[Live-devel] Request to Fix inconsistent timestamps in openrtsp

[Robert Krakora]

Hello,

I use VLC 0.9.10 and receive audio and video streams on a large scale LAN
both unicast and multicast from a variety of security and webcams via VLC
with live555 RTSP and video and audio are in sync with the
hasBeenSynchronizedUsingRTCP() function getting called.  Which version of
VLC are you using?  Ross is correct, this appears to be a VLC issue and not
a live555 issue.

Best Regards,

-- 
Rob Krakora
Senior Software Engineer
MessageNet Systems
101 East Carmel Dr. Suite 105
Carmel, IN 46032
(317)566-1677 Ext. 206
(317)663-0808 Fax

On Mon, Jan 18, 2010 at 9:18 PM, Ross Finlayson <finlayson at live555.com>wrote:

> The problem I experience with VLC is that it takes the first set of
>> presentation stamps as it's seed.
>>
>
> VLC's "live555" demux module (see "modules_demux_live555.cpp") does not do
> this.  (At least, it shouldn't be doing this.  If - after inspecting that
> code - you're *sure* there's a bug there, then please report it to VLC (not
> to us; VLC is not our software).)  Note, in particular, the call to
> "hasBeenSynchronizedUsingRTCP()" in that code.  So, if you're not using the
> "live555" demux module, then you probably should.  Once again, please don't
> try to reinvent the wheel.
>
>
>
>  I have tried playing with the code myself in vlc but have not had success
>> getting a proper result out of it, it's beyond my ability to resolve.
>>
>
> Once again, are you using VLC's "live555" demux module?  If not, why not?
>  (In any case, alleged bugs in VLC are off-topic for this mailing list.)
>
>
>  Could openRTSP
>>
>
> I think you mean "the LIVE555 Streaming Media libraries", not "openRTSP".
>  "openRTSP" is a demo application, not a library.
>
>
>   not simply calculate an offset after the RCTP packet and adjust each
>> subsequent packet by that offset to keep the whole PTS stream consistent?
>>
>
> Because - in the case where you have more than one substream (e.g., audio +
> video), that would *not* keep their presentation times in sync.
>
> Remember, once again, that the presentation times for the audio and video
> streams - after "hasBeenSynchronizedUsingRTCP()" returns True for both -
> will be accurate, and in sync with each other.  But the presentation times
> that occurred *before* "hasBeenSynchronizedUsingRTCP()" returns True will
> not be in sync. Therefore, although we could - in principle - add an offset
> to the audio presentation times so that their presentation times after RTCP
> sync are consistent with those before RTCP sync, we could not also do the
> same for the video presentation times, without bringing the audio and video
> presentation times out of sync with each other.
>
> This is why only the presentation times that occur after
> "hasBeenSynchronizedUsingRTCP()" returns True can be trusted for A/V
> synchronization, and why VLC's "live555" demux module calls that function.
>
> --
>
> Ross Finlayson
> Live Networks, Inc.
> http://www.live555.com/
> _______________________________________________
> live-devel mailing list
> live-devel at lists.live555.com
> http://lists.live555.com/mailman/listinfo/live-devel
>
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