FLV file out of sync

[Gregg]

Hi,

I have a 1GB FLV file shot with an HD webcamera that needs to undergo major cutting.
On my old XP SP2 PC I have Vegas 8 Platinum but it doesn't accept the file. I followed whatever guides I could find here but after demuxed files are imported to Vegas they're already out of sync.
When I open the file with VirtualDub 1.9.11 and start playing it it's also out of sync. It's OK only when I play it in MPC.
Tried to convert to to Xvid without any luck. I updated my K-lite codec pack and ffdshow to the latest versions.
Any help would be appreciated.

[poisondeathray]

Most webcam FLV's will be VFR (variable frame rate) . You can check with flvextract (look at the timecodes), or sometimes mediainfo (view=>text) can give you this information

If it's VFR, you won't be able to edit it and keep in sync, unless you convert it to CFR. This means inserting duplicates where the frame rate drops to keep a constant frame rate. You basically have to screen capture while playing the FLV, and record using a CFR. Most web cams will have very low quality to begin with, so you probably want to record using a lossless format (huge filesizes)

[Gregg]

Hi,

Thanks for your reply.

Below is Mediainfo file:

Format : Flash Video
File size : 1 001 MiB
Duration : 1h 43mn
Overall bit rate : 1 352 Kbps
Encoded date : 2012-05-06 19:15:05
audiodevice : Realtek HD Audio Input
audioinputvolume : 75.000
fmleversion : 3.2.0.9932
presetname : Custom
videodevice : Logitech HD Pro Webcam C910
videokeyframe_frequency : 4.000

Video
Format : VP6
Codec ID : 4
Duration : 1h 43mn
Bit rate : 1 500 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 30.000 fps
Bit depth : 8 bits
Bits/(Pixel*Frame) : 0.054
Stream size : 1.08 GiB

Audio
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 3
Mode : Joint stereo
Mode extension : MS Stereo
Codec ID : 2
Codec ID/Hint : MP3
Duration : 1h 43mn
Bit rate mode : Constant
Bit rate : 192 Kbps
Channel(s) : 2 channels
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 142 MiB (14%)

It looks like both video and audio are constant rate not VRF.

[poisondeathray]

mediainfo isn't always correct, you should look at the timecodes to be sure

But if it is truly CFR then you can import it, either by encoding to a lossless intermediate (e.g. lagarith, ut video codec, huffyuv) , or through a frameserver e.g. through avisynth and avfs

[Gregg]

I don't know what to look for but I guess thy should be evenly spaced or something. This is part of them:

# timecode format v2
0
111
139
171
203
238
268
299
333
365
395
435
462
492
539
571
604
639
668
699
734
768
795
828
861
892
941
972
1003
1036
1068
1102
1133
1165
1196
1227
1268
1293
1340
1371
1404
1437
1467
1499
1533
1563
1597
1630
1659
1691
1739
1771
1809
1837
1867
1900

[poisondeathray]

I don't know what to look for but I guess thy should be evenly spaced or something.

Yes - That's why it's out of sync before you even touch it in vdub, vegas or any NLE, or doing any standard conversion. They assume everything is CFR and disregard this type of timecode information. To keep VFR with a converted file, you mux in the timecodes, but that still means you can't edit it (you're left with the same problem, but a converted file with different compression)

But a media player will obey the timecode information, so it will speed up and slow down the video at various points so it remains in sync with the audio.

[Gregg]

It looks like the only option is to screen capture the video and use the original audio.