Firefox PLI Requests in "Play from Disk" Example

[AfonsoVilalonga]

Hello,

I was testing the Pion "play from disk" example with Firefox while monitoring the network traffic using Wireshark and observed an interesting behavior. At the start of the connection, Firefox consistently sends 5 PLI requests.

I then investigated this further using the WebRTC Encoded Streams API. It appears, at least to me (though I could be mistaken), that Firefox does not initially receive a key frame but rather some delta frames, which might be causing this issue.

I am unsure whether this behavior is induced by Firefox or Pion; however, I thought it was interesting to share.

Is this a commonly known behavior? Or am I missing something?

Thank you,
Afonso Vilalonga

[nils-ohlmeier]

Even though it's a little too late, but maybe still useful if someone looks at this in the future:

Yes it is pretty normal for the receiver to send PLI's right after the connection gets established (and it should not be specific to Firefox). It basically depends on the exact timing. If the sender sends the initial frames too soon/early for the receiver, then the receiver fail decoding just the P-frames. Thus it needs a new I-frame to be able to start decoding.