Seems quicktime atoms can have multiple mdat's, so we need a way to calculate our signature for them too

app/Media/Base.php

@@ -17,6 +17,7 @@ abstract class Base
 	private mixed $fh;
 	private int $fp;
 
+	protected Collection $cache;
 	protected ?string $unused_data;
 
 	public function __construct(string $filename,string $type)
@@ -26,6 +27,7 @@ abstract class Base
 		$this->filename = $filename;
 		$this->filesize = filesize($filename);
 		$this->type = $type;
+		$this->cache = collect();
 	}
 
 	/**
@@ -38,8 +40,9 @@ abstract class Base
 	public function __get(string $key): mixed
 	{
 		switch ($key) {
+			case 'fh':
 			case 'type':
-				return $this->type;
+				return $this->{$key};
 
 			default:
 				throw new \Exception('Unknown key: '.$key);

app/Media/QuickTime.php

@@ -40,9 +40,16 @@ class QuickTime extends Base {
 
 			// Signatures are calculated by the sha of the MDAT atom.
 			case 'signature':
-				$atom = $this->find_atoms(mdat::class,1);
+				if (! $this->cache->has('signature')) {
+					$hash = NULL;
 
-				return $atom->signature;
+					foreach ($this->find_atoms(mdat::class) as $atom)
+						$hash = $atom->signature('sha1',$hash,TRUE);
+
+					$this->cache->put('signature',hash_final($hash));
+				}
+
+				return $this->cache->get('signature');
 
 			// Creation Time is in the MOOV/MVHD atom
 			case 'creation_date':
@@ -74,6 +81,7 @@ class QuickTime extends Base {
 
 				return $atom->{$key};
 
+			case 'fh':
 			case 'type':
 				return parent::__get($key);
 

app/Media/QuickTime/Atom.php

@@ -15,7 +15,6 @@ abstract class Atom extends QuickTime
 	protected int $size;
 	protected string $filename;
 
-	protected Collection $cache;
 	protected Collection $atoms;
 
 	public function __construct(int $offset,int $size,string $filename)
@@ -49,11 +48,13 @@ abstract class Atom extends QuickTime
 			case 'width':
 				$atom = $this->find_atoms(trak::class);
 
-				return $atom->map(fn($item)=>$item->{$key})->filter()->max();
+				return $atom->map(fn($item)=>$item->{$key})
+					->filter()
+					->max();
 
-			// Signatures are calculated by the sha of the MDAT atom.
-			case 'signature':
-				return $this->signature();
+			// We need to pass our file handle requests to our parent
+			case 'fh':
+				return parent::__get($key);
 
 			default:
 				throw new \Exception('Unknown key: '.$key);

app/Media/QuickTime/Atoms/mdat.php

@@ -15,22 +15,26 @@ class mdat extends Atom
 	 * Calculate the signature of the data
 	 *
 	 * @param string $alg
-	 * @return string
+	 * @param mixed|null $hash If the hash was initialised already, this is it
+	 * @param bool $next If the final hash is calculated by the calling method
+	 * @return string|\HashContext
 	 */
-	public function signature(string $alg='sha1'): string
+	public function signature(string $alg='sha1',mixed $hash=NULL,bool $next=FALSE): string|\HashContext
 	{
 		if (! Arr::has($this->cache,'signature')) {
 			if ($this->size) {
 				$this->fopen();
 
-				$hash = hash_init($alg);
-
-				while (!is_null($read = $this->fread(16384)))
-					hash_update($hash, $read);
+				$hash = $hash ?: hash_init($alg);
+				while (! is_null($read=$this->fread(16384)))
+					hash_update($hash,$read);
 
 				$this->fclose();
 
-				$this->cache['signature'] = hash_final($hash);
+				if ($next)
+					return $hash;
+				else
+					$this->cache['signature'] = hash_final($hash);
 
 			} else {
 				$this->cache['signature'] = NULL;