Final Audio/Video is out of sync

We've had this issue a few times where the finished audio/video stays in sync for the first bit but eventually it will slowly fall out of sync with each other. The first few weeks we weren't having this issue. Have I missed something or do i need to do something extra to make it work?

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  • Sorry you're experiencing this issue but I need clarification in order to help.
    First please update to Wirecast 7.4 and test.

    It's not clear to me what the file is and how it was used or generated or how sync was tested.

    Wirecast can play files. It can also create files through local recording or server based recording.

    If there was no issue at first but later developed than something has changed but I'd need information in order to determine that. Perhaps something about your workflow, sources, recording methods changed.

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  • Not sure if this helps, but I've noticed our saved MP4's get save in a variable framerate that play fine in things like Quicktime player, but if dragged into an editing program look out of sync. We always use handbrake to conform the MP4 into a constant frame rate file before any editing. Just a shot in the dark.

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  • Daniel Risk That's expected behavior. Wirecast records a variable frame rate to avoid dropped frames. Dropped frames would result in stuttering whereas as variable frame rate retains smooth motion.

    File players generally don't care about frame rate so they would remain in sync.
    NLEs are designed to lock to standard video frame rates. Locking the variable frame rate file changes the speed of the video relative to the audio, resulting in sync drifting out over time.

    One solution is to re-encode the file exactly as you are doing as that locks the file to a standard constant frame rate. An excellent suggestion.

    My personal preferences with Wirecast is to record in Apple ProRes on Mac or MJPEG on Windows since the quality of those files generally hold up better when re-encoded.

    An alternate solution is to use the "time stretch" feature (may have different name in different NLEs) on the video to stay in sync with the audio.

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  • Regarding that it didn't happen the first few times but now it does, there are several factors. With enough throughput Wirecast can certainly record at the targeted frame rate. Hard drive speed and connection throughput to the drive can vary depending on other activity on the computer, the bus, the fullness of the drive. The best results would be on RAID0 striped drives or SSD drives on a very fast bus (PCIe, Thunderbolt, etc).

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