Blender Video & Audio out of horribly sync and missing my cuts

Question

My audio acts as though it was never cut. I found a place in the output file where it most certainly ran over my cut like there was nothing to indicate that it should have cut off. it's annoying since despite the erroneous output my audio's cut point is still in sync with the time code (roughly half way), it just keeps running as though I did nothing.

I have no idea what is going on with the video; It is out of sync and missing my cuts. It seems like the video is mostly the part before the halfway mark and then towards the end it decides to play catch-up and shows the last bit.

It is a little galling as I have done editing on previous videos and had no problems, but this video seems eager to stand out in a bad way.

It is unfortunately a very long video (03h, 42m, 34s - took 22 hours to render both times so far) so getting multiple tests out of the way is out of the question and makes this all the more frustrating.

On the off chance that it helps, here is the encoding info; which I have used for successful rendering of 3 previous videos of similar length. It may also be helpful to note that I used the same .blend file for all of these videos as well; deleting the old and loading new files to be edited.

Blender v2.79

• Output - FFmpeg
• Container - MPEG-4
  • Video codec - H.264 (30fps)
    • Output quality - Low
    • Encoding Speed - Fast
  • Audio codec - AAC (Bitrate - 192)

I'm going to test with smaller snippets of the video to see if there are any problems on a more micro level.

Answer 1

There were small errors, 4 in total, in the video. Places where the video and audio would freeze for ~10-15 seconds which threw off Blender's A/V syncing.

While editing the errors out in Blender I discovered that allowing it to slowly advance while rewinding and listening helped in isolating the bad spots. The audio/video would always resume playing from the same place, despite the advancing rewind point, until I reached the end of the corruption then play would advance normally.

I hope my explanation was clear. Be sure to check your videos for corrupt sections before editing. Good luck!