[Live-devel] JPEGVideoRTPSink and Restart markers

[Francisco Feijoo]

Thanks Cristiano!, I'm going to add the restart marker header as you are
showing.

2010/10/27 Cristiano Belloni <belloni at imavis.com>

>  Il 27/10/2010 02:39, Ross Finlayson ha scritto:
>
> I'm trying to create a rtsp server to stream MJPEG images.
>
>
> Ugh.  JPEG is a *terrible* codec for video streaming.
>
>
> I agree, but *everyone* requests JPEG as an entry point. Onvif, for
> example, requests MJPEG/RTP streaming as a MUST IMPLEMENT.
>
>
>
>
>  I have implemented a new TestJPEGFileServerMediaSubsession that creates a
> TestJPEGVideoRTPSink.
>
> In TestJPEGVideoRTPSink::doSpecialFrameHandling I'm adding the quantization
> tables of the image into the header using setSpecialHeaderBytes
>
>
> Note that the existing "JPEGVideoRTPSink" code already does this. You
> should not have to reinvent the wheel here.
>
>
> This is working fine using some JPEG images, but fails with others.
>
> I'm testing one image that has the marker 0xFF, 0xDD ( Define Restart
> Interval) and I think I have to do something else seeing this comment in the
> code
>
> // Note: We assume that there are no 'restart markers'
>
> So, what should I do with images containing restart markers and
> macroblocks?
>
>
> The JPEG transmitting code ("JPEGVideoSource" and "JPEGVideoRTPSink")
> currently don't support "Restart Marker Headers" (see RFC 2435, section
> 3.1.7).  You will need to update the (definition and implementation) of
> these two classes to support them.
>
> I did something similar, Francisco. In a nutshell, you've got to extend
> JPEGVideoSource and look for DRI markers like this:
>
>  //Look for the DRI marker
>     for (unsigned i = 0; i < JPEGHeaderSize; ++i) {
>         if (fBuffer[i] == 0xFF) {
>             if (fBuffer[i+1] == 0xDD) { // DRI
>                 if ((fBuffer[i+2] != 0) || (fBuffer[i+3] != 4)) {
>                     envir() << "Wrong DRI marker!\n";
>                     continue;
>                 }
>                 else {
>                     fRestartInterval = (fBuffer[i+4] << 8) + fBuffer[i+5];
>                     printf ("DRI restart Interval found @ %d is %d\n", i,
> fRestartInterval);
>                     break;
>                 }
>             }
>         }
>     }
>
> Then, extend JPEGVideoRTPSink to take care about the restart markers in
> doSpecialFrameHandling():
> (In reality, here I extended VideoRTPSink because I needed to, feel free to
> do your adaptations)
>
> u_int8_t RestartMarkerHeader[4]; // the special header
> u_int16_t restartInterval = source->restartInterval();
>
> RestartMarkerHeader[0] = restartInterval >> 8;
> RestartMarkerHeader[1] = restartInterval;
> RestartMarkerHeader[2] = 0xFF;
> RestartMarkerHeader[3] = 0xFF;
>
> setSpecialHeaderBytes(RestartMarkerHeader, sizeof RestartMarkerHeader,
> sizeof mainJPEGHeader /* start position */);
>
> Finally, reflect the size change in the headers in specialHeaderSize():
>
> // We assume that there are 'restart markers'
> headerSize += 4;
>
> --
> Belloni Cristiano
> Imavis Srl.
> www.imavis.com
> belloni at imavis.com <//belloni at imavis.com>
>
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>
>


-- 
Francisco Feijoo
Software Engineer
J2K Video Limited

T: +34 654967246
E: francisco at j2kvideo.com
W: www.j2kvideo.com
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