How VLC to decide the packet is late?

[soho1001]

Hi All,

I got a big problem when I use VLC 2.1.0-rc2 to play live H.264 stream that is output by ffserver.
the stream format is rtp. it includes Audio+ video. One rtp stream is for Audio and another is for Video.
The payload type is 96 for Video, and 97 for Audio.
Video format: H.264, 1280x720, 30fps.
Audio format: PCM_S16_LE, 2 channel, 48000 sample rate.
I see the error when VLC debug message is enabled.
"avcodec error: more than 5 seconds of late video -> dropping frame (computer too slow ?)"
then the video stream is freeze.
But I can see the packet are received continually. Why all the packet are treated as "late packet" when the error message is output ?
It seems VLC use the time that the packet as received, but not the timestamp in rtp header, right?
Does any one have ideas?

[Jean-Baptiste Kempf]

It uses the packet pts to check.

[soho1001]

Hi,
Could you kindly help to explain the meaning of pts of packet?
Do you mean VLC use the timestamp in RTP header?
Does VLC use the difference between 2 timestamp of RTP pcaket?
if the difference is too large, then the second packet will be treated as late packet?
Could you kindly help to provide the hints?