[vlc-devel] Re: Patch in progress - RTSP scale support

Jean-Paul Saman jean-paul.saman at planet.nl
Sat May 20 11:13:12 CEST 2006

Dermot McGahon wrote:
> Rob Casey wrote:
>> This conditional is being triggered as a result of the 
>> b_out_pace_control being set to a false value as a result of 
>> modules/access_output/udp.c setting i_out_pace_nocontrol to true - 
>> Modifying this value gives variable results where at times, playback 
>> rate is modified, but at others it is not. 
> When VLC is used a a client this would be correct as it doesn't have 
> control over the pace of reading
> the input being streamed from the VOD server. In this case the Scale 
> parameter is used as a command
> to the VOD server asking it to only send I-frames for example. The 
> commercial VOD  servers support
> a limited amount of alternative playback speeds, usually one for 
> fast-forward and one for rewind.
> Your setup has VLC as a server and if the GOP size is twelve and Scale 
> is -12/+12 (for example) then
> it should be possible to send only I-frames to the client but what if 
> another value is given? Which parts
> of the should be sent and which omitted? Sending every second P or 
> B-frame won't work.
You could always send a GOP sequence upto the next I frame, like for 
example: I P B B P B B P B B P. Then skip then next n-GOP's etc. This 
even gives you scalable speeds.

Jean-Paul Saman.

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