Changes between Version 49 and Version 50 of DirectShow


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Timestamp:
Aug 26, 2018, 7:16:58 AM (8 months ago)
Author:
rogerdpack
Comment:

typos

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  • DirectShow

    v49 v50  
    114114You can set framerate like {{{ffmpeg -f dshow -framerate 7.5 -i video=XXX}}}.  This instructs the device itself to send you frames at 7.5 fps [if it can].
    115115
    116 Be careful *not* to specify framerate with the "-r" parameter, like this  {{{ffmpeg -f dshow -r 7.5 -i video=XXX}}}.  This actually specifies that the devices incoming PTS timestamps be *ignored* and replaced as if the device were running at 7.5 fps [so it runs at default fps, but its timestamps are treated as if 7.t fps].  This can cause the recording to appear to have "video slower than audio" or, under high cpu load (if video frames are dropped) it will cause the video to fall "behind" the audio [after playback of the recording is done, audio continues on--and gets highly out of sync, video appears to go into "fast forward" mode during high cpu scenes].
    117 
    118 If you want say 10 fps, and you device only supports 7.5 and 15 fps, then run it at fps then "downsample" to 10 fps.  There are a few ways to do this--you could specify your output to be 10 fps, like this: {{{ffmpeg -f dshow -framerate 15 -i video=XXX -r 10 output.mp4}}} or insert a filter to do the same thing for you: {{{ffmpeg -f dshow -framerate 15 -vf fps=15 output.mp4}}}.
     116Be careful *not* to specify framerate with the "-r" parameter, like this  {{{ffmpeg -f dshow -r 7.5 -i video=XXX}}}.  This actually specifies that the devices incoming PTS timestamps be *ignored* and replaced as if the device were running at 7.5 fps [so it runs at default fps, but its timestamps are treated as if 7.5 fps].  This can cause the recording to appear to have "video slower than audio" or, under high cpu load (if video frames are dropped) it will cause the video to fall "behind" the audio [after playback of the recording is done, audio continues on--and gets highly out of sync, video appears to go into "fast forward" mode during high cpu scenes].
     117
     118If you want say 10 fps, and you device only supports 7.5 and 15 fps, then run it at 15 fps then "downsample" to 10 fps.  There are a few ways to do this--you could specify your output to be 10 fps, like this: {{{ffmpeg -f dshow -framerate 15 -i video=XXX -r 10 output.mp4}}} or insert a filter to do the same thing for you: {{{ffmpeg -f dshow -framerate 15 -vf fps=15 output.mp4}}}.
    119119
    120120