[Live-devel] SDP headers x-dimensions and x-framerate VS. a=framerate: 25 and a=framesize:96 720-480

[Ross Finlayson]

>I note liveMedia parses x-dimensions and x-framerate in SDP while 
>some servers use a=framerate: 25 and a=framesize:96 720-480 to 
>represent the video frame size as well as framrate. I'm confused and 
>find no clues which one is standard or adopted popularly.

The "x-" prefix for "x-dimensions" and "x-framerate" indicates that 
these are experimental (i.e., non-standard) SDP attributes.  They 
are, however, used by some QuickTime-based video servers, which is 
why I chose to support them in the "LIVE555 Streaming Media" code.

The "framerate" attribute is defined in RFC 4566 - the latest version 
of the SDP specification.    Therefore it is a standard, and because 
of this, it will be supported in the LIVE555 code shortly.

However, I have not seen any RFC (or Internet-Draft) that defines the 
"framesize" attribute.  Therefore, it is probably not a standard, and 
should not be used (because it doesn't have a "x-" prefix).  It will 
probably not get supported in the LIVE555 code.