3 reference frames or 1 reference frame+1 b frame

[qyqgpower]

I use Nero Recode 2 to encode AVC video for PSP, so I want to ask this question.Which option will produce higher quality?
I usually use 267kbps for 320*240 or 368*208 @29.97fps.

[Sharktooth]

3 reference frames + 3 b-frames...

[qyqgpower]

PSP won't play 3 ref + anymore b-frame clip since it only supports main@level3.
and 2.6 firmware have some problems with 2 ref+some b-frames so I would ask the quastion.

[Sharktooth]

then 1 ref + 1 b-frame

[qyqgpower]

thank you for the reply.
and can you explain why 1 ref + 1 b-frame would be better than 3 refs? thanks!

[bond]

thank you for the reply.
and can you explain why 1 ref + 1 b-frame would be better than 3 refs? thanks!it will not be better ;)
its just that when the psp doesnt support more, you have no choice (unless you stop using the psp for that)

[charleski]

PSP won't play 3 ref + anymore b-frame clip since it only supports main@level3.
and 2.6 firmware have some problems with 2 ref+some b-frames so I would ask the quastion.Just for reference: MainProfile@Level3 should support 3 reference + 3 b-frames +pyramid.
The PSP, of course, is a different matter.

I just mentioned this because Level 3 is a standard target for StdDef encodes.

[Randall]

B frames are good. Some hardware and software cannot handle too many of them though. Just a little FYI about I, P, and B frames if you want to know. B frames require less bits for encoding, and therefor you can get a better quality encode with more of them at the same bitrate.

Intra pictures (or slices)
* Is a picture coded without reference to any picture except itself.
* May be generated by an encoder to create a random access point (to allow a decoder to start decoding properly from scratch at that picture location).
* May also be generated when differentiating image details prohibit generation of effective P or B frames.
* Typically require more bits to encode than other picture types.

Often, I pictures are used for random access and are used as references for the decoding of other pictures. Intra refresh periods of a half-second are common on such applications as digital TV broadcast and DVD storage. Longer refresh periods may be used in some environments. For example, in videoconferencing systems it is common to very seldom send I pictures.

Predicted pictures (or slices)
* Require the prior decoding of some other picture(s) in order to be decoded.
* May contain both image data and motion vector displacements and combinations of the two.
* Can reference previous pictures in decoding order.
* In older standard designs (such as MPEG-2), use only one previously-decoded picture as a reference during decoding, and require that picture to also precede the P picture in display order.
* In H.264, can use multiple previously-decoded pictures as references during decoding, and can have any arbitrary display-order relationship relative to the picture(s) used for its prediction.
* Typically require fewer bits for encoding than I pictures do.

Bi-predictive pictures (or slices)
* Require the prior decoding of some other picture(s) in order to be decoded.
* May contain both image data and motion vector displacements and combinations of the two.
* Include some prediction modes that form a prediction of a motion region (e.g., a macroblock or a smaller area) by averaging the predictions obtained using two different previously-decoded reference regions.
* In older standard designs (such as MPEG-2), B pictures are never used as references for the prediction of other pictures. As a result, a lower quality encoding (resulting in the use of fewer bits than would otherwise be used) can be used for such B pictures because the loss of detail will not harm the prediction quality for subsequent picture.
* In H.264, may or may not be used as references for the decoding of other pictures (at the discretion of the encoder).
* In older standard designs (such as MPEG-2), use exactly two previously-decoded pictures as references during decoding, and require one of those pictures to precede the B picture in display order and the other one to follow it.
* In H.264, can use one, two, or more than two previously-decoded pictures as references during decoding, and can have any arbitrary display-order relationship relative to the picture(s) used for its prediction.
* Typically require fewer bits for encoding than either I or P pictures do.

[foxyshadis]

DeathTheSheep found that on animation with a low bitrate or low framerate (8-12 fps), reference frames are more important than b-frames, but on other types of video b-frames help more than extra references. So that's the one exception. (And even then it's not a big difference unless you're able to add lots of references.)