I don't think you'd ever get just playing a sound file to match up with your video. That sounds like a waste of time even trying to me. I'm guessing you want to cut in different shots you're setting up in the film viewer with other video tracks? What I'd done is use one video/audio track as the main track. Only use that audio track for your vid. You can see the waveform of the audio track. I would drag the second video clip around the timeline until something that I can identify in the main video, like guns firing, matches up with the audio track in the main one. You'll see a spike in the waveform when the guns fire. Zoom in on the track to get it synced up. Match up something like a muzzle flash in your secondary clip with the sound of the guns in the primary. Or bomb dropping wth the release sound, and so on. Anyway, that's what I'd do. The sounds are already there for you to use. No need to download anything. Unless I'm misunderstanding what you're trying to do.
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