fix(previews): ffprobe hangs

Signed-off-by: Andrey Dyakov <adduxa@gmail.com>

Author: adduxa

AUTHORS

@@ -32,6 +32,7 @@
  - Andreas Pflug <dev@admin4.org>
  - Andrew Brown <andrew@casabrown.com>
  - Andrey Borysenko <andrey.borysenko@nextcloud.com>
+ - Andrey Dyakov <adduxa@gmail.com>
  - André Gaul <gaul@web-yard.de>
  - Andy Xheli <axheli@axtsolutions.com>
  - Anna Larch <anna@nextcloud.com>

lib/private/Preview/Movie.php

@@ -289,9 +289,39 @@ private function useHdr(string $absPath): bool {
 		if ($test_hdr_proc === false) {
 			return false;
 		}
-		$test_hdr_stdout = trim(stream_get_contents($test_hdr_pipes[1]));
-		$test_hdr_stderr = trim(stream_get_contents($test_hdr_pipes[2]));
+
+		stream_set_blocking($test_hdr_pipes[1], false);
+		stream_set_blocking($test_hdr_pipes[2], false);
+
+		$test_hdr_stdout = '';
+		$test_hdr_stderr = '';
+
+		while (!feof($test_hdr_pipes[1]) || !feof($test_hdr_pipes[2])) {
+			$read = array_filter([
+				!feof($test_hdr_pipes[1]) ? $test_hdr_pipes[1] : null,
+				!feof($test_hdr_pipes[2]) ? $test_hdr_pipes[2] : null,
+			]);
+			$write = $except = [];
+			if (stream_select($read, $write, $except, 5) === false) {
+				break;
+			}
+			foreach ($read as $pipe) {
+				$chunk = fread($pipe, 8192);
+				if ($chunk === false) continue;
+				if ($pipe === $test_hdr_pipes[1]) {
+					$test_hdr_stdout .= $chunk;
+				} else {
+					$test_hdr_stderr .= $chunk;
+				}
+			}
+		}
+
+		fclose($test_hdr_pipes[1]);
+		fclose($test_hdr_pipes[2]);
 		proc_close($test_hdr_proc);
+
+		$test_hdr_stdout = trim($test_hdr_stdout);
+		$test_hdr_stderr = trim($test_hdr_stderr);
 		// search build options for libzimg (provides zscale filter)
 		$ffmpeg_libzimg_installed = strpos($test_hdr_stderr, '--enable-libzimg');
 		// Only values of "smpte2084" and "arib-std-b67" indicate an HDR video.