[Live-devel] Change to 'trick play' Transport Stream generation - reduces output bit rate

[Ross Finlayson]

Some people have reported having problems with 'trick play' 
operations on Transport Streams, due to the high bitrate of the 
'trick play' output streams.

By popular demand, I have now released a new version (2009.02.23) of 
the "LIVE555 Streaming Media" software that changes the way that 
Transport Streams are generated for 'trick play' operations 
(fast-forward or reverse play).  Now, each I-frame (i.e., key frame) 
appears no more than once in the output Transport Stream for 'trick 
play' operations.  This will have the effect of reducing the average 
output bitrate for 'trick play' streams, except for high 'scale' 
values.

For those of you who have been having problems with the high bit rate 
of 'trick play' Transport Stream data - please try this new code, and 
let us know if this new version of the code improves things.  Note 
that because these changes are experimental, I have not yet changed 
the prebuilt binary versions of the "LIVE555 Media Server" 
application - therefore, if you use this application, you will need 
to build your own version from the new source code.

If - for whatever reason - you wish to go back to the old behavior 
(in which we always keep the original frame rate, even if it means 
duplicating I-frames), then you can do so by changing the definition 
of "KEEP_ORIGINAL_FRAME_RATE" in 
"liveMedia/MPEG2TransportStreamTrickModeFilter.cpp" to "True". 
However, if you find you need to do this, please let us know why. 
This change to the code is experimental, and I will back it out if 
people end up having problems with it.
-- 

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