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Ask Slashdot: Synchronizing Sound With Video, Using Open Source?

Posted by timothy on from the speed-of-sound-vs-speed-of-light dept.

An anonymous reader writes: I have a decent video camera, but it lacks a terminal for using an external mic. However, I have a comparatively good audio recorder. What I'd like to do is "automagically" synchronize sound recorded on the audio recorder with video taken on the video camera, using Free / Open Source software on Linux, so I can dump in the files from each, hit "Go," and in the end I get my video, synched with the separately recorded audio, in some sane file format. This seems simple, but maybe it isn't: the 800-pound gorilla in the room is PluralEyes, which evidently lots of people pay $200 for --and which doesn't have a Linux version. Partly this is that I'm cheap, partly it's that I like open source software for being open source, and partly it's that I already use Linux as my usual desktop, and resent needing to switch OS to do what seems intuitively to be a simple task. (It seems like something VLC would do, considering its Swiss-Army-Knife approach, but after pulling down all the menus I could find, I don't think that's the case.) I don't see this feature in any of the Open Source video editing programs, so as a fallback question for anyone who's using LiVES, KDEnlive, or other free/Free option, do you have a useful workflow for synching up externally recorded sound? I'd be happy even to find a simple solution that's merely gratis rather than Free, as long as it runs on Ubuntu.

8 of 103 comments (clear)

  1. A Clapboard by Anonymous Coward · · Score: 4, Informative

    What you want is a simple Hollywood style clapboard. Use any two track + video editor and visually line up the audio spike to the video frame where the board is closed.

    1. Re:A Clapboard by cayenne8 · · Score: 4, Informative
      Yep, the good old fashioned way of doing this is looking for the "CLAP" on the waveform and lining it up with the video.

      However, if you want something very polshed and fancy and automatic....take a look at Davinci Resolve 12 Beta.

      This is the free version that contains about 98% of the $1K paid version...what's missing likely you won't miss either....it is now a full blow NLE that compete with Premier and FCPX and others...

      You can do some amazing sync'ing of multi-clip video and sound with this thing..take a look at the demos on site.

      Unfortunatley, the Linux version is only available for Paid version, but hell, who doesn't have a mac or windows box laying around? I mean, if you have money for a decent video set up, you've already poured out some decent cash (camera, lights, software....hell, lenses ALONE)....surely you have laying around a win/osx box or can buy one.

      But, do give Davinci Resolve 12 a look...they also have out Fusion, which is IMHO, going to be a competitor to Adobe After Effects too for SPFX....worth looking into too.

      --
      Light travels faster than sound. This is why some people appear bright until you hear them speak.........
  2. Clap Clap Clap by lars3232 · · Score: 4, Informative

    That is what the movie claps you see in documentaries are for. You produce a clap with your hand, resulting in a spike in your external mic and in the video cameras mic. That way, you know where to sync the two in your favorite video editing tool and you're fine. No need for special software or something similar.

  3. Open Broadcaster Software by JohnnyComeLately · · Score: 4, Informative

    Your issue is very similar to what Twitch streamers go through with delay between audio and video. I'd suggest checking out OBS and there are quite a few how-to videos on YouTube to show you how to sync.

  4. Sync to the audio by linuxwrangler · · Score: 5, Informative

    Don't sync to the video, sync to the audio. Your video recorder records the audio "reference" track and you just sync your externally recorded audio to the reference track. Kdenlive has this feature. Other editors may a well.

    --

    ~~~~~~~
    "You are not remembered for doing what is expected of you." - Atul Chitnis
    1. Re:Sync to the audio by Fone626 · · Score: 5, Informative

      The above is totally correct, I use a separate recorder all the time so that I get better quality audio than my video recorder will supply, and then use Kdenlive to align the audio to the camera's reference audio.

      I've actually made a video that includes how to do it (among other features), and the video itself uses the Align Audio to Reference feature:
      https://www.youtube.com/watch?v=eIO73t228k0

      Here's a short text version:
      https://userbase.kde.org/Kdenlive/Manual/Timeline/Right_Click_Menu

  5. mencoder by carlhaagen · · Score: 4, Informative

    mencoder will do exactly what you need, muxing separate video and audio tracks into one container file of your choice, with tunable offsets for each track.

  6. A/V sync command line by mungewell · · Score: 5, Informative
    I had a recent project which needed to sync Audio from recorder with video from several cameras. I found this project on GitHub which has a command line tool to measure the delta between the high quality audio from recorder and the low quality from the cameras, and then I could just put this offset in my video editor when inserting the clips.

    https://github.com/allisonnico...