What is the difference between CBR, VBR 1 pass and VBR 2 pass?

Started Mar 20, 2017 | Questions
DMKAlex
DMKAlex Veteran Member • Posts: 6,484
What is the difference between CBR, VBR 1 pass and VBR 2 pass?
1

Can someone explain this please?

Thanks.

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Vesku Senior Member • Posts: 2,964
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?
2

DMKAlex wrote:

Can someone explain this please?

Thanks.

CBR = constant bitrate

VBR = variable bitrate (more bitrate when lots of sharp motion, less with static scene)

2 pass =  First pass anylyses how much bitrate needed and second pass renders the video. Needs twice the time to render.

DMKAlex
OP DMKAlex Veteran Member • Posts: 6,484
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?
1

Vesku wrote:

DMKAlex wrote:

Can someone explain this please?

Thanks.

CBR = constant bitrate

VBR = variable bitrate (more bitrate when lots of sharp motion, less with static scene)

2 pass = First pass anylyses how much bitrate needed and second pass renders the video. Needs twice the time to render.

Since 2 pass requires twice the time to render, is there any distinct benefit over 1 pass?

And what benefit that VBR over CBR, or vice versa?

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Vesku Senior Member • Posts: 2,964
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?
2

DMKAlex wrote:

Vesku wrote:

DMKAlex wrote:

Can someone explain this please?

Thanks.

CBR = constant bitrate

VBR = variable bitrate (more bitrate when lots of sharp motion, less with static scene)

2 pass = First pass anylyses how much bitrate needed and second pass renders the video. Needs twice the time to render.

Since 2 pass requires twice the time to render, is there any distinct benefit over 1 pass?

And what benefit that VBR over CBR, or vice versa?

2 pass optimizes bitrate so it makes smaller file with about the same quality as 1 pass.

VBR makes also smaller file than CBR because it uses only the bitrate it needs. Static scenes uses very low bitrate with VBR but CBR uses max all the time.

DMKAlex
OP DMKAlex Veteran Member • Posts: 6,484
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?
1

Vesku wrote:

DMKAlex wrote:

Vesku wrote:

DMKAlex wrote:

Can someone explain this please?

Thanks.

CBR = constant bitrate

VBR = variable bitrate (more bitrate when lots of sharp motion, less with static scene)

2 pass = First pass anylyses how much bitrate needed and second pass renders the video. Needs twice the time to render.

Since 2 pass requires twice the time to render, is there any distinct benefit over 1 pass?

And what benefit that VBR over CBR, or vice versa?

2 pass optimizes bitrate so it makes smaller file with about the same quality as 1 pass.

VBR makes also smaller file than CBR because it uses only the bitrate it needs. Static scenes uses very low bitrate with VBR but CBR uses max all the time.

Thank you very much. I think I am going to stick with the 1 or 2 pass VBR then.

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Osman Vielma New Member • Posts: 1
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?
2

I tried all 3 options (VBR 2 pass, 1 pass, and CBR) all, more or less, took the same time (5 minutes to recode a long video) and got the, more or less, the same file size (18 MB), the only difference was, VBR 2 pass was definitively better quality. And the second pass, I think, was faster than the first one.

🙂👍

Sean Nelson
Sean Nelson Forum Pro • Posts: 15,944
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?

Osman Vielma wrote:

I tried all 3 options (VBR 2 pass, 1 pass, and CBR) all, more or less, took the same time (5 minutes to recode a long video) and got the, more or less, the same file size (18 MB), the only difference was, VBR 2 pass was definitively better quality. And the second pass, I think, was faster than the first one.

If your footage was relatively static then you wouldn't expect very much difference between them.  You're more likely to see differences if the footage contains a lot of motion, especially if it's a lot of random motion like the whole frame filled with leaves rustling in the wind or reflections on undulating water.  Or if it contains a lot of cuts to difference scenes.

sludge21017
sludge21017 Veteran Member • Posts: 3,746
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?

CBR probably wasn't turned up high enough.

Entropy512 Veteran Member • Posts: 5,977
Re: What is the difference between CBR, VBR 1 pass and VBR 2 pass?

Osman Vielma wrote:

I tried all 3 options (VBR 2 pass, 1 pass, and CBR) all, more or less, took the same time (5 minutes to recode a long video) and got the, more or less, the same file size (18 MB), the only difference was, VBR 2 pass was definitively better quality. And the second pass, I think, was faster than the first one.

🙂👍

In general, the main use case for VBR 2 pass is where you have a very strict limit on file size (such as "must fit on a DVD") and want to get the maximum possible quality for that specific file size.

Otherwise, constant rate factor (one particular method of VBR rate control, there are multiple) is usually best as far as size/quality tradeoffs.  However it's not always a good idea if the goal is streaming, because it allows significant bitrate spikes.  Other rate control schemes don't offer quite as good of a quality vs. rate tradeoff, but avoid large spikes in rate that can be problematic for a stream and some hardware decoders.

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