> The fTimestampBase
> is set as the random value, so there is no possibility to have similar
> timestamps in both subessions.

That is totally correct.  Different media streams have different RTP timestamps 
(perhaps with different timestamp frequencies, as is the case here), and the 
mapping from RTP timestamp to presentation time is done via RTCP packets, and 
is done automatically by our code.

Users of the “LIVE555 Streaming Media” software should ***never*** have to 
concern themselves with RTP timestamps.  Our software automatically converts 
presentation times to RTP timestamps (at the sender) and RTP timestamps to 
presentation times (at the receiver), using the data from RTCP “SR” packets - 
again automatically.

See http://live555.com/liveMedia/faq.html#separate-rtp-streams

So, the *only* think you need to concern yourself with is the ‘presentation 
time’ of each frame of media (audio or video).  If these are correct, and 
aligned with ‘wall clock’ time (i.e., the time that you’d get by calling 
“gettimeofday()”), then the 'presentation time’s - as seen by the receiver - 
will also be correct, and your media *will* be synchronized.  (Note, however, 
that the first few presentation times - as seen by the receiver - might not be 
synchronized.  For an explanation of this, see
        http://live555.com/liveMedia/faq.html#rtcp-synchronization-issue
)

If you are not getting proper audio/video synchronization at your receiver 
(e.g., VLC), then you ***must not*** be setting the presentation times 
correctly.


> As far as I understand, there is also a need to have the same
> fTimestampFrequency values

Absolutely not.  The RTP specification allows different substreams (even with 
synchronized) to have different RTP timestamp frequencies.


> but the audio has 44100 sampling frequency and video has this value hardcoded 
> to 90000.

This is correct.  The RTP payload format standards (for AAC audio and H.264 
video, respectively) mandate this.  But again, you never need to concern 
yourself with RTP timestamps or RTP timestamp frequencies.  Our software takes 
care of this automatically.


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


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