BD-Rebuilder : questions about options ?

[Nico8583]

Hi,
I have 3 questions about BD-Rebuilder :
- I've seen open-gop is not enabled by default on BD-Rebuilder (and x264) but it seems to be needed in Blu ray specifications. What is the best choice ? A Blu ray player must be compliant so open-gop should be supported by all Blu ray players ? Is it the same rule for AVCHD ?
- What is the "Apply Dynamic Range Compression" about audio ? Is it for 5.1 AC3 or only for 2.0 AC3 ?
- Is "Strict AVCHD" override all others encoding options or is it only for remux ?
Thank you !

[jdobbs]

1. You are incorrect in your statement. Open GOPs are NOT "needed in the Blu Ray specifications". It is optionally supported but isn't "needed". If you want to use open GOPs you just add OPEN_GOP=1 to your INI file. I made closed GOPs the default for a reason -- but it's been so long ago that I can't remember why and can't find it in my notes. I suspect it was because of issues on some players (especially software players). There are a lot of tweaks I've done over the years to accommodate the largest majority of players. They should support certain things -- but that doesn't mean they actually do (b-pyramid is another example).

2. "Apply Dynamic Range Compression" fixes the common Dynamic Range over-compensation that many BD's use in trying to be cool (making background and music so loud as to drown our things like common voice and sounds). If you find that over-compensation annoying (like many do) you can fix it with this option. Dynamic Range is one of those things that is a two edged sword.

3. Strict AVCHD ensures BD-5/9 output will play on all players that support AVCHD. It does several things, not just related to muxing. For example, many people like to keep DTS audio on their BD-5/9 discs, and many players will support it. But DTS is not a part of the AVCHD standard -- so strict AVCHD forces it to be reencoded. So it doesn't "override all other encoding options" -- but it does override some.

[Nico8583]

Thank you ! I believed OpenGOPs were necessary but I was wrong...
A last question : I've tried to make a MKV (Movie only, CRF 23) and I've seen the command line used to encode. I'm curious to know why do you use "--slow-firstpass" and "--stats FILE.STATS" with CRF ?

[jdobbs]

It's possible to do a second pass after a CRF. So I added those to make that possible. Example: When doing a predicted CRF, it is possible that it could be oversized -- so by having the stats files available, BD-RB will automatically do a second pass (using bitrate) to make it fit.

[Sharc]

Thank you ! I believed OpenGOPs were necessary but I was wrong...
A last question : I've tried to make a MKV (Movie only, CRF 23) and I've seen the command line used to encode. I'm curious to know why do you use "--slow-firstpass" and "--stats FILE.STATS" with CRF ?
- In case you are unhappy with the resulting file size from your CRF encode you could run a 2nd pass based on the .stats file from the initial CRF pass.
- BD RB can also initiate a 2nd pass automatically in case of an oversize in CRF prediction mode (targeting a certain files size).

BD RB is pretty smart, eh? :cool:

Edit:
Ooops, jdobbs was faster.....

[jdobbs]

Barely... it looks like we posted within the same minute!

[Nico8583]

Thank you, I didn't know it was possible :)
Is there any impact on encoding speed with or without these parameters ?

[jdobbs]

Thank you, I didn't know it was possible :)
Is there any impact on encoding speed with or without these parameters ?No (at least not with a CRF encode). I guess there may be a slight decrease with the writing time of the stats file -- but it would be very, very insignificant.

[Nico8583]

Thank you, so I let default settings. I'm going to try CRF 23 / MKV / DD 5.1 640 in order to see if quality is sufficient for 1080p :)