AutoMKV x264 Encoding final size is not what i request [Archive]

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MalickT

23rd March 2009, 20:45

Hi. Im encoding a x264 video using Constant Quality profile and i set the output file to be 8GB (Disk Settings input is set to 8000). The original is 16GB. Is ok if there is some quality loss but the output file is not 8GB, its always larger like around 9.5GB. Im use no resize filters and original width resolution allso no audio track. Why the output is not the size i request?

J_Darnley

23rd March 2009, 20:48

You cannot use crf (or qp) rate-control mode(s) and know the final file size. If you want to get a specific file size you will need to set the correct bitrate to reach it. You can use crf as the first pass but on the second you must set the bitrate you want.

MalickT

23rd March 2009, 20:58

How can i do that? A little quide please...

im a new at using AutoMKV. I use version 0.91. Im interested in getting the maximum quality as possbile, it does not matter that it takes longer to encode, but i want to maintain the original resolution

Chengbin

24th March 2009, 01:46

You should update your AutoMKV to 0.98.4 here

http://forum.doom9.org/showthread.php?t=140178

Choose 2_pass_xxx profile (anything above balanced) and set the bitrate.

MalickT

24th March 2009, 08:51

but i want the maximum quality as possible. I have read that Constant Quality profile gives me that.

How do i know to set the right bitrate?

24th March 2009, 10:11

but i want the maximum quality as possible. I have read that Constant Quality profile gives me that.
In the first post you said that you want to limit the output to 8 GBs. That also limits the quality. With the 2-pass mode you get maximal quality while keeping the output size within a certain limit.

How do i know to set the right bitrate?
I don't know if AutoMKV includes a bitrate calculator. If not, you can calculate it yourself or use the tool in MeGUI, for example.

Calculating the bitrate (from MEncoder documentation (http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-dvd-mpeg4.html#menc-feat-dvd-mpeg4-2pass)):
If you aim at a certain size, you will have to somehow calculate the bitrate. But before that, you need to know how much space you should reserve for the audio track(s), so you should rip those first. You can compute the bitrate with the following equation: bitrate = (target_size_in_Mbytes - sound_size_in_Mbytes) * 1024 * 1024 / length_in_secs * 8 / 1000 For instance, to squeeze a two-hour movie onto a 702MB CD, with 60MB of audio track, the video bitrate will have to be: (702 - 60) * 1024 * 1024 / (120*60) * 8 / 1000 = 740kbps

MalickT

24th March 2009, 10:45

I ment maximum quality on terms of reducing the fail to 8GB. (I know qulity will reduce compared to original) So if I just use 2-pass mode and set the size final to 8GB I get exacly 8GB and i dont have to calculate the bitrate myself?

Im using AutoMKV version091

Chengbin

24th March 2009, 14:17