# 本文公开核验脚本：仅验证随附原创文件及声明的有限条件。
import json, csv, hashlib, re, struct, subprocess, sys, zlib
from fractions import Fraction
from pathlib import Path
P = Path(__file__).resolve().parent
def read(name): return json.loads((P/name).read_text(encoding='utf-8-sig'))
def digest(name): return hashlib.sha256((P/name).read_bytes()).hexdigest()
def probe(name, *args):
    command = ['ffprobe','-v','error',*args,'-of','json',str(P/name)]
    run = subprocess.run(command,capture_output=True,text=True,encoding='utf-8',timeout=25)
    assert run.returncode == 0, run.stderr
    return json.loads(run.stdout)
def decode(name):
    command=['ffmpeg','-v','error','-xerror','-i',str(P/name),'-map','0:v?','-map','0:a?','-f','null','-']
    run=subprocess.run(command,capture_output=True,text=True,encoding='utf-8',timeout=25)
    assert run.returncode == 0, run.stderr
    assert not run.stderr.strip(), run.stderr
    return {'file':name,'exit_code':run.returncode,'stderr':run.stderr}
def packets(name, select='v:0'):
    return probe(name,'-select_streams',select,'-show_packets')['packets']
def streams(name): return probe(name,'-show_streams','-show_format')
def stamp(v,base): return Fraction(int(v))*Fraction(base)
def framehash(name):
    run=subprocess.run(['ffmpeg','-v','error','-i',str(P/name),'-map','0:V:0','-f','framemd5','-'],capture_output=True,text=True,encoding='utf-8',timeout=25)
    assert run.returncode==0,run.stderr
    return [x.split(',')[-1].strip() for x in run.stdout.splitlines() if x and not x.startswith('#')]
def emit(value): print(json.dumps(value,ensure_ascii=False,indent=2))

x=streams('offset.mkv');v=packets('offset.mkv','v:0')[0];a=packets('offset.mkv','a:0')[0];delta=Fraction(a['pts_time'])-Fraction(v['pts_time']);assert delta==Fraction(2,5)
emit({'format_start':x['format'].get('start_time'),'stream_starts':[{k:s.get(k) for k in ['index','codec_type','time_base','start_time']} for s in x['streams']],'first_packets':[v,a],'relative_start_seconds':str(delta),'decode':decode('offset.mkv')})