Play V4l2 video source on framebuffer

[Nicolas Dufresne]

Le mercredi 31 mars 2021 à 15:08 -0500, jamesM a écrit :
> Hi
> I installed Ubuntu server 20.04 (without GUI) on my desktop PC and also
> installed video capture card on my PC.
> i wanna play real time Pal camera frame(720*576 )on framebuffer but i cant 

Can you define what "on framebuffer" means to you ? It's been a long time that
the Linux kernel have deprecate the FrameBuffer interface in favour of DRM/KMS.
Are you referring to this legacy ?

> 
> 
> 
> > > v4l2-ctl --all
> Driver Info:
> 	Driver name      : tw686x
> 	Card type        : tw6864
> 	Bus info         : PCI:0000:01:00.0
> 	Driver version   : 5.4.94
> 	Capabilities     : 0x85200001
> 		Video Capture
> 		Read/Write
> 		Streaming
> 		Extended Pix Format
> 		Device Capabilities
> 	Device Caps      : 0x05200001
> 		Video Capture
> 		Read/Write
> 		Streaming
> 		Extended Pix Format
> Priority: 2
> Video input : 0 (Composite0: ok)
> Video Standard = 0x0000b000
> 	NTSC-M/M-JP/M-KR
> Format Video Capture:
> 	Width/Height      : 720/480
> 	Pixel Format      : 'UYVY' (UYVY 4:2:2)
> 	Field             : Interlaced
> 	Bytes per Line    : 1440
> 	Size Image        : 691200
> 	Colorspace        : SMPTE 170M
> 	Transfer Function : Default (maps to Rec. 709)
> 	YCbCr/HSV Encoding: Default (maps to ITU-R 601)
> 	Quantization      : Default (maps to Limited Range)
> 	Flags             : 
> Streaming Parameters Video Capture:
> 	Capabilities     : timeperframe
> 	Frames per second: 30.000 (30/1)
> 	Read buffers     : 3
> 
> User Controls
> 
>                      brightness 0x00980900 (int)    : min=-128 max=127
> step=1 default=0 value=0 flags=slider
>                        contrast 0x00980901 (int)    : min=0 max=255 step=1
> default=100 value=100 flags=slider
>                      saturation 0x00980902 (int)    : min=0 max=255 step=1
> default=128 value=128 flags=slider
>                             hue 0x00980903 (int)    : min=-128 max=127
> step=1 default=0 value=0 flags=slider
> 
> 
> > > gst-launch-1.0 v4l2src device="/dev/video0" !
> "video/x-raw,width=640,height=576,format=(string)YUY2" !
> fbdevsink="/dev/fb0"
> 
>  WARNING:errorneous pipeline:could not link v4l2src0 to fbdevsink0 ,
> fbdevsink0 cant handle
> video/x-raw,width=(int)720,height=(int)576,(string)YUY2

Perhaps you should read a bit more about GStreamer and constructing pipelines ?
In this case, you are missing a color conversion, since a framebuffer is always
in RGB colorspace (e.g. videoconvert). Also fbdevsink= is a syntax error. You
probably meant to write fbdevsink device=...

If you care about performance, use kmssink or glimagesink, they can both display
without a video server (except on NVIDIA proprietary driver, which does not
implement the required bits).

> 
> 
> 
> 
> 
> It seems gstreamer pipeline need some filters  would you please help me what
> kind of filters should i use?
> 
> 
> 
> --
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