On Mon, Jan 11, 2016 at 1:29 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > On 01/08/2016 07:25 AM, Ran Shalit 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 > > I'm not sure what you're doing, but this just works for me (I use yuv420p to > play this back). > > Note: you can find the same code in v4l-utils in contrib/test. That's the code > I used (with you modifications). > > Regards, > > Hans > Right, It works for me. I work with Centos 7.2 which comes with kernel 3.10.0. The YUV420 format are missing there, I understood it after delving into this issue. Thanks you ! 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
