How to determine bitrate for a BD to AVC/H.264 rip?

[JimmyBarnes]

Is there any objective ("mechanical") way to do this?

As opposed to the empirical approach of simply guessing at a certain bitrate, doing the encode then checking certain key sequences for acceptability?

[Guest]

To the extent that it is not determined by the constraints of your target playback hardware, it is purely subjective.

(I'm surprised that someone with 400+ posts would ask something like this.)

[BigDid]

Hi,

Another approach is to focus on Cq (constant quality) rather than bitrate. An example given by Atak for Avatar is CRF 22 as good basis for comparison (see his screenshot in that thread).
Anything with lower CRF will be better to extremely good (to not use the word best ).

I wanted to be able to burn my encode of Avatar to a 2 layers DVD so I used CRF 23 for 1920/1080 which resulted in an average bitrate of around 6500Kbp/s (not at home so recalling) with latest x264 rev (1583 from recalling).

Purist(s) may object that viewing that encode on a 50" or 60" screen will not be visually transparent compared to the original; I don't have one so I am happy with what I have :)

Did

PS: told you to stay in the newbie section to avoid remarks... ;)

[JimmyBarnes]

To the extent that it is not determined by the constraints of your target playback hardware, it is purely subjective.

(I'm surprised that someone with 400+ posts would ask something like this.)

Almost all of those 400 to do with DVD ripping, not BD ripping which is quite new to me

[Guest]

What was the objective mechanical method you developed for DVDs?

[JimmyBarnes]

Hi,
PS: told you to stay in the newbie section to avoid remarks... ;)

I reasoned that only the dummies like me would inhabit that forum (can the blind lead the blind?), so I came here knowing I would find wisdom and guru/demigods in the topic

[JimmyBarnes]

What was the objective mechanical method you developed for DVDs?

As far as bitrate goes, to use quantizer = 2.00 as a reference size. Then a 2-pass encode targeting 80 % of that size always gave me a satisfactory/good encode. If the q=2 size was small enough (say 2CDs or so) I would accept that without further effort.

And yes I did watch each encode carefully throughout subsequently

[creamyhorror]

As far as bitrate goes, to use quantizer = 2.00 as a reference size. Then a 2-pass encode targeting 80 % of that size always gave me a satisfactory/good encode. If the q=2 size was small enough (say 2CDs or so) I would accept that without further effort.
For quality-based encoding, the equivalent for x264 is CRF (constant rate factor) mode. You simply choose a CRF value that gives you good results and acceptable bitrate on a few sources, and stick with that (with possible adjustments for particularly difficult/complex sources like old grainy movies).

The range of usual CRF values is 17-23, the lower resulting in exponentially higher bitrates.

[JimmyBarnes]

For quality-based encoding, the equivalent for x264 is CRF (constant rate factor) mode. You simply choose a CRF value that gives you good results and acceptable bitrate on a few sources, and stick with that (with possible adjustments for particularly difficult/complex sources like old grainy movies).

The range of usual CRF values is 17-23, the lower resulting in exponentially higher bitrates.

Hooray, the info I have been seeking for the past few weeks expressed in a way I can understand...

What's your e-mail address so I can send you a PayPal donation? (ha, ha, just kidding) :)

I suppose you use RipBot for transcoding BD to H264? (sadly RB disables FLV playback on my PC, something which I cannot have happen). If you happen to use other packages, do you have a good guide for?

Muchos gracias

[creamyhorror]

Hooray, the info I have been seeking for the past few weeks expressed in a way I can understand...
Glad to hear.

I suppose you use RipBot for transcoding BD to H264? (sadly RB disables FLV playback on my PC, something which I cannot have happen). If you happen to use other packages, do you have a good guide for?
I don't transcode BDs, but Ripbot and Handbrake are the two I hear mentioned. There are a few possibilities in the MPEG-4 Encoder GUI forum, you could go check them out.

Note that when you transcode to HD resolutions, you can generally use a higher ratefactor than if transcoding to SD. So for BDs you'd probably stay in the 20-23 range.