Only set this value if you know none of the individual stream durations and also do not set any of them.
仅在以下情况下设置该值:你不知道任何一个单流持续时间,而且你也没有设置任何这些值.
This is deduced from the AVStream values if not set.
如未设置,该值从AVStream值推算.
Only set this value if you know none of the individual stream durations and also do not set any of them.
仅在以下情况下设置该值:你不知道任何一个单流持续时间,而且你也没有设置任何这些值.
This is deduced from the AVStream values if not set.
如未设置,该值从AVStream值推算.