Spaces:

Reoo88
/

Prayer-Time-Bot

Running

relay-v2.40-avfill-splice: apply On-validated A/V fill splice fix fleet-wide

a9631e4 verified 19 days ago

20.3 kB

#!/usr/bin/env python3
"""Deterministic decoder-record/reconnect tests; no network or transcoding."""
import json
import os
import pathlib
import shutil
import subprocess
import sys
import tempfile

ROOT=pathlib.Path(sys.argv[1] if len(sys.argv)>1 else pathlib.Path(__file__).parent).resolve()
sys.path.insert(0,str(ROOT))
from flv_bridge import FLVBridge  # noqa: E402
from stream_monitor import StreamMonitor, video_dimensions  # noqa: E402

passed=failed=0
def check(name,ok,detail=''):
    global passed,failed
    if ok:
        passed+=1;print('PASS ',name)
    else:
        failed+=1;print('FAIL ',name,detail)

def tag(kind,ts,body):
    size=len(body)
    header=bytes([kind])+size.to_bytes(3,'big')+bytes([
        (ts>>16)&255,(ts>>8)&255,ts&255,(ts>>24)&255,0,0,0])
    return header+body+(11+size).to_bytes(4,'big')

def flv(*records):
    return b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+b''.join(records)

def parse(blob):
    assert blob[:3]==b'FLV'
    offset=int.from_bytes(blob[5:9],'big')+4;out=[]
    while offset+15<=len(blob):
        header=blob[offset:offset+11];size=int.from_bytes(header[1:4],'big')
        total=11+size+4
        assert offset+total<=len(blob)
        body=blob[offset+11:offset+11+size]
        assert int.from_bytes(blob[offset+11+size:offset+total],'big')==11+size
        ts=(header[7]<<24)|(header[4]<<16)|(header[5]<<8)|header[6]
        out.append((header[0]&31,ts,body));offset+=total
    assert offset==len(blob)
    return out

def chunked(bridge,data):
    cuts=(1,2,7,3,19,5,31,11);out=[];pos=0;i=0
    while pos<len(data):
        n=cuts[i%len(cuts)];out.append(bridge.feed(data[pos:pos+n]));pos+=n;i+=1
    return b''.join(out)

def seq(codec,cfg,legacy=True,frame=1):
    if legacy:
        codec_id=7 if codec=='avc1' else 12
        return bytes([(frame<<4)|codec_id,0,0,0,0])+cfg
    return bytes([0x80|(frame<<4)])+codec.encode()+cfg

def coded(codec,payload,cts=b'\x00\x00\x00',legacy=True,frame=2):
    if legacy:
        codec_id=7 if codec=='avc1' else 12
        return bytes([(frame<<4)|codec_id,1])+cts+payload
    return bytes([0x80|(frame<<4)|1])+codec.encode()+cts+payload

AVC_A=bytes.fromhex('0142c00dffe100166742c00dda0507ec0440000003004000000ca3c50aa801000468ce0fc8')
AVC_B=bytes.fromhex('0142c01effe100196742c01eda0280bfe5c044000003000400000300ca3c58ba8001000468ce0fc8')
HEVC_A=bytes.fromhex('0101600000009000000000003cf000fcfdf8f800000f03200001001840010c01ffff01600000030090000003000003003c959409210001002a42010101600000030090000003000003003ca00a080f16595952930bc05a02000003000200000300321022000100064401c073c189')
HEVC_B=bytes.fromhex('0101600000009000000000003ff000fcfdf8f800000f03200001001840010c01ffff01600000030090000003000003003f959409210001002b42010101600000030090000003000003003fa005020171f2e595952930bc05a0200000030020000003032122000100064401c073c189')
VIDEO_A=b'\x00\x00\x00\x03\x65\x88\x84'
VIDEO_H=b'\x00\x00\x00\x04\x26\x01\xaf\x09'

# A changed AVCDecoderConfigurationRecord must precede its dependent frame and must not raise,
# even when an old caller still enables detect_format_change.
events=[]
b=FLVBridge(detect_format_change=True,allow_raise=lambda:True,user='alice',
            event_logger=lambda user,event,details:events.append((user,event,details)))
avc_input=flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,b'\xff\xff\xfe')),
              tag(9,40,seq('avc1',AVC_B)),tag(9,40,coded('avc1',VIDEO_A)),
              tag(9,80,coded('avc1',VIDEO_A,frame=1)))
avc_out=chunked(b,avc_input);avc_tags=parse(avc_out)
check('AVC configuration replacement stays in one bridge session',b.format_changes==1)
check('AVC replacement is not classified as a codec switch',b.codec_changes==0 and b.video_codec=='avc1')
check('both AVC configuration records are emitted in order',
      [x[2][5:] for x in avc_tags if x[0]==9 and x[2][1:2]==b'\x00']==[AVC_A,AVC_B])
check('AVC coded bytes and signed CTS pass unchanged',
      [x[2] for x in avc_tags if x[0]==9 and x[2][1:2]==b'\x01']==
      [coded('avc1',VIDEO_A,b'\xff\xff\xfe'),coded('avc1',VIDEO_A,frame=1)])
check('dependent frame after a changed record is held for a clean keyframe',
      any(x[1]=='KEYFRAME_RESYNC' and x[2].get('dropped_tags')==1 for x in events),str(events))
check('continuous-source DTS is preserved exactly',[x[1] for x in avc_tags]==[0,0,40,80])
check('AVC config and resolution changes are recorded with broadcaster identity',
      [x[1] for x in events]==['STREAM_CONFIG','DECODER_CONFIG_CHANGE','RESOLUTION_CHANGE','KEYFRAME_RESYNC'] and
      events[2][0]=='alice' and events[2][2]['new_width']==640)

# A complete avcC may itself contain accumulated arrays. Preserve the record as a unit rather
# than trying to append old records with potentially conflicting parameter-set IDs.
sps=(b'\x67\x64\x00\x1f\xac',b'\x67\x64\x00\x1f\xad')
pps=(b'\x68\xee\x3c\x80',b'\x68\xee\x3c\x81')
MULTI_AVC=b'\x01\x64\x00\x1f\xff\xe2'+b''.join(len(x).to_bytes(2,'big')+x for x in sps)+b'\x02'+b''.join(len(x).to_bytes(2,'big')+x for x in pps)
multi=parse(FLVBridge().feed(flv(tag(9,0,seq('avc1',MULTI_AVC)))))
check('multi-SPS/PPS AVC record is preserved whole',multi[0][2][5:]==MULTI_AVC)

# TikTok's legacy HEVC convention is translated tag-for-tag to Enhanced RTMP hvc1.
bh=FLVBridge(detect_format_change=True)
h_in=flv(tag(9,0,seq('hvc1',HEVC_A)),
         tag(9,1,coded('hvc1',VIDEO_H,b'\xff\xff\xfd',frame=2)),
         tag(9,40,seq('hvc1',HEVC_B)),tag(9,41,coded('hvc1',VIDEO_H,frame=1)))
h_out=chunked(bh,h_in);h_tags=parse(h_out)
check('legacy HEVC records are monitored without interruption',bh.format_changes==1 and bh.codec_changes==0)
check('legacy HEVC SequenceStart becomes Enhanced RTMP hvc1',
      [x[2] for x in h_tags if x[0]==9 and (x[2][0]&15)==0]==[b'\x90hvc1'+HEVC_A,b'\x90hvc1'+HEVC_B])
check('legacy HEVC coded payload and CTS are byte-identical after envelope rewrite',
      [x[2] for x in h_tags if x[0]==9 and (x[2][0]&15)==1]==
      [b'\xa1hvc1\xff\xff\xfd'+VIDEO_H,b'\x91hvc1\x00\x00\x00'+VIDEO_H])
check('all legacy HEVC video tags were converted',bh.converted_tags==4)

# Already-enhanced hvc1 must not be rewritten at all.
eh_seq=seq('hvc1',HEVC_A,legacy=False);eh_frame=coded('hvc1',VIDEO_H,b'\x00\x00\x07',legacy=False)
eh=parse(FLVBridge().feed(flv(tag(9,0,eh_seq),tag(9,1,eh_frame))))
check('already-enhanced hvc1 bodies pass unchanged',[x[2] for x in eh]==[eh_seq,eh_frame])

# Reattach suppresses only an identical startup record and preserves timestamp continuity.
reconnect_events=[]
br=FLVBridge(user='alice',event_logger=lambda user,event,details:reconnect_events.append((event,details)))
first=br.feed(flv(tag(9,100,seq('avc1',AVC_A)),tag(9,140,coded('avc1',VIDEO_A))))
last=br.last_out_ts;br.reconnect()
second=br.feed(flv(tag(18,0,b'metadata'),tag(9,0,seq('avc1',AVC_A)),tag(9,40,coded('avc1',VIDEO_A,frame=1))))
joined=parse(first+second)
check('reattach drops second FLV header and startup metadata',len(second)>0 and not second.startswith(b'FLV') and all(x[0]!=18 for x in joined))
check('source reattach is recorded without claiming RTMP closure',
      any(e[0]=='RECONNECT' and e[1]['outbound_rtmp_reused'] is True for e in reconnect_events))
check('reattach drops only identical startup decoder record',sum(1 for x in joined if x[0]==9 and x[2][1:2]==b'\x00')==1)
check('reattach shifts DTS once while preserving valid equal timestamps',
      br.last_out_ts>last and all(a[1]<=z[1] for a,z in zip(joined,joined[1:])))

bc=FLVBridge();part1=bc.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,20,coded('avc1',VIDEO_A))))
bc.reconnect();part2=bc.feed(flv(tag(9,0,seq('avc1',AVC_B)),tag(9,20,coded('avc1',VIDEO_A))))
changed=parse(part1+part2)
check('reattach never suppresses a changed decoder record',
      [x[2][5:] for x in changed if x[0]==9 and x[2][1:2]==b'\x00']==[AVC_A,AVC_B])
check('changed reattach remains on one FLV byte stream',not part2.startswith(b'FLV') and bc.format_changes==1)

# A sequence header stamped 0 must not consume the splice bias: the first real
# frame of a refreshed TikTok FLV can carry a far-away room DTS, and letting a
# ts=0 header set the bias makes that frame leap millions of ms into the future
# (the output timeline collapses and YouTube discards the leg as noData).
bh0=FLVBridge(user='alice',event_logger=lambda *a:None)
bh0.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
             tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
bh0.freeze_span_bytes(2000);bh0.reconnect()
out_h0=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bh0.feed(flv(
    tag(9,0,seq('avc1',AVC_B)),tag(9,500000,coded('avc1',VIDEO_A,frame=1)),
    tag(9,500040,coded('avc1',VIDEO_H,frame=2)))))
check('ts=0 changed video header does not consume splice bias',
      [t[1] for t in out_h0]==[3080,3120,3160],str([t[1] for t in out_h0]))
ba0=FLVBridge(user='alice',event_logger=lambda *a:None)
ba0.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
             tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
ba0.freeze_span_bytes(2000);ba0.reconnect()
out_a0=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+ba0.feed(flv(
    tag(8,0,b'\xaf\x00\x12\x10'),tag(9,0,seq('avc1',AVC_A)),
    tag(9,500000,coded('avc1',VIDEO_A,frame=1)))))
check('ts=0 audio header does not consume splice bias',
      [t[1] for t in out_a0]==[3080,3120],str([t[1] for t in out_a0]))

# The byte bridge can represent a FourCC transition without raising or closing. FFmpeg 7 creates
# a new late AVStream for such a transition, so production source selection still pins one codec;
# same-codec decoder-record replacement above is the fully verified path.
switch_events=[]
bs=FLVBridge(detect_format_change=True,user='alice',
             event_logger=lambda user,event,details:switch_events.append(event))
switch=bs.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,1,coded('avc1',VIDEO_A)),
                   tag(9,40,seq('hvc1',HEVC_A,legacy=False)),tag(9,41,coded('hvc1',VIDEO_H,legacy=False))))
switch_tags=parse(switch)
check('AVC to HEVC transition holds dependents for a keyframe without raising',len(switch_tags)==3)
check('codec transition is separately observable',bs.format_changes==1 and bs.codec_changes==1 and bs.video_codec=='hvc1')
check('codec transition writes CODEC_CHANGE without stopping the bridge','CODEC_CHANGE' in switch_events)

try:
    FLVBridge().feed(flv(tag(9,0,b'\x90hvc1')))
    truncated=False
except ValueError:
    truncated=True
check('truncated Enhanced SequenceStart fails in a controlled way',truncated)

# Metric transitions are inferred from tag bytes/timestamps, never by decoding the picture.
metric_events=[];records=[tag(9,0,seq('avc1',AVC_A))]
for ts in range(0,10000,40):
    frame=1 if ts in (0,2000,4000,5000,6000,7000,8000,9000) else 2
    payload=(b'x'*100) if ts<5000 else (b'y'*1000)
    records.append(tag(9,ts,coded('avc1',payload,frame=frame)))
FLVBridge(user='alice',event_logger=lambda user,event,details:metric_events.append(event)).feed(flv(*records))
check('byte-level monitor detects a sudden bitrate change','BITRATE_CHANGE' in metric_events)
check('byte-level monitor detects a keyframe-interval change','KEYFRAME_CHANGE' in metric_events)
check('AVC and HEVC SPS dimensions are parsed without decoding',
      video_dimensions('avc1',AVC_A)==(320,240) and video_dimensions('avc1',AVC_B)==(640,360) and
      video_dimensions('hvc1',HEVC_A)==(320,240) and video_dimensions('hvc1',HEVC_B)==(640,360))

with tempfile.TemporaryDirectory() as mon_dir:
    mon_path=pathlib.Path(mon_dir)/'logs'/'stream_events.json';mon=StreamMonitor(mon_path)
    mon.log('alice','CONNECTION_ERROR',{'scope':'youtube_rtmp','url':'secret-url',
            'stream_key':'secret-key','reason':'failed https://secret-host/live/SECRET'})
    mon.note_rtmp_open('alice');mon.note_rtmp_open('alice',{'mode':'copy'})
    saved=json.loads(mon_path.read_text())
    check('stream event file is valid JSON with the required schema',
          len(saved)==2 and all(set(('timestamp','broadcaster','event','details'))<=set(x) for x in saved))
    check('stream monitor never persists URLs, keys or tokens',
          all(x not in mon_path.read_text() for x in ('secret-url','secret-key','secret-host','SECRET')))
    check('stream event file is owner-only',mon_path.stat().st_mode&0o777==0o600)
    check('second outbound publisher open is recorded as RECONNECT',saved[-1]['event']=='RECONNECT')

# FFmpeg 7 is the real outbound middle layer. If available, prove its FLV demux/mux pair writes
# replacement AVC and HEVC configuration records instead of fixing extradata at startup.
ff=os.environ.get('FFMPEG_PATH') or shutil.which('ffmpeg')
if ff and pathlib.Path(ff).is_file():
    with tempfile.TemporaryDirectory() as td:
        td=pathlib.Path(td)
        fixtures=(
            ('avc',flv(tag(9,0,seq('avc1',AVC_A)),tag(9,1,coded('avc1',VIDEO_A,frame=1)),
                       tag(9,40,seq('avc1',AVC_B)),tag(9,41,coded('avc1',VIDEO_A,frame=1))),[AVC_A,AVC_B]),
            ('hevc',flv(tag(9,0,seq('hvc1',HEVC_A,legacy=False)),tag(9,1,coded('hvc1',VIDEO_H,legacy=False,frame=1)),
                        tag(9,40,seq('hvc1',HEVC_B,legacy=False)),tag(9,41,coded('hvc1',VIDEO_H,legacy=False,frame=1))),[HEVC_A,HEVC_B]),
        )
        for name,data,expected in fixtures:
            src=td/(name+'.flv');dst=td/(name+'-out.flv');src.write_bytes(data)
            run=subprocess.run([ff,'-y','-hide_banner','-loglevel','error','-i',str(src),
                '-map','0:v:0','-c:v','copy','-flvflags','no_duration_filesize','-f','flv',str(dst)],
                stdout=subprocess.PIPE,stderr=subprocess.PIPE,timeout=20)
            bodies=[x[2] for x in parse(dst.read_bytes()) if x[0]==9] if run.returncode==0 and dst.exists() else []
            configs=[]
            for body in bodies:
                if body[0]&0x80 and (body[0]&15)==0:configs.append(body[5:])
                elif len(body)>5 and (body[0]&15)==7 and body[1]==0:configs.append(body[5:])
            check('FFmpeg copy re-emits both %s decoder records'%name,run.returncode==0 and configs==expected,
                  run.stderr.decode(errors='replace')[-300:])
            units=[]
            for body in bodies:
                if name=='avc' and len(body)>5 and not(body[0]&0x80) and body[1]==1:
                    units.append(body[5:])
                elif name=='hevc' and len(body)>5 and body[0]&0x80:
                    if (body[0]&15)==1 and len(body)>=8:units.append(body[8:])
                    elif (body[0]&15)==3:units.append(body[5:])
            payload=VIDEO_A if name=='avc' else VIDEO_H
            check('FFmpeg copy preserves %s encoded access units byte-for-byte'%name,units==[payload,payload])
else:
    print('SKIP  FFmpeg decoder-record remux checks (ffmpeg unavailable)')

# --- Keyframe gate: splices/config changes resume only on a clean IDR, so the
# viewer sees the held picture instead of gray/colour-static error concealment ---
gev=[];bg=FLVBridge(user='alice',event_logger=lambda user,event,details:gev.append((event,details)))
bg.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,frame=1)),
            tag(9,40,coded('avc1',VIDEO_H,frame=2))))
bg.reconnect()
seg2=flv(tag(9,100,seq('avc1',AVC_A)),tag(9,100,coded('avc1',VIDEO_H,frame=2)),
         tag(8,120,b'\xaf\x01\x11\x22'),
         tag(9,140,coded('avc1',VIDEO_H,frame=2)),tag(9,180,coded('avc1',VIDEO_A,frame=1)),
         tag(9,220,coded('avc1',VIDEO_H,frame=2)))
out_g=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bg.feed(seg2))
check('post-reconnect inter frames are held until a keyframe',
      [t[2] for t in out_g if t[0]==9]==[coded('avc1',VIDEO_A,frame=1),coded('avc1',VIDEO_H,frame=2)],
      str(out_g))
check('audio flows while the video gate is closed',any(t[0]==8 for t in out_g),str(out_g))
check('keyframe resync is recorded with the dropped count',
      ('KEYFRAME_RESYNC',{'dropped_tags':2,'capped':False}) in gev,str(gev))
gev2=[];bg2=FLVBridge(user='alice',event_logger=lambda u,e,d:gev2.append((e,d)))
bg2.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,frame=1))))
out_c=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bg2.feed(
    tag(9,40,seq('avc1',AVC_B))+tag(9,40,coded('avc1',VIDEO_H,frame=2))+
    tag(9,80,coded('avc1',VIDEO_A,frame=1))))
check('config change holds dependents until the next keyframe',
      [t[2] for t in out_c if t[0]==9]==[seq('avc1',AVC_B),coded('avc1',VIDEO_A,frame=1)],str(out_c))

# --- Gap filler: frozen keyframes keep the timeline (and YouTube leg) alive ---
b2=FLVBridge(user='alice',event_logger=lambda *a:None)
check('no filler before any keyframe was emitted',b2.freeze_bytes() is None)
src=flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
        tag(9,1040,coded('avc1',VIDEO_H,frame=2)),tag(8,1040,b'\xaf\x01\x11\x22'))
out2=b2.feed(src)
f1=b2.freeze_bytes();f2=b2.freeze_bytes()
ftags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+f1+f2)
check('filler repeats the last keyframe body untouched',
      [t[2] for t in ftags]==[coded('avc1',VIDEO_A,frame=1)]*2, str(ftags))
check('filler timestamps advance monotonically by the step',
      [t[1] for t in ftags]==[3040,5040], str([t[1] for t in ftags]))
# Real source resumes after filling on the same connection: output must continue
# from the filler-advanced clock, never backwards into a corrupted timeline.
resumed=b2.feed(tag(9,1080,coded('avc1',VIDEO_H,frame=2)))
rtags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+resumed)
check('resumed source is spliced after the filler clock',
      rtags and rtags[0][1]>=5040, str(rtags))
check('filler does not rewrite the resumed frame body',
      rtags and rtags[0][2]==coded('avc1',VIDEO_H,frame=2))

# --- A/V gap filler: silent AAC spans keep the audio leg alive too ---
HE_ASC=bytes.fromhex('131056e598');SIL_STEREO=b'\xaf\x01'+bytes.fromhex('211004608c1c')
b3=FLVBridge(user='alice',event_logger=lambda *a:None)
b3.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(8,1000,b'\xaf\x00'+HE_ASC),
            tag(9,1000,coded('avc1',VIDEO_A,frame=1)),tag(8,1042,b'\xaf\x01\x54\x54'),
            tag(9,1080,coded('avc1',VIDEO_H,frame=2))))
check('bridge learns the HE-AAC source config',b3.fill_audio_ready() and b3.audio_he)
span1=b3.freeze_span_bytes(2000);span2=b3.freeze_span_bytes(2000)
stags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+span1+span2)
aud=[t for t in stags if t[0]==8];vid=[t for t in stags if t[0]==9]
check('HE fill first re-declares plain LC at the output rate',
      aud and aud[0][2]==b'\xaf\x00\x11\x90',str(aud[:1]))
frames=[t for t in aud if t[2]==SIL_STEREO]
check('silent AAC frames fill both spans at 1024-sample cadence',
      184<=len(frames)<=190,str(len(frames)))
diffs=[b-a for a,b in zip([t[1] for t in frames],[t[1] for t in frames[1:]])]
check('silent frame timestamps step ~21.3ms (48kHz output rate)',
      diffs and all(d in (21,22) for d in diffs),str(diffs[:6]))
check('each fill span still ends on the frozen keyframe',
      [t[1] for t in vid]==[3080,5080],str([t[1] for t in vid]))
back=b3.feed(tag(8,1100,b'\xaf\x01\x54\x54'))
btags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+back)
check('first real frame after an LC fill is preceded by the source HE header',
      len(btags)==2 and btags[0][2]==b'\xaf\x00'+HE_ASC and btags[1][2]==b'\xaf\x01\x54\x54',
      str(btags))
check('restored header keeps the spliced timeline',btags and btags[0][1]==btags[1][1]>=5080,str(btags))
# Pure-LC source: silent frames ride under the original header, no switching.
b4=FLVBridge(user='alice',event_logger=lambda *a:None)
b4.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(8,1000,b'\xaf\x00\x12\x10'),
            tag(9,1000,coded('avc1',VIDEO_A,frame=1)),tag(8,1023,b'\xaf\x01\x54\x54'),
            tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
span=b4.freeze_span_bytes(2000)
ltags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+span)
laud=[t for t in ltags if t[0]==8]
check('LC fill emits no replacement header',
      laud and all(t[2]==SIL_STEREO for t in laud),str(laud[:2]))
ldiffs=[b-a for a,b in zip([t[1] for t in laud],[t[1] for t in laud[1:]])]
check('LC silent cadence is ~23.2ms (44.1kHz)',ldiffs and all(d in (23,24) for d in ldiffs),str(ldiffs[:6]))

print('\n%d passed, %d failed'%(passed,failed))
sys.exit(1 if failed else 0)

	#!/usr/bin/env python3
	"""Deterministic decoder-record/reconnect tests; no network or transcoding."""
	import json
	import os
	import pathlib
	import shutil
	import subprocess
	import sys
	import tempfile

	ROOT=pathlib.Path(sys.argv[1] if len(sys.argv)>1 else pathlib.Path(__file__).parent).resolve()
	sys.path.insert(0,str(ROOT))
	from flv_bridge import FLVBridge # noqa: E402
	from stream_monitor import StreamMonitor, video_dimensions # noqa: E402

	passed=failed=0
	def check(name,ok,detail=''):
	global passed,failed
	if ok:
	passed+=1;print('PASS ',name)
	else:
	failed+=1;print('FAIL ',name,detail)

	def tag(kind,ts,body):
	size=len(body)
	header=bytes([kind])+size.to_bytes(3,'big')+bytes([
	(ts>>16)&255,(ts>>8)&255,ts&255,(ts>>24)&255,0,0,0])
	return header+body+(11+size).to_bytes(4,'big')

	def flv(*records):
	return b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+b''.join(records)

	def parse(blob):
	assert blob[:3]==b'FLV'
	offset=int.from_bytes(blob[5:9],'big')+4;out=[]
	while offset+15<=len(blob):
	header=blob[offset:offset+11];size=int.from_bytes(header[1:4],'big')
	total=11+size+4
	assert offset+total<=len(blob)
	body=blob[offset+11:offset+11+size]
	assert int.from_bytes(blob[offset+11+size:offset+total],'big')==11+size
	ts=(header[7]<<24)\|(header[4]<<16)\|(header[5]<<8)\|header[6]
	out.append((header[0]&31,ts,body));offset+=total
	assert offset==len(blob)
	return out

	def chunked(bridge,data):
	cuts=(1,2,7,3,19,5,31,11);out=[];pos=0;i=0
	while pos<len(data):
	n=cuts[i%len(cuts)];out.append(bridge.feed(data[pos:pos+n]));pos+=n;i+=1
	return b''.join(out)

	def seq(codec,cfg,legacy=True,frame=1):
	if legacy:
	codec_id=7 if codec=='avc1' else 12
	return bytes([(frame<<4)\|codec_id,0,0,0,0])+cfg
	return bytes([0x80\|(frame<<4)])+codec.encode()+cfg

	def coded(codec,payload,cts=b'\x00\x00\x00',legacy=True,frame=2):
	if legacy:
	codec_id=7 if codec=='avc1' else 12
	return bytes([(frame<<4)\|codec_id,1])+cts+payload
	return bytes([0x80\|(frame<<4)\|1])+codec.encode()+cts+payload

	AVC_A=bytes.fromhex('0142c00dffe100166742c00dda0507ec0440000003004000000ca3c50aa801000468ce0fc8')
	AVC_B=bytes.fromhex('0142c01effe100196742c01eda0280bfe5c044000003000400000300ca3c58ba8001000468ce0fc8')
	HEVC_A=bytes.fromhex('0101600000009000000000003cf000fcfdf8f800000f03200001001840010c01ffff01600000030090000003000003003c959409210001002a42010101600000030090000003000003003ca00a080f16595952930bc05a02000003000200000300321022000100064401c073c189')
	HEVC_B=bytes.fromhex('0101600000009000000000003ff000fcfdf8f800000f03200001001840010c01ffff01600000030090000003000003003f959409210001002b42010101600000030090000003000003003fa005020171f2e595952930bc05a0200000030020000003032122000100064401c073c189')
	VIDEO_A=b'\x00\x00\x00\x03\x65\x88\x84'
	VIDEO_H=b'\x00\x00\x00\x04\x26\x01\xaf\x09'

	# A changed AVCDecoderConfigurationRecord must precede its dependent frame and must not raise,
	# even when an old caller still enables detect_format_change.
	events=[]
	b=FLVBridge(detect_format_change=True,allow_raise=lambda:True,user='alice',
	event_logger=lambda user,event,details:events.append((user,event,details)))
	avc_input=flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,b'\xff\xff\xfe')),
	tag(9,40,seq('avc1',AVC_B)),tag(9,40,coded('avc1',VIDEO_A)),
	tag(9,80,coded('avc1',VIDEO_A,frame=1)))
	avc_out=chunked(b,avc_input);avc_tags=parse(avc_out)
	check('AVC configuration replacement stays in one bridge session',b.format_changes==1)
	check('AVC replacement is not classified as a codec switch',b.codec_changes==0 and b.video_codec=='avc1')
	check('both AVC configuration records are emitted in order',
	[x[2][5:] for x in avc_tags if x[0]==9 and x[2][1:2]==b'\x00']==[AVC_A,AVC_B])
	check('AVC coded bytes and signed CTS pass unchanged',
	[x[2] for x in avc_tags if x[0]==9 and x[2][1:2]==b'\x01']==
	[coded('avc1',VIDEO_A,b'\xff\xff\xfe'),coded('avc1',VIDEO_A,frame=1)])
	check('dependent frame after a changed record is held for a clean keyframe',
	any(x[1]=='KEYFRAME_RESYNC' and x[2].get('dropped_tags')==1 for x in events),str(events))
	check('continuous-source DTS is preserved exactly',[x[1] for x in avc_tags]==[0,0,40,80])
	check('AVC config and resolution changes are recorded with broadcaster identity',
	[x[1] for x in events]==['STREAM_CONFIG','DECODER_CONFIG_CHANGE','RESOLUTION_CHANGE','KEYFRAME_RESYNC'] and
	events[2][0]=='alice' and events[2][2]['new_width']==640)

	# A complete avcC may itself contain accumulated arrays. Preserve the record as a unit rather
	# than trying to append old records with potentially conflicting parameter-set IDs.
	sps=(b'\x67\x64\x00\x1f\xac',b'\x67\x64\x00\x1f\xad')
	pps=(b'\x68\xee\x3c\x80',b'\x68\xee\x3c\x81')
	MULTI_AVC=b'\x01\x64\x00\x1f\xff\xe2'+b''.join(len(x).to_bytes(2,'big')+x for x in sps)+b'\x02'+b''.join(len(x).to_bytes(2,'big')+x for x in pps)
	multi=parse(FLVBridge().feed(flv(tag(9,0,seq('avc1',MULTI_AVC)))))
	check('multi-SPS/PPS AVC record is preserved whole',multi[0][2][5:]==MULTI_AVC)

	# TikTok's legacy HEVC convention is translated tag-for-tag to Enhanced RTMP hvc1.
	bh=FLVBridge(detect_format_change=True)
	h_in=flv(tag(9,0,seq('hvc1',HEVC_A)),
	tag(9,1,coded('hvc1',VIDEO_H,b'\xff\xff\xfd',frame=2)),
	tag(9,40,seq('hvc1',HEVC_B)),tag(9,41,coded('hvc1',VIDEO_H,frame=1)))
	h_out=chunked(bh,h_in);h_tags=parse(h_out)
	check('legacy HEVC records are monitored without interruption',bh.format_changes==1 and bh.codec_changes==0)
	check('legacy HEVC SequenceStart becomes Enhanced RTMP hvc1',
	[x[2] for x in h_tags if x[0]==9 and (x[2][0]&15)==0]==[b'\x90hvc1'+HEVC_A,b'\x90hvc1'+HEVC_B])
	check('legacy HEVC coded payload and CTS are byte-identical after envelope rewrite',
	[x[2] for x in h_tags if x[0]==9 and (x[2][0]&15)==1]==
	[b'\xa1hvc1\xff\xff\xfd'+VIDEO_H,b'\x91hvc1\x00\x00\x00'+VIDEO_H])
	check('all legacy HEVC video tags were converted',bh.converted_tags==4)

	# Already-enhanced hvc1 must not be rewritten at all.
	eh_seq=seq('hvc1',HEVC_A,legacy=False);eh_frame=coded('hvc1',VIDEO_H,b'\x00\x00\x07',legacy=False)
	eh=parse(FLVBridge().feed(flv(tag(9,0,eh_seq),tag(9,1,eh_frame))))
	check('already-enhanced hvc1 bodies pass unchanged',[x[2] for x in eh]==[eh_seq,eh_frame])

	# Reattach suppresses only an identical startup record and preserves timestamp continuity.
	reconnect_events=[]
	br=FLVBridge(user='alice',event_logger=lambda user,event,details:reconnect_events.append((event,details)))
	first=br.feed(flv(tag(9,100,seq('avc1',AVC_A)),tag(9,140,coded('avc1',VIDEO_A))))
	last=br.last_out_ts;br.reconnect()
	second=br.feed(flv(tag(18,0,b'metadata'),tag(9,0,seq('avc1',AVC_A)),tag(9,40,coded('avc1',VIDEO_A,frame=1))))
	joined=parse(first+second)
	check('reattach drops second FLV header and startup metadata',len(second)>0 and not second.startswith(b'FLV') and all(x[0]!=18 for x in joined))
	check('source reattach is recorded without claiming RTMP closure',
	any(e[0]=='RECONNECT' and e[1]['outbound_rtmp_reused'] is True for e in reconnect_events))
	check('reattach drops only identical startup decoder record',sum(1 for x in joined if x[0]==9 and x[2][1:2]==b'\x00')==1)
	check('reattach shifts DTS once while preserving valid equal timestamps',
	br.last_out_ts>last and all(a[1]<=z[1] for a,z in zip(joined,joined[1:])))

	bc=FLVBridge();part1=bc.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,20,coded('avc1',VIDEO_A))))
	bc.reconnect();part2=bc.feed(flv(tag(9,0,seq('avc1',AVC_B)),tag(9,20,coded('avc1',VIDEO_A))))
	changed=parse(part1+part2)
	check('reattach never suppresses a changed decoder record',
	[x[2][5:] for x in changed if x[0]==9 and x[2][1:2]==b'\x00']==[AVC_A,AVC_B])
	check('changed reattach remains on one FLV byte stream',not part2.startswith(b'FLV') and bc.format_changes==1)

	# A sequence header stamped 0 must not consume the splice bias: the first real
	# frame of a refreshed TikTok FLV can carry a far-away room DTS, and letting a
	# ts=0 header set the bias makes that frame leap millions of ms into the future
	# (the output timeline collapses and YouTube discards the leg as noData).
	bh0=FLVBridge(user='alice',event_logger=lambda *a:None)
	bh0.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
	tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
	bh0.freeze_span_bytes(2000);bh0.reconnect()
	out_h0=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bh0.feed(flv(
	tag(9,0,seq('avc1',AVC_B)),tag(9,500000,coded('avc1',VIDEO_A,frame=1)),
	tag(9,500040,coded('avc1',VIDEO_H,frame=2)))))
	check('ts=0 changed video header does not consume splice bias',
	[t[1] for t in out_h0]==[3080,3120,3160],str([t[1] for t in out_h0]))
	ba0=FLVBridge(user='alice',event_logger=lambda *a:None)
	ba0.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
	tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
	ba0.freeze_span_bytes(2000);ba0.reconnect()
	out_a0=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+ba0.feed(flv(
	tag(8,0,b'\xaf\x00\x12\x10'),tag(9,0,seq('avc1',AVC_A)),
	tag(9,500000,coded('avc1',VIDEO_A,frame=1)))))
	check('ts=0 audio header does not consume splice bias',
	[t[1] for t in out_a0]==[3080,3120],str([t[1] for t in out_a0]))

	# The byte bridge can represent a FourCC transition without raising or closing. FFmpeg 7 creates
	# a new late AVStream for such a transition, so production source selection still pins one codec;
	# same-codec decoder-record replacement above is the fully verified path.
	switch_events=[]
	bs=FLVBridge(detect_format_change=True,user='alice',
	event_logger=lambda user,event,details:switch_events.append(event))
	switch=bs.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,1,coded('avc1',VIDEO_A)),
	tag(9,40,seq('hvc1',HEVC_A,legacy=False)),tag(9,41,coded('hvc1',VIDEO_H,legacy=False))))
	switch_tags=parse(switch)
	check('AVC to HEVC transition holds dependents for a keyframe without raising',len(switch_tags)==3)
	check('codec transition is separately observable',bs.format_changes==1 and bs.codec_changes==1 and bs.video_codec=='hvc1')
	check('codec transition writes CODEC_CHANGE without stopping the bridge','CODEC_CHANGE' in switch_events)

	try:
	FLVBridge().feed(flv(tag(9,0,b'\x90hvc1')))
	truncated=False
	except ValueError:
	truncated=True
	check('truncated Enhanced SequenceStart fails in a controlled way',truncated)

	# Metric transitions are inferred from tag bytes/timestamps, never by decoding the picture.
	metric_events=[];records=[tag(9,0,seq('avc1',AVC_A))]
	for ts in range(0,10000,40):
	frame=1 if ts in (0,2000,4000,5000,6000,7000,8000,9000) else 2
	payload=(b'x'100) if ts<5000 else (b'y'1000)
	records.append(tag(9,ts,coded('avc1',payload,frame=frame)))
	FLVBridge(user='alice',event_logger=lambda user,event,details:metric_events.append(event)).feed(flv(*records))
	check('byte-level monitor detects a sudden bitrate change','BITRATE_CHANGE' in metric_events)
	check('byte-level monitor detects a keyframe-interval change','KEYFRAME_CHANGE' in metric_events)
	check('AVC and HEVC SPS dimensions are parsed without decoding',
	video_dimensions('avc1',AVC_A)==(320,240) and video_dimensions('avc1',AVC_B)==(640,360) and
	video_dimensions('hvc1',HEVC_A)==(320,240) and video_dimensions('hvc1',HEVC_B)==(640,360))

	with tempfile.TemporaryDirectory() as mon_dir:
	mon_path=pathlib.Path(mon_dir)/'logs'/'stream_events.json';mon=StreamMonitor(mon_path)
	mon.log('alice','CONNECTION_ERROR',{'scope':'youtube_rtmp','url':'secret-url',
	'stream_key':'secret-key','reason':'failed https://secret-host/live/SECRET'})
	mon.note_rtmp_open('alice');mon.note_rtmp_open('alice',{'mode':'copy'})
	saved=json.loads(mon_path.read_text())
	check('stream event file is valid JSON with the required schema',
	len(saved)==2 and all(set(('timestamp','broadcaster','event','details'))<=set(x) for x in saved))
	check('stream monitor never persists URLs, keys or tokens',
	all(x not in mon_path.read_text() for x in ('secret-url','secret-key','secret-host','SECRET')))
	check('stream event file is owner-only',mon_path.stat().st_mode&0o777==0o600)
	check('second outbound publisher open is recorded as RECONNECT',saved[-1]['event']=='RECONNECT')

	# FFmpeg 7 is the real outbound middle layer. If available, prove its FLV demux/mux pair writes
	# replacement AVC and HEVC configuration records instead of fixing extradata at startup.
	ff=os.environ.get('FFMPEG_PATH') or shutil.which('ffmpeg')
	if ff and pathlib.Path(ff).is_file():
	with tempfile.TemporaryDirectory() as td:
	td=pathlib.Path(td)
	fixtures=(
	('avc',flv(tag(9,0,seq('avc1',AVC_A)),tag(9,1,coded('avc1',VIDEO_A,frame=1)),
	tag(9,40,seq('avc1',AVC_B)),tag(9,41,coded('avc1',VIDEO_A,frame=1))),[AVC_A,AVC_B]),
	('hevc',flv(tag(9,0,seq('hvc1',HEVC_A,legacy=False)),tag(9,1,coded('hvc1',VIDEO_H,legacy=False,frame=1)),
	tag(9,40,seq('hvc1',HEVC_B,legacy=False)),tag(9,41,coded('hvc1',VIDEO_H,legacy=False,frame=1))),[HEVC_A,HEVC_B]),
	)
	for name,data,expected in fixtures:
	src=td/(name+'.flv');dst=td/(name+'-out.flv');src.write_bytes(data)
	run=subprocess.run([ff,'-y','-hide_banner','-loglevel','error','-i',str(src),
	'-map','0:v:0','-c:v','copy','-flvflags','no_duration_filesize','-f','flv',str(dst)],
	stdout=subprocess.PIPE,stderr=subprocess.PIPE,timeout=20)
	bodies=[x[2] for x in parse(dst.read_bytes()) if x[0]==9] if run.returncode==0 and dst.exists() else []
	configs=[]
	for body in bodies:
	if body[0]&0x80 and (body[0]&15)==0:configs.append(body[5:])
	elif len(body)>5 and (body[0]&15)==7 and body[1]==0:configs.append(body[5:])
	check('FFmpeg copy re-emits both %s decoder records'%name,run.returncode==0 and configs==expected,
	run.stderr.decode(errors='replace')[-300:])
	units=[]
	for body in bodies:
	if name=='avc' and len(body)>5 and not(body[0]&0x80) and body[1]==1:
	units.append(body[5:])
	elif name=='hevc' and len(body)>5 and body[0]&0x80:
	if (body[0]&15)==1 and len(body)>=8:units.append(body[8:])
	elif (body[0]&15)==3:units.append(body[5:])
	payload=VIDEO_A if name=='avc' else VIDEO_H
	check('FFmpeg copy preserves %s encoded access units byte-for-byte'%name,units==[payload,payload])
	else:
	print('SKIP FFmpeg decoder-record remux checks (ffmpeg unavailable)')

	# --- Keyframe gate: splices/config changes resume only on a clean IDR, so the
	# viewer sees the held picture instead of gray/colour-static error concealment ---
	gev=[];bg=FLVBridge(user='alice',event_logger=lambda user,event,details:gev.append((event,details)))
	bg.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,frame=1)),
	tag(9,40,coded('avc1',VIDEO_H,frame=2))))
	bg.reconnect()
	seg2=flv(tag(9,100,seq('avc1',AVC_A)),tag(9,100,coded('avc1',VIDEO_H,frame=2)),
	tag(8,120,b'\xaf\x01\x11\x22'),
	tag(9,140,coded('avc1',VIDEO_H,frame=2)),tag(9,180,coded('avc1',VIDEO_A,frame=1)),
	tag(9,220,coded('avc1',VIDEO_H,frame=2)))
	out_g=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bg.feed(seg2))
	check('post-reconnect inter frames are held until a keyframe',
	[t[2] for t in out_g if t[0]==9]==[coded('avc1',VIDEO_A,frame=1),coded('avc1',VIDEO_H,frame=2)],
	str(out_g))
	check('audio flows while the video gate is closed',any(t[0]==8 for t in out_g),str(out_g))
	check('keyframe resync is recorded with the dropped count',
	('KEYFRAME_RESYNC',{'dropped_tags':2,'capped':False}) in gev,str(gev))
	gev2=[];bg2=FLVBridge(user='alice',event_logger=lambda u,e,d:gev2.append((e,d)))
	bg2.feed(flv(tag(9,0,seq('avc1',AVC_A)),tag(9,0,coded('avc1',VIDEO_A,frame=1))))
	out_c=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+bg2.feed(
	tag(9,40,seq('avc1',AVC_B))+tag(9,40,coded('avc1',VIDEO_H,frame=2))+
	tag(9,80,coded('avc1',VIDEO_A,frame=1))))
	check('config change holds dependents until the next keyframe',
	[t[2] for t in out_c if t[0]==9]==[seq('avc1',AVC_B),coded('avc1',VIDEO_A,frame=1)],str(out_c))

	# --- Gap filler: frozen keyframes keep the timeline (and YouTube leg) alive ---
	b2=FLVBridge(user='alice',event_logger=lambda *a:None)
	check('no filler before any keyframe was emitted',b2.freeze_bytes() is None)
	src=flv(tag(9,1000,seq('avc1',AVC_A)),tag(9,1000,coded('avc1',VIDEO_A,frame=1)),
	tag(9,1040,coded('avc1',VIDEO_H,frame=2)),tag(8,1040,b'\xaf\x01\x11\x22'))
	out2=b2.feed(src)
	f1=b2.freeze_bytes();f2=b2.freeze_bytes()
	ftags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+f1+f2)
	check('filler repeats the last keyframe body untouched',
	[t[2] for t in ftags]==[coded('avc1',VIDEO_A,frame=1)]*2, str(ftags))
	check('filler timestamps advance monotonically by the step',
	[t[1] for t in ftags]==[3040,5040], str([t[1] for t in ftags]))
	# Real source resumes after filling on the same connection: output must continue
	# from the filler-advanced clock, never backwards into a corrupted timeline.
	resumed=b2.feed(tag(9,1080,coded('avc1',VIDEO_H,frame=2)))
	rtags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+resumed)
	check('resumed source is spliced after the filler clock',
	rtags and rtags[0][1]>=5040, str(rtags))
	check('filler does not rewrite the resumed frame body',
	rtags and rtags[0][2]==coded('avc1',VIDEO_H,frame=2))

	# --- A/V gap filler: silent AAC spans keep the audio leg alive too ---
	HE_ASC=bytes.fromhex('131056e598');SIL_STEREO=b'\xaf\x01'+bytes.fromhex('211004608c1c')
	b3=FLVBridge(user='alice',event_logger=lambda *a:None)
	b3.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(8,1000,b'\xaf\x00'+HE_ASC),
	tag(9,1000,coded('avc1',VIDEO_A,frame=1)),tag(8,1042,b'\xaf\x01\x54\x54'),
	tag(9,1080,coded('avc1',VIDEO_H,frame=2))))
	check('bridge learns the HE-AAC source config',b3.fill_audio_ready() and b3.audio_he)
	span1=b3.freeze_span_bytes(2000);span2=b3.freeze_span_bytes(2000)
	stags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+span1+span2)
	aud=[t for t in stags if t[0]==8];vid=[t for t in stags if t[0]==9]
	check('HE fill first re-declares plain LC at the output rate',
	aud and aud[0][2]==b'\xaf\x00\x11\x90',str(aud[:1]))
	frames=[t for t in aud if t[2]==SIL_STEREO]
	check('silent AAC frames fill both spans at 1024-sample cadence',
	184<=len(frames)<=190,str(len(frames)))
	diffs=[b-a for a,b in zip([t[1] for t in frames],[t[1] for t in frames[1:]])]
	check('silent frame timestamps step ~21.3ms (48kHz output rate)',
	diffs and all(d in (21,22) for d in diffs),str(diffs[:6]))
	check('each fill span still ends on the frozen keyframe',
	[t[1] for t in vid]==[3080,5080],str([t[1] for t in vid]))
	back=b3.feed(tag(8,1100,b'\xaf\x01\x54\x54'))
	btags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+back)
	check('first real frame after an LC fill is preceded by the source HE header',
	len(btags)==2 and btags[0][2]==b'\xaf\x00'+HE_ASC and btags[1][2]==b'\xaf\x01\x54\x54',
	str(btags))
	check('restored header keeps the spliced timeline',btags and btags[0][1]==btags[1][1]>=5080,str(btags))
	# Pure-LC source: silent frames ride under the original header, no switching.
	b4=FLVBridge(user='alice',event_logger=lambda *a:None)
	b4.feed(flv(tag(9,1000,seq('avc1',AVC_A)),tag(8,1000,b'\xaf\x00\x12\x10'),
	tag(9,1000,coded('avc1',VIDEO_A,frame=1)),tag(8,1023,b'\xaf\x01\x54\x54'),
	tag(9,1040,coded('avc1',VIDEO_H,frame=2))))
	span=b4.freeze_span_bytes(2000)
	ltags=parse(b'FLV\x01\x05\x00\x00\x00\x09\x00\x00\x00\x00'+span)
	laud=[t for t in ltags if t[0]==8]
	check('LC fill emits no replacement header',
	laud and all(t[2]==SIL_STEREO for t in laud),str(laud[:2]))
	ldiffs=[b-a for a,b in zip([t[1] for t in laud],[t[1] for t in laud[1:]])]
	check('LC silent cadence is ~23.2ms (44.1kHz)',ldiffs and all(d in (23,24) for d in ldiffs),str(ldiffs[:6]))

	print('\n%d passed, %d failed'%(passed,failed))
	sys.exit(1 if failed else 0)