Enhancement: Better previews for HDR video

lib/private/Preview/Movie.php

@@ -9,11 +9,14 @@
 
 use OCP\Files\File;
 use OCP\Files\FileInfo;
+use OCP\IConfig;
 use OCP\IImage;
 use OCP\Server;
 use Psr\Log\LoggerInterface;
 
 class Movie extends ProviderV2 {
+	private IConfig $config;
+
 	/**
 	 * @deprecated 23.0.0 pass option to \OCP\Preview\ProviderV2
 	 * @var string
@@ -29,9 +32,11 @@ class Movie extends ProviderV2 {
 	/** @var string */
 	private $binary;
 
-	/**
-	 * {@inheritDoc}
-	 */
+	public function __construct(array $config) {
+		parent::__construct($config);
+		$this->config = Server::get(IConfig::class);
+	}
+
 	public function getMimeType(): string {
 		return '/video\/.*/';
 	}
@@ -105,6 +110,32 @@ public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage {
 		return $result;
 	}
 
+	private function useHdr(string $absPath): bool {
+		// load ffprobe path from configuration, otherwise generate binary path using ffmpeg binary path
+		$ffprobe_binary = $this->config->getSystemValue('preview_ffprobe_path', null) ?? (pathinfo($this->binary, PATHINFO_DIRNAME) . '/ffprobe');
+		// run ffprobe on the video file to get value of "color_transfer"
+		$test_hdr_cmd = [$ffprobe_binary,'-select_streams', 'v:0',
+			'-show_entries', 'stream=color_transfer',
+			'-of', 'default=noprint_wrappers=1:nokey=1',
+			$absPath];
+		$test_hdr_proc = proc_open($test_hdr_cmd, [1 => ['pipe', 'w'], 2 => ['pipe', 'w']], $test_hdr_pipes);
+		if ($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]));
+		proc_close($test_hdr_proc);
+		// 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.
+		// Only return true if video is detected as HDR and libzimg is installed.
+		if (($test_hdr_stdout === 'smpte2084' || $test_hdr_stdout === 'arib-std-b67') && $ffmpeg_libzimg_installed !== false) {
+			return true;
+		} else {
+			return false;
+		}
+	}
+
 	private function generateThumbNail(int $maxX, int $maxY, string $absPath, int $second): ?IImage {
 		$tmpPath = \OC::$server->getTempManager()->getTemporaryFile();
 
@@ -116,10 +147,21 @@ private function generateThumbNail(int $maxX, int $maxY, string $absPath, int $s
 				'-an', '-f', 'mjpeg', '-vframes', '1', '-vsync', '1',
 				$tmpPath];
 		} elseif ($binaryType === 'ffmpeg') {
-			$cmd = [$this->binary, '-y', '-ss', (string)$second,
-				'-i', $absPath,
-				'-f', 'mjpeg', '-vframes', '1',
-				$tmpPath];
+			if ($this->useHdr($absPath)) {
+				// Force colorspace to '2020_ncl' because some videos are
+				// tagged incorrectly as 'reserved' resulting in fail if not forced.
+				$cmd = [$this->binary, '-y', '-ss', (string)$second,
+					'-i', $absPath,
+					'-f', 'mjpeg', '-vframes', '1',
+					'-vf', 'zscale=min=2020_ncl:t=linear:npl=100,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p',
+					$tmpPath];
+			} else {
+				// always default to generating preview using non-HDR command
+				$cmd = [$this->binary, '-y', '-ss', (string)$second,
+					'-i', $absPath,
+					'-f', 'mjpeg', '-vframes', '1',
+					$tmpPath];
+			}
 		} else {
 			// Not supported
 			unlink($tmpPath);