[Live-devel] RTP/RTSP Streaming Trouble

[Ross Finlayson]

>I have a test video file to you to use.  It is located at 
><file://ftp.gcsd.harris.com/public>ftp.gcsd.harris.com/public, 
>filename "live555_test_stream.ts".  This is a blind FTP server, 
>therefore it will only accept requests for exactly that filename. 
>Also, I believe the policy is to remove the files nightly, so please 
>let me know if you need me to upload the file again for your access. 
>Hopefully you can reproduce what I've been seeing.

The problem with this file is that its PCR timestamps show that it is 
*extremely* VBR - far more than any reasonable stream should be. 
Because the streaming server uses these timestamps to figure out how 
to pace the outgoing stream (i.e., how much to delay after sending 
each network packet), extremely VBR timestamps messes up the 
streaming.

More specifically, here's what's happening with your test file:
As shown by its last timestamp, the stream is 37.78 seconds long, and 
contains 285866 188-byte Transport Packets.  Therefore, on average, 
each Transport Packet should last about 132 ms.  In practice, 
however, the stream's durations vary widely from this average.

E.g., here are the first few PCR timestamps
packet number	diff from last	PCR timestamp	diff from last	duration/packet
============	==========	============	==========	=============
132		132		0.002257		0.002257 
		17 ms
197		65		0.002727		0.000470 
		7 ms
262		65		0.003187		0.000460 
		7 ms
264		2		0.024481		0.021294 
		10647 ms
302		38		0.024754		0.000273 
		7 ms
322		20		0.024896		0.000142 
		7 ms
326		4		0.048253		0.023357 
		5839 ms
454		128		0.049158		0.000905 
		7 ms

I hope you get the picture.  The extremely large jumps in PCR 
timestamp are messing up our streaming server's estimate of how much 
time to delay after sending each network packet.

I don't know whether you really intended this stream to be so 
extremely VBR, but our server is currently not able to properly 
stream files like this.
-- 

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