Re: Streaming live video.
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bencollins
From: <br...@pr...> - 2000-06-09 11:36:56
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On Jun 9, 9:19, Sebastien Rougeaux wrote: > > Brian> It works well with their UST/MSC system, which assigns a 64-bit > Brian> nanosecond accuracy timestamp (relative to machine reset time) and a > Brian> 'media count' (i.e. frame count) to each incoming media unit > Brian> (i.e. frame) around the circular buffer, so you can accurately match up > Brian> similarly-labelled incoming audio, detect dropped frames, etc. Outgoing > Brian> data can also be accurately synced to absolute time and/or other media > Brian> types. In the case of 1394/DV, you would also want to associate DV > Brian> timecode and 'time of day' timestamps to incoming frames. > > I am not familiar with the DV format, but isn't there already some kind of > timestamp encoded in the DV frame already ? I'm not familiar either, but I understand it has an hh:mm:ss:ff timecode or equivalent, as well as an (optional?) time-of-day timestamp so camcorders no longer need to burn it into the video image. The UST/MSC stuff is especially meaningful when capturing from analog sources which don't have their own inherent timestamp. The SGI effectively assigns a timestamp to the video stream as soon as the signal crosses the RCA jack, so there is an absolute time basis with which to relate other incoming/outgoing video, audio, midi events, serial port characters, keypresses etc. (e.g. you can specify that each serial character is to be transmitted at a specific UST time). I only bring it up because at some stage Linux may want a systemic view of media timestamping, and I thought I'd throw it into the melting pot now ... Cheers Brian. -- -- ----------------------------------- Brian Murray Proximity Pty Ltd http://www.proximity.com.au/~brian/ ----------------------------------- |