Ross Finlayson escribió:
I am developing a video streaming server to play H.264 SVC stream.
This codec has a base layer (similar to the H.264 AVC one) and one or
more enhancement layers.
I've just created a server to play H.264 AVC stream (an extension of
live555MediaServer.exe), with my own H264StreamFramer and
H264VideoFileServerMediaSubsession classes. I've introduced NAL
packetizer and STAP-A Aggregation to the library too.
Follow to the "RTP Payload Format of SVC Video" draft, I suppose I
have to create a new RTSP session for each layer. Then, I must send
each layer as an independient RTP stream. I dont' know how to start
more than one RTP stream in a single RTSP request, and how to
indicate the receivers that they must download all the streams (I
imagine that the last task will be related with SDP file). I don't
really know what changes do I have to make in the library, and what
classes should I modify.
First, be warned that the SVC video RTP payload format draft is still
that - a draft. It won't become stable until sometime after the next
IETF meeting (July, in Dublin).
To support SVC video at the server end, you would probably need to
create a new "ServerMediaSubsession" (subclass) object for each layer
- but these would share a single "ServerMediaSession". I.e., you
would need to define two new "ServerMediaSubsession" subclasses - one
for the base layer, and one for the enhancement layer(s).
One issue that you'll encounter is that we currently don't support
multiplexing more than one payload format code on the same RTP port
number. Fixing this at the server end (which is where you're working)
may not be particularly difficult. (Fixing it at the client end would
be significantly harder.)
Apart from this, I haven't yet thought much about what would need to
be done. (Unfortunately I don't have a source of SVC video (not even
a file) available, so right now I can't do any work on this myself.)
Hi Ross,
Thanks for your quick answer.
I don't understand very well what you want to say about the payload
format code on the same RTP port number. On the server point of view, I
am trying to send each layer on his own RTSP stream . If I changed RTP
and RTCP port on each RTSP stream (I could configure this more or less
easly), should I have problems?. It will be implemented if I create a
new RTP Sink(s) for the enhancement layer(s)
I am trying to send a SVC file with my AVC implemented solution. It runs
perfectly. But on this way we don't have the SVC advantages.We can't
manage the stream if I don't have enough throughput to receive the
complete stream (and despite I won't develop the client, I must really
think about it).
I want to ask you another question about the library. I implemented
STAP-A Aggregation with a subclass derived from H264VideoStreamFramer. I
can't aggregate the first NAL units in the file (SPS -Type 7- PPS-Type
6- NAL units). However, I can aggregate the NALU type 1 without
problems. I don't really know why is it, can you bring some light about you?
Thakns for all.
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