Advice needed on bitrates for BD backups

[gav1577]

Hi just a quick question i am archiving my blurays on to BD5 and BD9 i am confused about bitrate limits for a BD5
and BD9 i have a movie that's 140mins long to fit on a dvd5 the bitrate would have to be 4002kbps and 7800kbps for a BD9 is 4002kbps too low for a BD5 ? to achieve very good quality might it be better to encode my movie to 1280x720 and fit on a dvd9 or would 7800kbps be ok for 1920x1080? basically is there a rule of thumb for minimum bitrate for BD5 1280x720 & BD9 1920x1080? thanks :)

[Blue_MiSfit]

Bitrate is impossible to predict. Some 1080p content might look fantastic at 8mbit, some might look quite bad.

I've seen 3mbit 1080p that was surprisingly good, and I've seen some that was unwatchable.

That being said, I think _most_ of the time ~8mbit should be enough. It's very hard to say. Sounds like 2pass for sure, and I would definitely suggest some filtering to reduce noise. Psy-RDO should help too..

Maybe you can do a 2pass encode of a small scene where there's a lot of action. See how it looks, and if it's not good enough, go down to 720p.

Heck, compare the source, and lanczosresize(1280,720).spline16resize(1920,1080). A lot of times, the difference is exceedingly minor.

~MiSfit

[gav1577]

thanks for the advice will have to do some tests with small clips like you suggested :)

[gav1577]

One more thing should bframe mode be left as auto or none i was told in the past to keep grain and transparency it was good to set it to --direct none is this still the case with the latest builds of x264 this part has always confused me :confused:Thanks

[Ranguvar]

Almost positive --direct auto is the way to go for 2-pass (enable in both passes), and --direct spatial for 1-pass.

[gav1577]

Thanks Ranguvar :thanks:

[Dark Shikari]

Direct none is generally dumb; it means skip analysis is never done, so loads of bits are just completely wasted on residual-less blocks that would otherwise be skips, but have to be coded anyways even though they have no residual data.

[gav1577]

Direct none is generally dumb; it means skip analysis is never done, so loads of bits are just completely wasted on residual-less blocks that would otherwise be skips, but have to be coded anyways even though they have no residual data.

Thanks for the info Dark Shikari

[nixo]

Almost positive --direct auto is the way to go for 2-pass (enable in both passes), and --direct spatial for 1-pass.

How would I go about this if I were to use CRF in pass 1?
Would --direct auto be ok in this case as I'm not actually using the output, or should I just use --direct spatial in both passes?

[Dark Shikari]

How would I go about this if I were to use CRF in pass 1?
Would --direct auto be ok in this case as I'm not actually using the output, or should I just use --direct spatial in both passes?Doesn't change anything--you can still use auto in both passes.

[nixo]

Cool. Thank You.