Initiales Halloween-Projekt

tools/check_preview.py

@@ -0,0 +1,35 @@
+"""Inspect MP4 track metadata without external tools."""
+import json, struct, sys
+from pathlib import Path
+
+def boxes(data):
+ offset=0
+ while offset+8<=len(data):
+  size,kind=struct.unpack_from('>I4s',data,offset);header=8
+  if size==1:size=struct.unpack_from('>Q',data,offset+8)[0];header=16
+  if size==0:size=len(data)-offset
+  if size<header or offset+size>len(data):raise ValueError('Invalid MP4 box')
+  yield kind.decode('ascii'), data[offset+header:offset+size]
+  offset+=size
+
+def child(data,name):return next(body for kind,body in boxes(data) if kind==name)
+
+def inspect(path):
+ moov=child(Path(path).read_bytes(),'moov');result=[]
+ for kind,trak in boxes(moov):
+  if kind!='trak':continue
+  mdia=child(trak,'mdia');hdlr=child(mdia,'hdlr');kind=hdlr[8:12].decode()
+  mdhd=child(mdia,'mdhd')
+  if mdhd[0]==0:scale,duration=struct.unpack_from('>II',mdhd,12)
+  else:scale=struct.unpack_from('>I',mdhd,20)[0];duration=struct.unpack_from('>Q',mdhd,24)[0]
+  stbl=child(child(mdia,'minf'),'stbl');stsz=child(stbl,'stsz');count=struct.unpack_from('>I',stsz,8)[0]
+  desc=child(stbl,'stsd');entry=next(boxes(desc[8:]));seconds=duration/scale
+  item={'type':kind,'codec':entry[0],'duration_seconds':seconds,'samples':count}
+  if kind=='vide':
+   width,height=struct.unpack_from('>HH',entry[1],24);item.update(width=width,height=height,fps=count/seconds)
+   assert (width,height,count)==(1280,720,480),item
+   assert abs(seconds-20)<.01,item
+  result.append(item)
+ assert any(t['type']=='soun' for t in result),'Missing audio track'
+ return result
+if __name__=='__main__':print(json.dumps(inspect(sys.argv[1]),indent=2))