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  1. Today I decided to try and solve the FLV to MP4 problems I have. Now I've been at it for hours and feel like giving up. At first I used Google and later only this forum. So far nothing helped.

    At least I came to some conclusions:
    • The converted .mp4 file is in sync if played with VLC or MPC.
    • The sync problem only happens when imported into Sony Vegas Pro 12.
    My complete workflow:
    1. Rip this video from my channel using TwitchTools or TwitchDown. Tried both, same result.
    2. Use ffmpeg to convert the flv to mp4 with this command: "ffmpeg -i Input.flv -c copy -copyts Output.mp4".

    At first I used a .bat file but after seeing some red text flashing by I decided to go straight to the command prompt and see what it was.

    Click image for larger version

Name:	Ffmpeg error.png
Views:	854
Size:	52.0 KB
ID:	24148

    Doesn't tell me much since I'm far from an expert in this area. Here's what I get in MediaInfo:

    Click image for larger version

Name:	Mediainfo.png
Views:	229
Size:	53.0 KB
ID:	24149

    From what I've read there's no automagical way to fix this and I'll have to do it manually. Atm I'm messing around in Vegas to try and see how bad it is. Seems like it's oos in many places. The most prominent place is at 19:20 when we take out a guy. The shots audio are delayed about 1 second. If I put those in place, other areas become out of sync.

    I'm happy to try out ideas and provide you with additional info if you need it.


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  2. Vegas doesn't support VFR (variable frame rates) . This means the framerate speeds up and slows down in sections. Media players like VLC, MPCHC, read the timestamps and speedup/slowdown appropriately, but most NLE's do not

    You can try to convert it to CFR with avisynth and DirectShowSource() with convertfps=true . It attempts to fill in duplicate frames in sections where the FPS drops

    Since the base frame rate is 30

    DirectShowSource("video.flv", fps=30, convertfps=true)

    You would encode to an intermediate which vegas accepts (maybe lossless codec like utvideo, or cineform is near lossless), and I would use uncompressed audio
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  3. Hey!

    Thanks for your swift response. I've never used avisynth and not sure how to apply the code you suggested. Will try it this week and get back to you.
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  4. Member
    Join Date
    Mar 2011
    Search Comp PM
    Originally Posted by Reachground View Post
    Use ffmpeg to convert the flv to mp4 with this command: "ffmpeg -i Input.flv -c copy -copyts Output.mp4".
    I have always used the following, and never had an issue: "ffmpeg -i input.flv -vcodec copy -acodec copy output.mp4"
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