Recording does not check whether the target path exists already

[zenorbi]

Operating System Info

Windows 11

Other OS

No response

OBS Studio Version

Other

OBS Studio Version (Other)

29.1.3

OBS Studio Log URL

The 2 logs are provided in the description

OBS Studio Crash Log URL

No response

Expected Behavior

Have 1 file per recording (so 2 files, one of them with some suffix number)

Current Behavior

Only 1 file is produced in total that has inter-mangled data.

Steps to Reproduce

1. Start 2 OBS instances
2. Have 2 different video content for the 2 OBS instances
3. Click the Start Recording button in the same second so that the resulting file would have the same exact name

Anything else we should know?

OBS 1:

15:41:54.213: ==== Recording Start ===============================================
15:41:54.213: [ffmpeg muxer: 'adv_file_output'] Writing file 'C:/Users/Specto/Videos/2024-05-29 15-41-54.mkv'...
16:42:08.155: [ffmpeg muxer: 'adv_file_output'] Output of file 'C:/Users/Specto/Videos/2024-05-29 15-41-54.mkv' stopped
16:42:08.155: Output 'adv_file_output': stopping
16:42:08.155: Output 'adv_file_output': Total frames output: 216774
16:42:08.155: Output 'adv_file_output': Total drawn frames: 216835 (216836 attempted)
16:42:08.155: Output 'adv_file_output': Number of lagged frames due to rendering lag/stalls: 1 (0.0%)
16:42:08.156: Video stopped, number of skipped frames due to encoding lag: 1/216834 (0.0%)
16:42:08.157: ==== Recording Stop 

OBS 2:

15:41:54.853: ==== Recording Start ===============================================
15:41:54.853: [ffmpeg muxer: 'adv_file_output'] Writing file 'C:/Users/Specto/Videos/2024-05-29 15-41-54.mkv'...
15:42:23.743: User switched to scene 'Zoom Only'
15:42:32.772: User switched to scene 'Presentation Only'
16:05:43.747: User switched to scene 'Zoom Only'
16:10:03.685: User switched to scene 'Picture in Picture'
16:14:39.364: User switched to scene 'Presentation Only'
16:42:08.954: [ffmpeg muxer: 'adv_file_output'] Output of file 'C:/Users/Specto/Videos/2024-05-29 15-41-54.mkv' stopped
16:42:08.954: Output 'adv_file_output': stopping
16:42:08.954: Output 'adv_file_output': Total frames output: 216785
16:42:08.954: Output 'adv_file_output': Total drawn frames: 216846
16:42:08.954: ==== Recording Stop 

2024-05-29 15-07-36.txt
2024-05-29 15-07-42.txt

[RytoEX]

We do not accept bug reports for older versions of OBS Studio. Please test and provide logs for OBS Studio 30.1.2 or newer.

[zenorbi]

I have retested with OBS 30.1.2, the issue remains, here are the new logs:

https://obsproject.com/logs/fNBPyO0ASU5Qtka6
https://obsproject.com/logs/oJo8YbOBVlXql726

[derrod]

OBS does check if a file already exists unless the "Overwrite if file eixsts" option is enabled in advanced settings. It's possible that you're running into a race condition where the file simply does not exist yet by the time the check runs. Just use different output folders or filename formats.

[zenorbi]

I do not have the "Overwrite if file exists" option checked and I am clicking the 2 buttons manually with around 300ms in between (according to the logs).

Just for testing I have changed the format to always collide and I can confirm that given enough time between the 2 button presses, OBS will create a second file with (2) in the filename, so this looks to be a race condition.

Next time I will write to different folders but this was just bad luck where I have lost one of my recordings due to this, but I believe in reporting issues even if I already know the solution (for example, wait 1 second between starting each recording session).

[derrod]

There are some things we could try to prevent this at least, e.g. the first instance to decide on a filename could touch the file so it exists as a 0-byte placeholder until the output and encoder are ready to start writing actual data.

We can probably leave this open for now.