From what data is the graph plotted in the panel buffer? Which formats are supported?

The Buffer panel displays the results of the analysis (for AVC and HEVC video formats only). For unsupported video formats, nothing is displayed in this panel. The buffer parameters are based on the Buffering_period, Pic_timing SEI values and HRD parameters from Sequence_parameter_set header. If SEI or HRD data is not available, the parameters are reconstructed using the stream level\tier for HEVC. If SEI values or HRD parameters for an AVC file are absent, the graph will not be constructed.