[Live-devel] Subtitle

[Ross Finlayson]

>What about trick play? After what I can see, pause, ffwd, rwd and such
>does not work well with transport stream.

RTSP "PAUSE" works OK with all media types, including MPEG Transport 
Streams.  (However, as I noted in my earlier message, VLC currently doesn't 
implement PAUSE correctly.)  The Amino set-top box, however, will send a 
RTSP "PAUSE" (and the stream stops playing) if the user presses the 'pause' 
button on the remote control.

Seeking (by time) within a MPEG Transport Stream is something that could 
probably be implemented fairly easily.

However, fast forward and reverse play are much more 
difficult.  Implementation of this involves (i) extracting the video 
program from the Transport Stream; (ii) extracting I-frames from the video 
program (because if you're playing only selected video frames - for fast 
forward - then they must be all I-frames); (iii) chosing which I-frames to 
display, to give you the desired speed;  (iv) reassembling the chosen 
I-frames into a new (video-only) Transport Stream; and (v) streaming the 
new Transport Stream (with correct timing).

It turns out that (after a *lot* of effort), I was able to implement RTSP 
fast forward and reverse play on Transport Streams - as described above - 
for a customer's project.  However, this was custom, proprietary code, 
which will probably not get included in the public "LIVE.COM Streaming 
Media" source code release anytime in the near future.


	Ross Finlayson
	LIVE.COM
	<http://www.live.com/>