[Live-devel] RTP MJPEG: strange fourcc format Y42B instead I420

[Brilliantov Kirill Vladimirovich]

Hello!
I use live555 2013.10.25 on my FreeScale iMX53 board.
Now I add MJPEG RTP stream, for this I write class based on
JPEGVideoSource.
For view RTP stream I use follow GStreamer pipeline:
gst-launch -v udpsrc multicast-group=224.1.4.6 port=5000
caps="application/x-rtp, media=(string)video, clock-rate=(int)90000,
payload=(int)96, encoding-name=(string)JPEG" ! rtpjpegdepay !
ffdec_mjpeg ! xvimagesink

I compare pipeline output from live555 stream and GStreamer stream and
found difference in fourcc:
GStreamer:
caps = video/x-raw-yuv, width=(int)1280, height=(int)720,
framerate=(fraction)0/1, format=(fourcc)I420, interlaced=(boolean)false
live555:
caps = video/x-raw-yuv, width=(int)1280, height=(int)720,
framerate=(fraction)0/1, format=(fourcc)Y42B, interlaced=(boolean)false

Unfortunally on http://www.fourcc.org/yuv.php I found very short
information about Y42B:
Weitek format listed as "YUV 4:2:2 planar". I have no other information
on this format.

But why I get this difference if I use one codec?

-- 
Best regards,
Brilliantov Kirill Vladimirovich