CRF Question

Beak · 12th August 2012, 17:26

I have just installed a Bluray burner in my machine.

I have a 36 Gig m2ts file that has to shrink to 23 total.

I am hoping someone could suggest a CRF number that will get me around 20 gigs plus/minus.

I am hoping to avoid the time 2 pass encoding take as I have a fair number of filters slowing me down.

Any help would be appreciated.

Sharc · 12th August 2012, 18:03

As you can read from many posts in this forum it is pointless to expect a certain file size by selecting a certain CRF - not even approximate. For a given CRF the file size depends on the complexity of the pictures (motion, details, noise, your filters, etc) and will accordingly vary significantly.
If you want a certain size you need to go for 2-pass.

sneaker_ger · 12th August 2012, 23:28

or 1 pass ABR

Beak · 13th August 2012, 17:30

The bitrate calculator has made a CRF estimate that seems OK. I realize it will miss the target size if the movie is complex but its working well so far,

I'll try ABR at a bitrate of 20900. That should hit the filesize and seems to be a good enough bitrate to ensure good quality.

Thanks to those who helped.

Groucho2004 · 13th August 2012, 17:36

Quote:

Originally Posted by Beak

I'll try ABR at a bitrate of 20900.

Don't.

Also, the time you need to figure out the correct CRF value for your target size is probably longer than a good old 2 pass encode.

blubb444 · 18th August 2012, 02:38

If you're really using an extremely slow script (for example QTGMC at "placebo" on a 1080i source) then you might consider to first encode your script to lossless (for example --preset fast --qp 0, you can of course use faster presets too) and then run a 2-pass on that file.

12th August 2012, 17:26	#1 \| Link
Beak Registered User Join Date: Jun 2003 Posts: 127	CRF Question I have just installed a Bluray burner in my machine. I have a 36 Gig m2ts file that has to shrink to 23 total. I am hoping someone could suggest a CRF number that will get me around 20 gigs plus/minus. I am hoping to avoid the time 2 pass encoding take as I have a fair number of filters slowing me down. Any help would be appreciated.

12th August 2012, 18:03	#2 \| Link
Sharc Registered User Join Date: May 2006 Posts: 3,964	As you can read from many posts in this forum it is pointless to expect a certain file size by selecting a certain CRF - not even approximate. For a given CRF the file size depends on the complexity of the pictures (motion, details, noise, your filters, etc) and will accordingly vary significantly. If you want a certain size you need to go for 2-pass. Last edited by Sharc; 12th August 2012 at 18:05.

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12th August 2012, 23:28	#3 \| Link
sneaker_ger Registered User Join Date: Dec 2002 Posts: 5,565	or 1 pass ABR

13th August 2012, 17:30	#4 \| Link
Beak Registered User Join Date: Jun 2003 Posts: 127	The bitrate calculator has made a CRF estimate that seems OK. I realize it will miss the target size if the movie is complex but its working well so far, I'll try ABR at a bitrate of 20900. That should hit the filesize and seems to be a good enough bitrate to ensure good quality. Thanks to those who helped.

18th August 2012, 02:38	#6 \| Link
blubb444 Registered User Join Date: Mar 2012 Posts: 40	If you're really using an extremely slow script (for example QTGMC at "placebo" on a 1080i source) then you might consider to first encode your script to lossless (for example --preset fast --qp 0, you can of course use faster presets too) and then run a 2-pass on that file.