不要使用 null 调用 pc.addStream.相反，只是不要调用它.

Don't call pc.addStream with null. Instead, just don't call it.

• 当接收者也是回答者时，这就是全部.
• 当接收者是提供者时，您需要做一些额外的工作:

• When the receiver is also the answerer, this is all there is to it.
• When the receiver is the offerer, you need a little extra work:

您需要指定这些 RTCOfferOptions 到 createOffer代码>:

You need to specify these RTCOfferOptions to createOffer:

{ offerToReceiveVideo: true, offerToReceiveAudio: true }

原因是默认情况下，提供者只提供接收它正在发送的相同类型的流.我知道，这是一个愚蠢的默认值，但它给了报价者更多的控制权.从好的方面来说，始终指定这些选项并没有什么坏处，前提是它们符合您想要的行为.

The reason is that by default, the offerer only offers to receive the same kinds of streams it is sending. I know, a dumb default, but it gives the offerer a bit more control. On the upside, there's no harm in always specifying these options, if it matches your desired behavior.