Bitrate Encoding VBR vs CBR?

[Killertom63]

Should I use VBR or CBR if I'm rendering at 17Mbps? I understand the differences, etc. File sizes are not an issue either.

Thanks.

[Ann Bens]

I like vbr2 as it analyzed before encoding. Gives a slightly better picture.

[excited_Genie16B8]

My preference is for VBR 1 pass.  It offers a size advantage over CBR and doesn't unnecessarily add to export times.

[Killertom63]

I don't mind the size difference, nor export times really as they're like 5/10 minutes.

My issue is I feel like more can go wrong with VBR, as it has to constantly change the bitrate. I rather it get the full bandwidth per frame, to maximise quality.

The only reason why I'm asking this is because I had a video that had a bad, bad encoding glitch and it made the footage unviewable. And I'm starting to wonder if that is because of how VBR works, because the footage would only break when something new would happen on screen, etc. 

[excited_Genie16B8]

My issue is I feel like more can go wrong with VBR, as it has to constantly change the bitrate. I rather it get the full bandwidth per frame, to maximise quality.

I think that's an unfounded concern.  If a frame only needs 10 bits, why use 20?

Certainly there's nothing wrong with CBR.  But the overwhelming majority of video you watch is VBR.

[Killertom63]

But say for example doesn't an iPhone use a VBR style of recording. While a Red camera uses a CBR style of recording? In the sense of iPhone want to get the best file sizes for you, while Red want the best quality? So if that's the case there, why wouldn't it be the case in post?

[Stan Jones]

I am a member of facebook, but even when I log in, it is a closed group so I can't see the content.

Killertom63  wrote

doesn't an iPhone use a VBR style of recording.

Many devices and cameras use VBR. The settings, and they are important, are often in terms of the max bitrate. The problematic format you're probably thinking of for phones (iphones and others) and many other devices is VFR (variable frame rate), which Premiere does not handle.

[Killertom63]

No, I'm not talking about VFR, I hate VFR. It's a lazy mans tool who can't have processing power. Haha. Anyway thank you all for the help, it was more of a discussion more than anything. Cheers.

[excited_Genie16B8]

why wouldn't it be the case in post?

You're vastly oversimplifying there.  RED cameras shoot RAW, most pro/consumer cameras shoot H.264.  You can't compare those two.

The reason you don't generally want to deliver CBR is because most deliverables do have space limitations.  VBR is more efficient while offering the same quality at similar bitrates.

[yairb999]

Some people think CBR gives better results than VBR.
See here:

https://www.facebook.com/groups/adobepremierepro/permalink/1524466490948298/?comment_id=152446967428...

[excited_Genie16B8]

I'm not a member of Facebook.

But you can always run your own tests with your material.  My guess is that you'll find little quality difference, only a size difference.

[yairb999 · Accepted solution]

OK then, here is that post on facebook by Kyle Koch:

VBR (variable bitrate) is used successfully on commercial DVDs but the engineers pay very close attention to increase the bitrate for complex visuals.

It can be used to reduce your file size, but personally, I find it delivers poor results.

From our tests, we’ve seen digital blockiness @ 10 and 15Mbps for fast motion.

20Mbps CBR is the first level that gave us solid results. You could go higher for uploads to social media but may not need to.

For videos that don’t change the pixels much, like a static shot of a person talking with a plain BG, you can go much lower on the bitrate.

Our vids are cut fast and with lots of motion so we tend to upload ProRes422 and 20Mbps h264.

For in-term client previews (like raw interviews) we will post as low as 8Mbps.

[Killertom63]

This is some good info! Thank you!

[yairb999]

So I've now checked with Kyle Koch if he still recommends CBR 20 Mbps over VBR and his response was:

No. I tend to go with 2-pass VBR but keep a constant bit rate (setting both numbers the same). If I need quality, 20Mbps for 2K and 40Mbps for 4K.

For real quality, I use ProRes422HQ tho.

[R Neil Haugen]

From my experience, if you've got significant and continuous motion going on, CBR may be a benefit. IF the viewer will be watching on a good quality large (relative to viewing distance) screen that is quite properly setup.

Broadcast stuff, really.

If your material is going out to folks watching via YouTube/Vimeo/browsers on the web in office computers and on their phones wherever they may be ... it is very doubtful there will be a difference the viewer can see.

So ... if you're prepping for b-cast, yea, go with CBR.

If you're prepping for basic web ... probably it is of no help.

And of course, your mileage will vary. Test.

Neil