Add --group-add example in README.md

Signed-off-by: James Ketrenos <james.p.ketrenos@intel.com>

README.md

@@ -6,6 +6,27 @@ offload for transcode operations.
 For information on how the Dockerfile in this container is generated,
 see [xe-solutions](https://gitlab.devtools.intel.com/vtt/sws/osgc/solutions/xe-solutions).
 
+# To run pre-built container
+The following will download the latest version of the container and run the 
+'test' entry point.
+
+```bash
+. SOLUTION
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
+docker run --rm \
+  --group-add ${VIDEO} \
+  --volume $(pwd)/data:/data \
+  --device /dev/dri \
+  ${REGISTRY_URL}/intel-compute-clinfo:latest-${OS_DISTRO}-${OS_RELEASE} \
+  test
+```
+
+NOTE: The VIDEO setup prior to running the container is needed if you are running
+on a host OS that has a different video UID:GID mapping than the guest OS.
+
+On some systems, you may also need to do the same for the RENDER group. See
+`scripts/test-image.sh` for an example.
+
 # Usage examples
 
 Two step from zero-to-hero:
@@ -29,7 +50,9 @@ The following will transcode 'TearsOfSteal.mp4' from AVC (H.264) to a
 5Mbps HEVC (H.265) stream using the GPU.
 
 ```bash
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
 docker run \
+  --group-add ${VIDEO} \
   --device=/dev/dri \
   --volume $(pwd)/data:/data \
   amr-registry.caas.intel.com/vtt-osgc/solutions/intel-media-ffmpeg:ubuntu-eoan \
@@ -93,7 +116,9 @@ scripts/build-image.sh
 
 ```bash
 TAG=${TAG:-latest}
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
 docker run \
+  --group-add ${VIDEO} \
   --rm \
   --device=/dev/dri \
   -e QSV_DEVICE=${QSV_DEVICE:-/dev/dri/renderD128} \
@@ -122,7 +147,9 @@ TAG=${TAG:-latest}
 mkdir $(pwd)/data
 wget -O $(pwd)/data/AUD_MW_E.264 \
   https://fate-suite.libav.org/h264-conformance/AUD_MW_E.264
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
 docker run \
+  --group-add ${VIDEO} \
   --rm \
   --device=/dev/dri \
   -e QSV_DEVICE=${QSV_DEVICE:-/dev/dri/renderD128} \
@@ -164,7 +191,9 @@ TAG=${TAG:-latest}
 mkdir $(pwd)/data
 wget -O $(pwd)/data/TearsOfSteel.mp4 \
   http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/TearsOfSteel.mp4
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
 docker run \
+  --group-add ${VIDEO} \
   --rm \
   --device=/dev/dri \
   -e QSV_DEVICE=${QSV_DEVICE:-/dev/dri/renderD128} \
@@ -180,7 +209,9 @@ The examples below are all assumed to be running in the container's environment:
 
 ```bash
 TAG=${TAG:-latest}
+VIDEO=$(getent group video  | sed -E 's,^video:[^:]*:([^:]*):.*$,\1,')
 docker run \
+  --group-add ${VIDEO} \
   --rm \
   --device=/dev/dri \
   -e QSV_DEVICE=${QSV_DEVICE:-/dev/dri/renderD128} \