[Live-devel] openRTSP, Trick Mode, and Transport Streams

[Rutherford, Robert]

Ross,

I was not running the latest baseline before, so I tried that and I get
the same result.  Also, I used Wireshark to trace the RTSP commands to
setup the stream and everything looks the same (i.e. OPTIONS, DESCRIBE,
SETUP, PLAY). The 1.0 scale immediately starts sending the RTP packets
after the setup.  The 2.0 scale sends a TCP message (appears to be an
ACK) immediately after the "OK" response to the PLAY command, but never
sends any RTP packets.  I don't see any errors on the server or client
side (in the form of prints), but I am also not sure I have the most
verbose output on.  I am using MPEG2 Transport Streams and version
2007.07.09.


Rob Rutherford
Harris Corporation

------------------------------

>I am able to test trick mode functionality using 
>testMPEG2TransportStreamTrickPlay at various scales and in both 
>directions.  However, when I try to test with openRTSP I see some 
>strange results.  I modified the call to the function 
>playMediaSession() as you describe in a previous thread ("Trick play 
>problems", 4/16/2007) to accept arguments for start time, end time, 
>and scale.  I am using a start time of 0.0f and an end time of 
>-1.0f.  With a scale of 1.0f, everything works well, with openRTSP 
>creating a file (video-MP2T-1) locally.  When I try scale = 2.0f, it 
>still creates the same file, but with the same size and scale as the 
>first (verified by playback with VLC).  If I try scale = 4.0f, 
>openRTSP creates the file video-MP2T-1, but it remains at size zero 
>and openRTSP appears to do nothing.

That's odd.  Are you using the latest version of the code?  (Version 
2007.07.01 fixed a bug that affected 2x speedup (although it should 
not have affected 4x speedup).)

I have tested the latest version of the code (2007.07.10), and it 
works OK for me.

(In each case, I modified the call to "playMediaSession()" at line 65 
of "testProgs/openRTSP.cpp".


>  I need a method of verifying trick mode over RTSP.  Also, the 
>directions for using Trick Mode state that the scale must be an 
>integer.  This means that scales less than 1 are not support (i.e. 
>slow motion)?

Not for Transport Streams, with our implementation.
-- 

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