Le vendredi 20 août 2021 à 08:55 +0000, trung1.dothanh@xxxxxxxxxxxxx a écrit : > Hello, > > I am trying to play video with Gstreamer on a fullHD monitor. The board I’m using is Apalis iMX6. > Playing video works great with v4l2h264dec: > > gst-launch-1.0 filesrc location=1080.mkv ! matroskademux ! h264parse \ > ! v4l2h264dec capture-io-mode=dmabuf \ > ! kmssink > > However, it fails to scale video to 720p with v4l2convert: > > gst-launch-1.0 filesrc location=1080.mkv ! matroskademux ! h264parse \ > ! v4l2h264dec capture-io-mode=dmabuf \ > ! v4l2convert output-io-mode=dmabuf-import \ > ! video/x-raw,width=1280,height=720 \ > ! kmssink > > Added some debugs and I found that it failed at 'drivers/media/common/videobuf2/videobuf2-v4l2.c:__verify_length()'. > > length = (b->memory == VB2_MEMORY_USERPTR) Wrong snippet ? You are using VB2_MEMORY_DMABUF according to your GStreamer pipeline. > ? b->length : vb->planes[0].length; > if (b->bytesused > length) > return -EINVAL; > > The “b->byteused” is 4177920 (= 2 x 1920 x 1088), while plane length is just 4147200 (= 2 x 1920 x 1080). > The actual frame size of H264 video is 1920x1088, so I added a bypass for this case and video can be scaled, > but that may not a correct way to fix this problem. > > Is this a bug or I need to do extra steps before scale video? I'm not fully certain of what has gone wrong, since this call was added (1.18.0), this code path is supposed to work: https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/blob/master/sys/v4l2/gstv4l2transform.c#L905 GStreamer will update the driver FMT to padded width/height before calling streamon and S_SELECTION is used to tell the scaler which part is to be used in the scaling process. > > Packages version in my environment are: > * Kernel: 5.10.19 > * Gstreamer: 1.18.4 > > Thank you, > Trung >
