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Originally Posted by sirt
But I want to know ! It's possible I am not able to understand without any specifical knownedge ; so, according to you, there is no need to set that in so far as the quantizer will AUTOMATICALLY choose the adequate quantizers and lowering the values could restrict its work, am I right this time ? You will say I am asking too much but let's try again...how can you be sure the "right" quantizer will be chosen ? And what do you mean by "right" ?
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The "right" quantizers are that which will hit desired average(!) bitrate you have selected.
If you want to know which quantizers happened to be the "right" ones for a particular source and for a particular target bitrate, just take the final output file and throw it at some analyze tool which can show the qunatizers
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I am also confused with the I-Frames and B-Frames chosen during an encode...how is that possible the encoder will choose the right one as a reference ? From what I have read it is possible to set manually what will be a I-Frame or B-Frame trough an override text but it is probably dedicated to XviD or x264 gurus. Of course I won't assume to tell you if a good frame was used a reference by the encoder to reconstruct other frames around basing its work on that refrenced one but...what if this reference frame is one of the worse from the video such as a ringed or destroyed one ? Then I think the segment near that frame will be encoded with a bad quality and I couldn't control that.
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As explained earlier, scenecut detection is used to detect scene boundaries. If a scenecut is detected, a key-frame (I-Frame in the case of Xvid, IDR-Frame in the case of x264) will be placed at this point.
Deciding whether a particular frame "in the middle of a scene" should be coded as a P-Frame or as a B-Frame is a complex task and requires pretty complex algorithms/heuristics.
If you want to know how x264's adaptive B-frame decision algorithm works (actually there are two), you will have to study the source code. Many more simple encoders use a
fixed number of consecutive B-Frames...