Hi Rob.
> Improving compression efficiency is mostly equivalent to improving > quality at a particular bit rate. > > I-frames are completely coded. P-/B-frames are predicted from other > frames. That is, the frame data contains information to reconstruct > motion vectors that point to positions in previous (or future in some > cases) frames and the difference between this prediction and what > should actually be seen. The pixel data from these reference frames is > combined with the difference to produce the desired result. It's not > really guessing, rather minimising the difference between the > prediction and the source. > > Using predicted frames (P-/B-frames) improves compression efficiency > (and so quality at a particular bit rate) significantly because there > is a lot of temporal redundancy in video. Frames are similar to > previous/future frames in close proximity temporally. Predicting a > frame from those in close proximity temporally allows for more > information per bit, which is what compression efficiency is really. > That's how most video codecs work. > Thanks for the detailed explanation. So if higher compression (achieved by increasing the GOP), helps to improve the quality under preset bitrate, it possible to retain better quality under same GOP, by simply increasing the bit-rate - correct?. Regards. _______________________________________________ libav-user mailing list [email protected] https://lists.mplayerhq.hu/mailman/listinfo/libav-user
