Hi,
I am trying to figure out how to get the frame width and height out of a H.264
stream and I'm having some difficulties understanding how to decode a SPS.
On the FAQ section on live555.com I found the following:
"If you are receiving H.264 video data, there is one more thing that you have
to do before you start feeding frames to your decoder. H.264 streams have
out-of-band configuration information ("SPS" and "PPS" NAL units) that you may
need to feed to the decoder to initialize it. To get this information, call
"MediaSubsession::fmtp_spropparametersets()" (on the video 'subsession'
object). This will give you a (ASCII) character string. You can then pass this
to "parseSPropParameterSets()" (defined in the file
"include/H264VideoRTPSource.hh<http://www.live555.com/liveMedia/doxygen/html/H264VideoRTPSource_8hh.html>"),
to generate binary NAL units for your decoder."
Unfortunately, I cannot figure out where to go from here. For example, I get
the following SPS
Z2QAKKwrQDwBE/LgIgAAB9AAAdTBHjhlQA==,aO48sA==
which apparently contains two SPropRecord entries of 25 and 4 bytes length,
respectively:
0x67 0x64 00 0x28 0xac 0x2b 0x40 0x3c 0x1 0x13 0xf2 0xe0 0x22 00 00 0x7 0xd0 00
0x1 0xd4 0xc1 0x1e 0x38 0x65 0x40
0x68 0xee 0x3c 0xb0
I found a few sites on the web, giving brief explanations but every one of them
gets ma stuck at some point.
Given that I would expect this to be a quite common task, I wanted to ask if
there are some helper classes/functions in live555 that already prase the SPS
and give me what I want. Otherwise, I would appreciate pointing me to a helpful
source.
Thanks!
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