When watching IPTV program, a video display appears. What are the possible causes? (Multiple Choice)

When watching IPTV program, a video display appears. What are the possible causes? (Multiple Choice)
A . Lost some key frames during program compression;
B . Some key frames were lost during line transmission;
C . Speed limit was imposed on the equipment;
D . The port activation rate on the MODEM is too small

Answer: ABCD