[Live-devel] testH264VideoToTransportStream Frame Rates

[Ross Finlayson]

I think you may be confused about the purpose of the initial setting of "fFrameRate" in "H264VideoStreamFramer.cpp".  This setting is just a 'guess' - a default setting, to be used if - for some reason - the stream's frame rate cannot be inferred from reading SPS ("Sequence Parameter Set") NAL units.  But if really shouldn't be used.  Ideally, SPS NAL units will tell you what the stream's frame rate is.  But if this can't be done - e.g., because your stream doesn't have any SPS NAL units - then we have to guess the frame rate.  In the code, we 'guess' 25 fps, but that may, or may not be correct.  The best solution is to have SPS NAL units in your stream that tell you what the frame rate really is.

But in your email, you said that the guess of 25 fps gave you 'reliable video', but when you changed the guess to 10 fps, you got bad video.  This suggests to me that you were trying to 'change' the video's frame rate - which is not the purpose of this code.  If you really want to change a video stream from 25 fps to 10 fps, then you should be dropping frames from the input; not just trying to change the timing information.


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

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