Recording - All output files corrupted

First and foremost consider this:

Description

No exception, it seems the first key frames of the output files are empty or corrupted.

Expected behavior

The video files should be solid from back to back.

Actual behavior

While we can play the video, depending on the player, without problems, editing it or resuming from a previous state results in garbled reproduction, indistinguishable codec ouput.

Steps to reproduce the bug

1. Start and stop recording for a few seconds, or minutes if needed
2. Play the video, it mostly will be OK, if you put the player to resume from where it stopped, you'll see the file is actually corrupted
3. I cut the last 10 seconds and later the first 10 seconds of the ouput file without recoding it, I noticed the file was totally corrupted when cutting the first secs, interestingly, checking properties\details in Windows I see it shows, among other info, "0 FPS", possibly indicating empty or corrupted first video frames.

Bisect Results

[Try to bisect and tell us when this started happening]

Version/Commit

Build Date: Feb 3 2020
Git Version: fdb7f972a6

• RetroArch: 1.8.4, nightly

Environment information

• OS: Windows 10 x64
• Compiler: [In case you are running local builds]

Start by reproducing the recording workflow on Windows 10 with RetroArch 1.8.4 at commit fdb7f972a6, then check the output when played, resumed, or cut without re-encoding. Done means recordings have valid initial frames and remain intact when resumed or edited from the beginning.