ffmpeg.c what are pts and dts ? what does this code block do in ffmpeg.c?

Question

• In simple terms what are pts and dts values?
• Why are they important while transcoding [decode-encode] videos ?

What does this code bit do in ff

Answer 1

B frames are predicted from I and P frames. B frames usually have more errors compared to I and P and hence are not recommended for prediction, though they might be closer in time. There are algorithms in which B is used for prediction but it is from a past B frame and not future B frames.

So in a sequence of I P B1 B2, Decode order is I P B1 B2 and Display order is I B1 B2 P. P is predicted from I, B1 from both I and P, B2 again from I and P.