box: add webcam input and fix bash conditionals (#3882)

Add INPUT_WEBCAM env var to stream.sh for using a webcam (e.g.
/dev/video0) as video input via v4l2. Document both video file
and webcam input options in box.md.

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rickstaa

box/box.md

@@ -84,6 +84,18 @@ export RTMP_OUTPUT=rtmp://rtmp.livepeer.com/live/$STREAM_KEY
 
 This one is only required for the `box-stream` command. It is useful when you cannot use the `box-playback` command to play the stream, for example when you are using a remote non-UI machine.
 
+### Video Input
+
+By default, `box-stream` uses a generated test pattern. You can use a video file or webcam instead:
+
+```bash
+# Use a video file
+export INPUT_VIDEO=/path/to/video.mp4
+
+# Or use a webcam (Linux)
+export INPUT_WEBCAM=/dev/video0
+```
+
 ### Docker
 If you want to run the box in a docker container, set the `DOCKER` env var:
 ```bash

box/box.sh

@@ -4,14 +4,14 @@ set -e
 DOCKER=${DOCKER:-false}
 FRONTEND=${FRONTEND:-false}
 
-if [ "$FRONTEND" = "true" && "$DOCKER" = "false" ]; then
+if [[ "$FRONTEND" = "true" && "$DOCKER" = "false" ]]; then
   echo "Running the box with FRONTEND=true requires DOCKER=true"
   exit 1
 fi
 
 # Ensure backgrounded services are stopped gracefully when this script is interrupted or exits.
 cleanup() {
-  if [ "$DOCKER" = "true" ]; then
+  if [[ "$DOCKER" = "true" ]]; then
     echo "Stopping dockerized services..."
     docker stop orchestrator --time 15 >/dev/null 2>&1 || true
     docker stop gateway --time 15 >/dev/null 2>&1 || true
@@ -51,7 +51,7 @@ gateway &
 orchestrator &
 mediamtx &
 
-if [ "$FRONTEND" = "true" ]; then
+if [[ "$FRONTEND" = "true" ]]; then
   supabase &
   frontend &
 fi

box/stream.sh

@@ -7,6 +7,7 @@ STREAM_ID="my-stream-id"
 RTMP_OUTPUT=${RTMP_OUTPUT:-""}
 FPS=${FPS:-30}
 INPUT_VIDEO=${INPUT_VIDEO:-""}
+INPUT_WEBCAM=${INPUT_WEBCAM:-""}
 
 case "$1" in
   start)
@@ -22,7 +23,11 @@ case "$1" in
 
     INPUT_FLAGS="-f lavfi -i testsrc=size=1280x720:rate=${FPS},format=yuv420p"
     if [ -n "$INPUT_VIDEO" ]; then
+      echo "Using video file: ${INPUT_VIDEO}"
       INPUT_FLAGS="-stream_loop -1 -i ${INPUT_VIDEO}"
+    elif [ -n "$INPUT_WEBCAM" ]; then
+      echo "Using webcam: ${INPUT_WEBCAM}"
+      INPUT_FLAGS="-f v4l2 -framerate ${FPS} -video_size 1280x720 -i ${INPUT_WEBCAM}"
     fi
 
     ffmpeg -re ${INPUT_FLAGS} \