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--></style><title>Re: [Live-devel] question about fmtp fields for
MJPEG RTP</title></head><body>
<blockquote type="cite" cite>I work in Elphel, Inc (<a
href="http://www3.elphel.com/index.php"
>http://www3.elphel.com/index.php</a>), we make high resolution
network videocamera, what send videostream over RTP/RTSP in MJPEG and
Theora format.</blockquote>
<div><br></div>
<div>I assume you're familiar with our Elphel server application
code:<font face="Lucida Grande" size="-4" color="#000000">
http://www.live555.com/Elphel/</font></div>
<div><br></div>
<blockquote type="cite" cite>I have question, about dynamic payload
type for MJPEG in live555 library.<br>
<br>
RTP MJPEG RFC format with payload #26 have limitation for image size -
each size of image must be less than 2040 pixels, and larger size not
supported. In current live555 code exist hack for this limitation - if
width or height in MJPEG header == 0 - used 2048 size (what in general
not correct, but ok for 3MPx sensors with 2048x1536 image). We start
use 5MPx sensors, and get again this problem.<br>
In SDP parser (of live555 library) exist parser of field
"a=x-dimensions:WW,HH", but this data used only for
container - not when we restore JPEG headers from MJPEG packets; and
also, in code, in this time we can't get access to this properties
(MediaSubsession::videoWidth(), MediaSubsession::videoHeight() ) of
subsession from JPEG packet implementation class.<br>
<br>
I ask about add support for this in live555 - use width and height
from subsession description, when we make JPEG headers from MJPEG
(JPEG images have limit to 65526 pixels, not in 2040, so all must be
ok with JPEG headers).<br>
</blockquote>
<blockquote type="cite" cite>And also, if this feature possible - may
be, in live555 can be used for image size not only this extension
("a=x-dimensions:..."), but attributes from SDP
"a=fmtp: width=WW; height=HH" attributes, like in drafts of
RTP Theora, or RTP JPEG2000? In general, it's easy, if we can get
access to subsession description from JPEG header class.</blockquote>
<div><br></div>
<div>I'm generally reluctant to support attributes (like
"x-dimensions") or payload formats that are not official
IETF standards, or on the standards track.</div>
<div><br></div>
<div>It wasn't clear (to me) from your message exactly what it is that
you are asking for. Are you asking it/when we will support the
JPEG 2000 RTP payload format <<font face="Lucida Grande" size="-4"
color="#000000"
>http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-jpeg2000-12.t<span
></span>xt</font>>? Or are you asking that we support a
non-standard SDP attribute with the RFC 2435 MJPEG RTP Payload
Format? (If it's the latter, then I would be very reluctant to
do this.)</div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div><br>
Ross Finlayson<br>
Live Networks, Inc.<br>
http://www.live555.com/</div>
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