ffmpeg dumper with "Capture OSD" creates the first segment with 0 frames in it

[tommai78101]

Summary

As shown here in this GIF:

I'm attempting to record on-screen display (OSD) text shown from the RAM Watch window. When about to attempt recording, I noticed that the option to "enable Capture OSD" would enable both the "Capture OSD" and the "Capture Lua" option.

Morilli mentioned this looks wrong. And showed a screenshot of a code snippet suggesting it's wrong:

BizHawk/src/BizHawk.Client.EmuHawk/MainForm.Events.cs

Lines 565 to 571 in 3c3ab65

	private void CaptureOSDMenuItem_Click(object sender, EventArgs e)
	{
	bool c = ((ToolStripMenuItem)sender).Checked;
	Config.AviCaptureOsd = c;
	if (c) // Logic to capture OSD w/o Lua does not currently exist, so disallow that.
	Config.AviCaptureLua = true;
	}

After enabling both options, an attempt to make a small test encoding was made, using the FFmpeg writer, with MP4 default configurations and flags.

It produced 2 movie files, which I named as "test", both of which cannot be played back on a Windows Media Player application. I have attached the 2 movie files here:

test.mp4:
https://user-images.githubusercontent.com/6444116/216873377-d56c7f54-90cf-4d8a-9b39-33bd39cf313a.mp4
test_1.mp4:
https://user-images.githubusercontent.com/6444116/216873378-50e1e34f-c329-457b-92ec-6240a7d79587.mp4

I used the game River City Ransom EX, with a simple RAM Watch properties file (.WCH file, compressed into a ZIP file)
test_ram_watch.zip

SHA-1: 64D0B723AE4EB3F3589B535FB935618F2769229F
CRC32: 8686436E

Thus far, only tested in Bizhawk 2.9 RC2.

Repro

1. In Bizhawk 2.9 RC2, open EmuHawk.
2. Open the game, and load it up using TAStudio.
3. Open the RAM Watch window, and load the .WCH file into the RAM Watch.
4. In the RAM Watch window, enable Settings -> Display Watches on Screen.
5. In EmuHawk, begin recording a movie starting at frame 0.
6. Begin recording with the default configurations for an MP4 file.
7. Record a couple of frames.
8. Stop the recording.
9. EmuHawk should output 2 MP4 files, one of which is named with a _1 suffix.
10. Attempt to open any one of the 2 files will result in not being able to play back the movie files.

Output

No known output exceptions nor error log messages.

Host env.

• BizHawk 2.9 RC2; Win10 x64 Pro 21H2; Intel/NVIDIA (Only tested with the release candidate 2 version.)

[Morilli]

Did a quick test and I can confirm two files get created. The first one seems like an erroneously generated file because it doesn't seem to contain any data, while the second file contains the video as normal.

[tommai78101]

@Morilli Were you able to play the second video normally? I couldn't get the second video to play, and instead, it would crash my Windows Media Player application on me.

[Morilli]

Yeah you probably need a better video player than windows' default for these video files; it should play fine in your browser though.

[tommai78101]

@Morilli Now can confirm the second video can be played back on a newly installed VLC Media Player. It's a shame that the default Windows Media Player can't open the file anymore.

[YoshiRulz]

The code is correct, or at least it correctly implements the desired behaviour according to that comment. (UX needs work, as usual...)

[vadosnaprimer]

Creating a segment with 0 frames can't be correct. It's taking wrong values when initializing an ffmpeg recording, probably assumes OSD is not captured, and then actually sees that resolution is different and splits.

[nattthebear]

It's not desired behavior, but it's also not grossly wrong. If you blindly stitch together all of the segments, it will work fine; if you ignore the empty segment, it will work fine.

[Morilli]

The code is correct, or at least it correctly implements the desired behaviour according to that comment. (UX needs work, as usual...)

How about something like one option saying Capture Lua and the other Capture Lua + OSD, and toggling either switches the other off? Sounds kinda intuitive in my head, and shouldn't be confusing to see.
Of course, these toggles could potentially just be options in the recording dialog itself...