[Libav-user] How can we set frame size for live stream?

[Wenpeng Zhou]

> I mean this command.
> ffplay -f dshow -i video="Mercury USB2.0 Camera" -s 640x480
> 
> How can we set 640x480 in C++ code?

To quote my original answer:
> > there is libswscale (or the scale filter that uses
> > libswscale) to do the resizing.

See doc/examples/filtering_video.c for an example for on how to use video
filters, doc/examples/scaling_video.c for an example on how to use
libswscale.

Please do not top-post here, it is considered rude, Carl Eugen
-------------------------------------------------
Hi Carl,

Thanks!

But when I use the command ffmpeg -f dshow -list_options true -i
video="Mercury USB2.0 Camera"
It has the option 
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=640x480 fps=30 max s=640x480 fps=30
Because I am newbie to ffmpeg, I suppose we can take the frame with size
640x480 directly.

ffmpeg -f dshow -list_options true -i video="Mercury USB2.0 Camera"
[dshow @ 00a9eb00] DirectShow video device options
[dshow @ 00a9eb00]  Pin "Capture"
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1280x720 fps=30 max s=1280x720
fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1280x720 fps=30 max s=1280x720
fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=640x480 fps=30 max s=640x480 fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=640x480 fps=30 max s=640x480 fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1600x1200 fps=15 max s=1600x1200
fps=15
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1600x1200 fps=15 max s=1600x1200
fps=15
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=800x600 fps=30 max s=800x600 fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=800x600 fps=30 max s=800x600 fps=30
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1920x1080 fps=15 max s=1920x1080
fps=15
[dshow @ 00a9eb00]   vcodec=mjpeg  min s=1920x1080 fps=15 max s=1920x1080
fps=15
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1280x720 fps=10 max
s=1280x720 fps=10
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1280x720 fps=10 max
s=1280x720 fps=10
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=640x480 fps=30 max
s=640x480 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=640x480 fps=30 max
s=640x480 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=352x288 fps=30 max
s=352x288 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=352x288 fps=30 max
s=352x288 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=320x240 fps=30 max
s=320x240 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=320x240 fps=30 max
s=320x240 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=160x120 fps=30 max
s=160x120 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=160x120 fps=30 max
s=160x120 fps=30
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1600x1200 fps=5 max
s=1600x1200 fps=5
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1600x1200 fps=5 max
s=1600x1200 fps=5
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1920x1080 fps=7.5 max
s=1920x1080 fps=7.5
[dshow @ 00a9eb00]   pixel_format=yuyv422  min s=1920x1080 fps=7.5 max
s=1920x1080 fps=7.5
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