PDA

View Full Version : Handbrake: The Bitrate Question?




roland.g
Feb 25, 2008, 12:31 PM
I have been encoding my DVDs in HB 0.9.2 and I started with the Apple TV preset that now has the AC3 Pass-through. I think it also has the AAC track, either way I have them both. I will really only play these on a TV via Apple TV, doubtful I will watch them on my Mac (though they look great full screen in iTunes) and I rip 500MB versions at 400bitrate for my iPhone on a 480x resolution. And while I have a Dolby Digital rec'r hooked up via optical to the Apple TV, I figured it was safer to encode the AAC incase I get a 2nd Apple TV unit at some point and the other TV needs the Pro-Logic stereo track.

I also switched to 2-pass encoding and turbo first pass (and then saved it as a new preset) and run most encodes on TS folders extracted with MTR so that I can process 3-4 overnight. The only other setting change I have made to the Apple TV preset is lowering the Bitrate from the default 2500 to 1500. I have done several tests and cannot see a difference between 1500, 2000, and 2500. The 1500 avg usually yields an avg bitrate of 1650-1950 anyway. Most are about 1775. On my 46" Samsung DLP 720p/1080i HDTV (set up as 720p on the Apple TV) the 1500 looks great. Down the line I can see this tv being replaced by a 53" at most. We don't really have room for anything bigger.

To me it makes sense to save the file size and go with the 1500. What are most people using. The 2500? 3000 or more? And why? Do you see a difference?



eddyg
Feb 25, 2008, 12:57 PM
I use CRF at 66%, which on some films without too much action yields about 1200kbps, and on action films at about 2500kpbs or upwards.

Just have to remember to not use it on old grainy films, and turn on weak denoising.

Note that to tell the difference in bitrate look at the moving pictures, not the static ones, the lower the bitrate the blurrier the movement will be, maybe even breaking up into blocks.

Cheers, Ed.

cohibadad
Feb 25, 2008, 01:06 PM
When I have compared 1500 to 2500 I can see a little more blurring if I look really close and compare side by side but I probably couldn't tell the difference otherwise. I will try eddyg's recommendation for crf if I decide to go for one encode for all devices.

roland.g
Feb 25, 2008, 01:09 PM
I use CRF at 66%, which on some films without too much action yields about 1200kbps, and on action films at about 2500kpbs or upwards.

Just have to remember to not use it on old grainy films, and turn on weak denoising.

Note that to tell the difference in bitrate look at the moving pictures, not the static ones, the lower the bitrate the blurrier the movement will be, maybe even breaking up into blocks.

Cheers, Ed.

You turn on weak denoising all the time or just for old grainy films?

And to tell the difference, do you mean in picture settings (can you tell the difference based on the setting in the front window) or do you rip a test chapter?

jbellanca
Feb 25, 2008, 01:32 PM
The 1500 avg usually yields an avg bitrate of 1650-1950 anyway. Most are about 1775.

Just wanted to clarify why you see higher bitrates than what you select. The bitrate you enter is for video only. The finished file is video + audio. So you're an average bitrate entered of 1500, plus the default 160 audio bitrate will put you at roughly 1660. Audio of 260 will put it at 1760.

As to you other questions, if you can't see a difference, great, go with what looks best to you. I generally use 1500 for "normal" movies, non-action, romantic comedies, etc. Then action flicks get 2000 if I like it but it's not a favorite. 2200 for ones I really like. 2500 for real favorites.

Where you'll really notice differences in low bitrates is really in panning shots, fast action, or large areas of almost the same color (the sky) - in all those cases, you'll likely see macroblocking.

Superman07
Feb 25, 2008, 01:55 PM
Has anybody done Casino Roayle? I used either 2000 or 2500, but in the pre-song chapter I noticed a lot of blotchy blooming if a light was in the scene. I'll try and check the timestamp when I get home. I'd appreciate if somebody could chime in with a comparsion. It's the same on two different displays, so I'm leaning towards an issue with the encode.

BuckWright
Feb 25, 2008, 02:19 PM
Other than potential degradation of image quality, what other effects result from lowering bitrate? Is the file size significantly smaller or does it take less time/computing power to encode?

On my 1st gen black macbook (2 gig of ram), it feels like encoding one movie is gonna break it. Temps average 185-190 while encoding.

NightStorm
Feb 25, 2008, 03:17 PM
Other than potential degradation of image quality, what other effects result from lowering bitrate? Is the file size significantly smaller or does it take less time/computing power to encode?

On my 1st gen black macbook (2 gig of ram), it feels like encoding one movie is gonna break it. Temps average 185-190 while encoding.

Changing the bitrate directly affects the size of the output file.