[Live-devel] Timestamp gap in RTCP Report for MPEG1or2VideoStreamFramer

[Ross Finlayson]

>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>sending REPORT
>fTimestampBase: 0xae0daf0d, tv: 683383.099932, RTP timestamp: 101919
>Creating RTCP SR packet, SSRC is 0x6da5, NTP is : tv: 683383.099932, 
>TimeStamp is: 101919
>sending RTCP packet
>  80c80006 00006da5 83b4ebf7 199524c0 00018e1f 000000db 0003c76d 
>81ca0005 00006da5 010a7377 6f70742d 766f6970 00000000
>schedule(1.015347->683384.121916)
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.201906, RTP timestamp: 21097
>fTimestampBase: 0xae0daf0d, tv: 683382.235273, RTP timestamp: 24100
>fTimestampBase: 0xae0daf0d, tv: 683382.235273, RTP timestamp: 24100
>
>Obviously the TimeStamp value of the RTCP SR packet should be 
>between 21097 and 24100.

No - because the 'NTP' time (683383.099932) that's used for the RTCP 
SR packet is not between 683382.201906 and 683382.235273.  The RTP 
timestamp of 101919 corresponds to the time 683383.099932.

It's perfectly OK for the NTP time that's used in a RTCP "SR" report 
to differ from the presentation time used in RTP packets that bracket 
it.  However, because the RTCP SR 'NTP' time is computed using 
"gettimeofday()" (i.e., 'wall clock' time), the presentation times 
for your media samples (that get passed to RTP) *must* also be 
aligned with 'wall clock' time.

The timestamp generation code (for both RTP and RTCP) is correct. 
However, for it to work correctly, you must feed it correct 
presentation times.
-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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