b-pyramid: is there a quality change?

[kartola]

Hi,
i encoded a 1080 50p video with x264.
Using Ripbot it set by default b-pyramid=none.
If i re-encode the movie with b-pyramid=normal i'm going to obtain some increase or decrease of quality?
I know that b-pyramid give more compression (not so much) but what about quality?

Thanks

[shon3i]

more compression=more efficiency=more quality, simple like that

[kartola]

I don't know. It depends by the way it compress.
More compression=detail losses?

[shon3i]

I don't know. It depends by the way it compress.
More compression=detail losses?
no that means, some frames can be compressed more without visual quality loss, and leave bits to other frames that need more to look equally good.

[kartola]

Yes i understand what you mean.
But using a constant crf? Someone tested some difference changing b-pyramid setting?

[IanB]

In crf mode the change will be in final file size, i.e a more efficient representation, the "quality" should be the same, i.e as specified by the crf value.

In 2 pass mode the file size is the constant, the "quality" is the variable.

[Asmodian]

But do not assume the quality is the same between two encodes at the same crf but one with b-pyramid on and one with it off. So just running, for example, two crf 23 encodes, one with b-pyramid on and one with it off, and comparing the sizes doesn't work.

The way I would test this (still not perfect) would be to run two two-pass encodes targeting the same bit-rate. One using --tune ssim & --ssim and b-pyramid=none, one using --tune ssim & --ssim and b-pyramid=normal.

It would be even better to do two two-pass encodes to a fairly low bit-rate, so you can easily tell differences in quality, one with b-pyramid on and one with it off and compare the quality visually. I find this method tricky because I don't trust myself but it is probably the "most real" method.