<div dir="ltr">thank, the explanation is clear.<div>I'd simply add nv12 to my weston shm_formats.</div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">Nicolas Dufresne <<a href="mailto:nicolas@ndufresne.ca">nicolas@ndufresne.ca</a>> 于2019年5月9日周四下午7:40写道： </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Le jeudi 09 mai 2019 à 11:04 +0800, Halley Zhao a écrit : > Hi experts: > v4l2h264dec claims it supports "video/x-raw" format only, but it may use dmabuf format (its capture-io-mode supports rw/mmap/userptr/dmabuf/dmabuf-import). should it add "video/x-raw(memory:DMABuf)" as well. > on nxp imx8 bsp, I found caps negotiation goes with "video/x-raw" (diskplay->shm_formats), but buffer flows with dmabuf(display->dmabuf_formats), because there is gst_wl_linux_dmabuf_construct_wl_buffer() in log. v4l2h264dec always output DMABuf. DMABuf is user mappable memory, there is no need to have a caps feature in general. The DMABuf caps feature was added for specific use cases, to support implicit tiling (Intel GFX, and that was actually a bad idea), to support protected FDs (non- readable DMABuf, use to carry DRM content) and is open for future support for proprietary formats (like the one exposed through DRM modifiers). The caps feature implement is quite partial overall. > > I met issue that caps negotiation fails between v4l2h264dec and waylandsink, > because on my platform (imx8 + customized weston), v4l2h264dec claims it support video/x-raw with NV12 format, waylandsink claims it support video/x-raw without NV12 format, plus video/x-raw(memory:DMABuf) with NV12 format. Compositors cannot guaranty availability of HW planes. Thus, it is important to provide a fallback mechanism (usually through the GL renderer) and then offer the same formats for both DMABuf and SHM. waylandsink will send DMABuf if the format is supported through the extension even without the caps feature. Of course, if you prefer hard failure if DMABuf isn't used, you may want to implement DMABuf caps feature support in v4l2 plugin. Patches are welcome, though be aware that negotiation of that feature should be last resort (chosen last). Nicolas > _______________________________________________ > gstreamer-devel mailing list > <a href="mailto:gstreamer-devel@lists.freedesktop.org" target="_blank">gstreamer-devel@lists.freedesktop.org</a> > <a href="https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a> _______________________________________________ gstreamer-devel mailing list <a href="mailto:gstreamer-devel@lists.freedesktop.org" target="_blank">gstreamer-devel@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel</a></blockquote></div>