[Live-devel] SOCKLEN_T type / AC3AudioStreamParser try-catch / AC3 stream header

[Jeff Shanab]

 I just built and ran live555 and the proxyRtsptest app on my raspberry PI and I didn't have to change a thing.
________________________________
From: live-devel-bounces at ns.live555.com [live-devel-bounces at ns.live555.com] on behalf of Ross Finlayson [finlayson at live555.com]
Sent: Tuesday, March 19, 2013 12:30 PM
To: LIVE555 Streaming Media - development & use
Subject: Re: [Live-devel] SOCKLEN_T type / AC3AudioStreamParser try-catch / AC3 stream header

I compiled and ran live555 on Raspberry Pi but I changed the type of SOCKLEN_T

For the bazillionth time: Please DO NOT change the supplied code!  (I want to make it as easy as possible for you to comply with the LGPL :-)


Int works fine on windows but it’s unsigned int on the PI.

Does your development environment for the 'Raspberry Pi' (Linux, right?) not already define "socklen_t"??  If it does, then you should be able to use the existing "config.linux" configuration file.  But even if it doesn't, there's a very easy way to make this change, without having to modify the supplied code:

Create a "config.linux-for-raspberry-pi" configuration file (perhaps just by copying "config.linux"), and, in the 'COMPILE_OPTS' line, set
-DSOCKLEN_T="unsigned int"
(I'm not sure about the quoting there; you might need to use single quotes instead?)

(If you find that you need to create a separate "config.linux-for-raspberry-pi" configuration file, then please share it on the mailing list, so I can include it in future software releases.)


I noticed a try/catch block in liveMedia\AC3AudioStreamFramer.cpp is this intentional?

Of course it's intentional; I wouldn't write that code for no reason :-)


Since my  compiler stumbled over try/catch (exceptions turned off)

Sorry, but that won't work.  To compile our code, your C++ compiler needs to understand C++ language exceptions.  (I wish this weren't true, but we use C++ exceptions for stream parsing; getting rid of them would be difficult.)


I came across (liveMedia/AC3AudioStreamFramer.cpp)

// We expect an AC3 audio header (first 2 bytes == 0x0B77) at the start:
    while (1) {
      unsigned next4Bytes = test4Bytes();
      if (next4Bytes>>16 == 0x0B77) break;
      skipBytes(1);
      saveParserState();
    }

AC3 streams are WORD oriented and both endianness’ are possible.

Are you saying that both orders are possible *in the stream*??  I don't think that's true.  The AC-3 specification says, I think, that all values are sent in 'big endian' order (i.e., high-order byte first).  Our "test4Bytes()" code reads the next 4 bytes - one at a time - from the stream, always returning a 'big endian' result (regardless of the byte order of the host computer).  So the code of ours that you quoted is correct, I believe.


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






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