How to calculate bitrate for 1080p encode

lchiu7 · 2nd May 2009, 05:33

Up till now I have been encoding my BluRay rips as 720P. But thinking down the line I might upgrade to a 1080p set thought I might start encoding as 1080P instead. But using the bitrate calculator in Megui gives the same bitrate for 720p and 1080p and from what I have seen if I use the rate given for 720p for 1080p encode, the outputs shows obvious macroblocking, especially in darker scenes.

I guess I could take the value given by the bitrate calculator and scale it up 50%. I am not shooting for a specific target size the content resides on my server - just want something that works for 1080p and looks good.

Any other methods that could be used?

Thanks

Kurtnoise · 2nd May 2009, 06:41

Quote:

Originally Posted by lchiu7

I am not shooting for a specific target size the content resides on my server

why you need to calculate the bitrate then ?

lchiu7 · 2nd May 2009, 07:47

Quote:

Originally Posted by Kurtnoise

why you need to calculate the bitrate then ?

Well I do want to save space but also not have too many artifacts like macroblocking. So I am just adding about 40% to the value calculated by the bitrate calculator. Not scientific and will see how it goes.

poisondeathray · 2nd May 2009, 15:22

Why don't you use crf mode then ? It's faster to encode (1pass), and should give you the same average quality that you set, but the filesize may vary greatly between titles. A slow drama movie generally requires less bitrate to look the same "quality" than a fast paced action movie with explosions. If you arbitrarily pick a bitrate, it might be too little for some movies, or too high for others depending on the source material

(But if this is targetted for a device, then VBV isn't optimal unless you use 2pass encoding)

lchiu7 · 2nd May 2009, 21:23

Did a quick look on the documentation for CRF and it isn't clear how to set it. All I can see is that it should be between 18-26 which seems like a large range. Is there a some method for making a more precise setting?

Agree that if I have constant bitrate I might too much or too little so while space isn't an issue, I don't want to have not enough of a bitrate and see macroblocking. And wildly varying spaces between titles isn't an issue also - so long as it's not the same as the source(!) when I might has well copy the entire contents of the disc (BD or HD-DVD) to the server and just remove the extraneous tracks (other languages, subtitles, etc.)
BTW this is targeted for a device - the Popcorn Hour.

Who Am I ? · 2nd May 2009, 21:41

might be offtopic but would'nt cqm's help with the bitrate distribution on scene's / regions ( mostly dark ones ) on which u're worried about ?

movmasty · 3rd May 2009, 22:00

Quote:

Originally Posted by lchiu7

Did a quick look on the documentation for CRF and it isn't clear how to set it. All I can see is that it should be between 18-26 which seems like a large range. Is there a some method for making a more precise setting?

Yes: testing....

range 21-24 is ok for you?

2nd May 2009, 05:33	#1 \| Link
lchiu7 Registered User Join Date: Apr 2002 Posts: 279	How to calculate bitrate for 1080p encode Up till now I have been encoding my BluRay rips as 720P. But thinking down the line I might upgrade to a 1080p set thought I might start encoding as 1080P instead. But using the bitrate calculator in Megui gives the same bitrate for 720p and 1080p and from what I have seen if I use the rate given for 720p for 1080p encode, the outputs shows obvious macroblocking, especially in darker scenes. I guess I could take the value given by the bitrate calculator and scale it up 50%. I am not shooting for a specific target size the content resides on my server - just want something that works for 1080p and looks good. Any other methods that could be used? Thanks Last edited by lchiu7; 2nd May 2009 at 05:39.

2nd May 2009, 15:22	#4 \| Link
poisondeathray Registered User Join Date: Sep 2007 Posts: 5,377	Why don't you use crf mode then ? It's faster to encode (1pass), and should give you the same average quality that you set, but the filesize may vary greatly between titles. A slow drama movie generally requires less bitrate to look the same "quality" than a fast paced action movie with explosions. If you arbitrarily pick a bitrate, it might be too little for some movies, or too high for others depending on the source material (But if this is targetted for a device, then VBV isn't optimal unless you use 2pass encoding) Last edited by poisondeathray; 2nd May 2009 at 15:25.

2nd May 2009, 21:23	#5 \| Link
lchiu7 Registered User Join Date: Apr 2002 Posts: 279	Did a quick look on the documentation for CRF and it isn't clear how to set it. All I can see is that it should be between 18-26 which seems like a large range. Is there a some method for making a more precise setting? Agree that if I have constant bitrate I might too much or too little so while space isn't an issue, I don't want to have not enough of a bitrate and see macroblocking. And wildly varying spaces between titles isn't an issue also - so long as it's not the same as the source(!) when I might has well copy the entire contents of the disc (BD or HD-DVD) to the server and just remove the extraneous tracks (other languages, subtitles, etc.) BTW this is targeted for a device - the Popcorn Hour.

2nd May 2009, 21:41	#6 \| Link
Who Am I ? x264 Fanatic ! Join Date: Mar 2009 Location: Earth I guess ? Posts: 36	might be offtopic but would'nt cqm's help with the bitrate distribution on scene's / regions ( mostly dark ones ) on which u're worried about ?