your problem:

1) Launch the OPV on sample with Q.Factor of 60, 40, 30, 20, etc.. (1st you use only 1 Qfactor. And if needed, you raise/down the QFactor depending of the result, till the derived bitrate=target bitrate )

2) At the end, compare the derived bitrate of the sample(s) to your main movie target bitrate.
If target bitrate = 3500, and Derived bitrate of OPV sample QFactor 26 = 3478, it's obvious that the target bitrate will produce a QFactor ~26

Well, looks like we are talking about different Q. You are talking about Q60, Q40 e.t.c and I'm talking about the Q factor, which takes values smaller than 9 (at least if you want your encodings to have good quality). Or at least that's what I understood by browsing and reading the forums for the last couple weeks (link here (http://forum.doom9.org/showthread.php?s=&threadid=74893&perpage=20&highlight=Qvalue&pagenumber=2) )... I, by no means, consider myself as an expert though, so I may be wrong.