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  1. Member
    Join Date: Aug 2014
    Location: United Kingdom
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    I have an electric drum set and have just recorded 3 videos of covers (this problem occurs on all 3). I record the audio using audacity and I record the video using my Olympus D-745 (not the best for video but it's all I have) I then compile the two tracks and edit in camtasia. I also do one hit of the symbols at the start to sync the audio and video. When I synced up the audio and video (using the cymbal hit) it is perfect for about 20 seconds, then the audio slowly starts to come out of sync with the video so that by the end it is almost 5 seconds out. What is the cause of this and does anyone know how to fix it??

    Edit: It is goes out of sync both in camtasia and in the video file after rendering.

    http://youtu.be/HCWKWFFFVys
    Last edited by kjthoward; 15th Aug 2014 at 16:44. Reason: video uploaded
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  2. Member turk690's Avatar
    Join Date: Jul 2003
    Location: ON, Canada
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    First, please post computer details (hardware where audacity is installed (mainboard chipset, processor, memory, graphics, sound card details, including how the drum set is connected to it)). Then use mediainfo (tree view) to get details of the file produced by the olympus and and post those details here.
    This problem is common, when disparate and separate devices are used to record audio and video. In professional circles, all audio and video recorders receive a common sync, so timecode across all devices involved in recording a scene are the same and absolute. For prosumers like us, getting rid of it falls in mainly two camps. The first involves examining the audio and video end to end to see the total time difference of the two, down to the last frame (or millisecond). Then audio is stretched or compressed to the exact length of the video. Audacity can do this. Changing the audio this way can produce artifacts, though, and may be time-consuming the longer the involved clips are (2hrs or more). So, the second involves finding natural pauses and breaks in audio, splitting it at those points, then moving the cut clips to sync with the corresponding video at that point. Stretching (or compressing, temporally that is) wasn't done so it can be simpler. Generally, we only become sensitive to loss of sync between audio and video when it becomes more than 4 or 5 frames worth, so the second method just redistributes the loss of sync in amounts too little to be noticed more or less evenly across the program.
    Current prosumer equipment (camcorders and audio recorders) can generally be considered accurate enough such that when a random two (a camcorder and an audio recorder) are chosen, they can be expected to record a clip of about (in my experience) 10 minutes before they begin to slip by a frame or two (still too little to be noticed). This is my personal rough benchmark of how accurate the timekeeping abilities are when handling unknown equipment. By around the 30-minute mark (of a continuous, uninterrupted take) that's when loss of sync becomes obvious. This is why your computer details are important, because there seems to be something grossly wrong, electronically, when audio and video start to come out of sync a mere 20 seconds into it. How long are each of the three videos?
    It may or may not also have anything to do with camtasia; I would instead use something like Premiere elements to edit the clips with.
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  3. Member
    Join Date: Aug 2014
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    Computer details:
    MOTHERBOARD: Mobile Intel HM87 Express Chipset Mainboard
    CPU: Intel® Core™ i7-4800MQ Mobile Processor 2.70 GHz
    MEMORY: 16GB (8GBx2) DDR3-1600 SODIMM Memory
    VIDEO: NVIDIA GTX 765M 2GB PCIe Video
    SOUND: HD Audio w/ Sound Blaster Cinema Technology
    CONNECTION: 3.5mm audio jack from "audio out" on drums (Alesis DM-6), into the microphone port)

    Mediainfo:
    http://prntscr.com/4d7kku
    http://prntscr.com/4d7kyd
    http://prntscr.com/4d7l1k

    The raw video clip is about 5:20 and the audio track is about 5:15. Also I have used camtasia for lots of stuff before and have never had this issue.
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  4. Member turk690's Avatar
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    Originally Posted by kjthoward View Post
    Computer details:
    MOTHERBOARD: Mobile Intel HM87 Express Chipset Mainboard
    CPU: Intel® Core™ i7-4800MQ Mobile Processor 2.70 GHz
    MEMORY: 16GB (8GBx2) DDR3-1600 SODIMM Memory
    VIDEO: NVIDIA GTX 765M 2GB PCIe Video
    SOUND: HD Audio w/ Sound Blaster Cinema Technology
    CONNECTION: 3.5mm audio jack from "audio out" on drums (Alesis DM-6), into the microphone port)
    The computer specs are IMHO good enough for what you want to do, but "mobile" is written all over it. Is it a laughtop? If so, connect an external hard drive to to it (preferably eSATA) and direct the audio that audacity makes to it. Avoid putting media files, rendered files, projects, etc on the system drive. Avoid compressed formats; capture to *.wav and put these audio files along with the olympus *.avi files on the external hard drive. Laughtops (and most branded desktops) are notorious for being laden with malware, trashware, crapware, some obvious, others not, that get installed when computer is powered on for the first time. These include, but are not limited to little prickly programs that TSR like printer monitors, messaging, even anti-virus, that can all wreak havoc with doing anything that involves HD video. Turn off wi-fi, LAN, blutut, while engaging in your activity as well.
    The olympus produces *.avi with a quixotic MJPEG codec, with an integer frame rate at that, that may take the lion's share of decoding by your CPU. You may or may not have the latest codecs for the OS you are using (what OS is it?) such that it drops or repeats frames, enough for sync to get messed up between audio and video. In your screenshots the audio isn't included; what is it? Does the camera also record audio?
    If everything is OK (meaning the camcorder and audio recorder have accurate timebases and recorded non-corrupt clips that use supported codecs when brought into the editing computer), two separate devices shouldn't drift in sync to a noticeable point in clips recorded around 5mins. So, after the clips are on the computer, without editing them or doing anything to them, load them individually in, say, vlc, then manually time them to see just how long they are. If they seem to be roughly the same length then putting them on the camtasia timeline is doing something nasty to them. Camtasia is geared primarily to screen capture. It may be good for the previous projects that you did, but for doing something as involving and as delicate as syncing audio with MJPEG *.avi I'd use something else.
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  5. Member
    Join Date: Aug 2014
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    it is indeed a laptop. I am not technically recording to the system drive (My OS (windows 8)) in installed on the SSD and all data is written to an internal HDD. It does have the most up to date drivers, I don't have any trashware on it or anything. and I always have bluetooth off, and I had wireless off at time of the recording. The camera can record audio but it has no audio in, so it'd just pick up the hitting of the pads, not the sounds.

    I have managed to fix the issue though, by doing as you said and stretching/compressing the audio to the exact length of the video. Although it was tricky as I stop the audio and video at different times. In future if I do another 'syncing' hit at the end that should give me an addition reference point to change the run speed of the audio to match the video.

    thank you for all your help.
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