> I’m having difficulty streaming live H264 video captured from a PCI Express > board. It appears that the data acquisition is too slow for the Live555 > streaming application and hence the displayed video (in VLC) is sticky. For > the time being I am assuming that the hardware is okay and would like to > investigate the possibility that the Live555 application is attempting to > grab the data too quickly for the hardware. > > Could you tell me how Live555 calculates the time period between calls to > ByteStreamFileSource::doReadFromFile() and also where this is implemented in > the code.
You haven't said exactly how you're reading H.264 data from your video capture device, but because you mentioned "ByteStreamFileSource", I'm assuming that you're treating the device as a file (a byte stream), and feeding the output from a "ByteStreamFileSource" (i.e., your video capture device) into a "H264VideoStreamFramer" (which parses the byte stream into a sequence of H.264 NAL units). In this case, the code (in "H264VideoStreamFramer") figures out the frame rate (and thus, how long to delay between frames) from the "time_scale" parameter in "Sequence Parameter Set" (i.e., SPS) NAL units. If this parameter is not present, then the code can't figure out the frame rate, so it uses a default frame rate of 25 fps. If, however, your video capture device delivers 'discrete' H.264 NAL units - i.e., one at a time - rather than an unstructured byte stream, then you should *not* attempt to read it as a file. Instead, you should write your own subclass of "FramedSource" (perhaps, based on the "DeviceSource" model) that delivers the NAL units, and feed these into a "H264VideoStreamDiscreteFramer" - *not* a "H264VideoStreamFramer". If you do this, then your 'input device' class - i.e., the subclass of "FramedSource" that you'll write - *must* set "fDurationInMicroseconds" for each NAL unit, before it delivers it to its downstream object (a "H264VideoStreamDiscreteFramer"). Ross Finlayson Live Networks, Inc. http://www.live555.com/
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