On Fri, Jan 8, 2016 at 8:25 AM, Ran Shalit <ranshalit@xxxxxxxxx> wrote: > Hello, > > I am trying to use v4l2 example from API documentation: > inhttp://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html . > As a start, I wanted to first try uding it with vivid (virtual device driver). > I found excelent vivid documentation in the kernel, which is very helpful: > https://www.kernel.org/doc/Documentation/video4linux/vivid.txt > > But on trying to use the example as-is for capturing video frames into > file, and playing the file, I encounter difficulties. > I tried the example as-is, and then tried several resolution, > pixelformat, different inputs, but it always result with video with a > sync problems ( the test bars of the video are keep moving in the > horizontal axis, or the text is changing its location for one frame to > the next). > > I compiled the v4l2 API example AS-IS from: > http://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html with > minor modification in the --force part of the example (I also tried > the example as is without modifications but it did not help), so that > I choose hd input , and 1920x1080 resolution, V4L2_PIX_FMT_YUV420 > (also tried V4L2_PIX_FMT_YUV422P) , progressive. > > if (force_format) { > input = 3; // <<-- HD input device > if (-1==xioctl(fd,VIDIOC_S_INPUT,&input)) > { > errno_exit("VIDIOC_S_INPUT"); > } > fmt.fmt.pix.width = 1920; > fmt.fmt.pix.height = 1080; > fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420; // <<- > tried also V4L2_PIX_FMT_YUV422P > fmt.fmt.pix.field = V4L2_FIELD_NONE; // <- trying to > capture progressive > > if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt)) > errno_exit("VIDIOC_S_FMT"); > > } else { > > I run the application with (the compiled code using pixelformat = > V4L2_PIX_FMT_YUV420 trial ): > > ./v4l2_example -f -o -c 10 > cap_yuv420p.yuv > > And (the compiled code using pixelformat = V4L2_PIX_FMT_YUV422P trial ) > > ./v4l2_example -f -o -c 10 > cap_yuv422p.yuv > > I've tried to play them with: > > ffplay -f rawvideo -pixel_format yuv420p -video_size 1920x1080 -i > cap_yuv420p.yuv > > And > > ffplay -f rawvideo -pixel_format yuv422p -video_size 1920x1080 -i > cap_yuv422p.yuv > > These are the captured video files from my above trials: > > https://drive.google.com/folderview?id=0B22GsWueReZTUS1tSHBraTAyZ00&usp=sharing > > I probably am doing something wrong. Is there any idea what's wrong in > my configurations or how I can debug it better ? > > Best Regards, > Ran Hi, I did manage to play the video with the example as-is (no code modification) But It seems that the captured video is always the same: 422 YUYV. I tried to change in code to other formats (in the section below force option as I wrote in the previous post) , but although it gives no error (and VIDIOC_G_FMT returns the new format) , and yet - the final video is always in 422, YUYV format. Is there any hint why we can't change the format to YUV420 ? Regards, Ran -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
