<html><head><base href="x-msg://6255/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div lang="EN-GB" link="blue" vlink="purple"><div class="WordSection1" style="page: WordSection1; "><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">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.<o:p></o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; "><o:p> </o:p></div><div style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif; ">Could you tell me how Live555 calculates the time period between calls to ByteStreamFileSource::doReadFromFile() and also where this is implemented in the code.</div></div></div></span></blockquote><div><br></div><div>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).</div><div><br></div><div>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.</div><div><br></div><div>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").</div></div><br><br><div apple-content-edited="true">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">Ross Finlayson<br>Live Networks, Inc.<br><a href="http://www.live555.com/">http://www.live555.com/</a></span></span>
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