[Live-devel] rtspTestClient consumes the first bytes of each packet? How to prevent?

[Ross Finlayson]

> On May 30, 2019, at 2:30 PM, Chris Paucar <chris.paucar at roc-connect.com> wrote:
> 
> Hi Eric,
> 
> Regarding #3, those are the SPS and PPS NAL units, size 22 and 4 respectively. You can confirm by looking at the 5 lower bits of the first byte and matching the NAL unit type with values 7 and 8 for SPS and PPS. 
> 
> Some RTSP sources provide them in a separate stream

This is not quite correct.  The SPS and PPS NAL units are encoded in the stream’s SDP description (which RTSP retrieves in response to its “DESCRIBE” command, before starting the actual streaming).  This is not “a separate stream” - it’s just a part of the stream’s (static) description, which RTSP retrieves at the beginning of the protocol exchange.

These NAL units *may* (or may not) also appear (either only at the start, or periodically) inside the RTP video stream.  In Eric’s case, it appears that they do appear in the stream.  This is not necessary, however, because they (as noted above) are also coded in the stream’s SDP description.


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