Replay Buffer Maximum Memory Supported

[NMiranda]

Hi,
I've been searching for documentation of the Replay Buffer feature in OBS (currently using the latest version 29.1.2) because I need to save 60 minute clips for further edits which is ideal to avoid SSD degradation by recording many hours of useless footage in it and would help a lot in the edition process. Currently my recording settings are 1440p 60fps at High Quality. From the documentation and topics that I found on the Replay Buffer feature from 2018-2021, it's mentioned that the max RAM size is capped at 8GB. But when testing the feature it allows me to set higher values which I set to 32000 MB to have enough space for high quality recordings (I have 128GB of RAM in my PC).

Is the Replay Buffer feature still capped to 8GB of RAM or is it actually working with the values I set in the configurations?

Thanks so much in advance for the help.

 

[koala]

avoid SSD degradation

You can ignore any thoughts about this. You will not wear out any current SSD.

For example, if you have a Samsung EVO 970 2 TB with 1200 TB TBW (is designed to write 1200 TB in its lifetime), and you're recording with an average of 40 MB/s (I don't remember what the "high quality" quality setting will produce at average, but it's probably less than that), this is the computation:
1200 TB are 1200.000 GB are 1200.000.000 MB.
1200.000.000 MB / 40 MB/s = 30.000.000 s.
You need to record 30 Mio seconds with 40 MB/s to wear out that SSD.
30 Mio seconds are 30.000.000 / 86400 s/day = 347 days
That means you need to continuously write 40 MB per second for more than a year to wear down that SSD. Nonstop, 24h a day, every day.
If you write 4 hours per day the whole lifetime of that SSD instead of 24h, you get a lifetime of 347 / 4 * 24 = 2083 = 5.7 years. That means if you record videos every single day of that about 6 years, 4 hours a day.
This is very unlikely. More likely is you write 4 hours a day for not more than perhaps 3-4 days a week. This is half of the time, i. e. the lifetime of the SSD doubles to about 10-11 years (which has a manufacturer guarantee of only 5 years).
Usually, SSDs last way longer actually than the manufacturer TBW, 50-100% longer, so it's even 2-5 years more.
If you're a professional, you have the money to buy replacement SSDs.
If you're not a professional, you will actually record much less than that, i. e. the lifetime of such a SSD is even times longer. If you just occasionally record videos, once a week or so, this recording isn't really counting to the lifetime. It's more likely you will replace it with something faster.

tl;dr
Don't think about SSD degradation. It will not happen. Just use the SSD for whatever you need it. Video processing is the ideal use case for SSD usage because of the high throughput and high iops. If not for video processing, for what do you have that SSD? You can get away with a spinning disk for everything else, but video processing is THE thing for an SSD.

 

[NMiranda]

You can ignore any thoughts about this. You will not wear out any current SSD.

For example, if you have a Samsung EVO 970 2 TB with 1200 TB TBW (is designed to write 1200 TB in its lifetime), and you're recording with an average of 40 MB/s (I don't remember what the "high quality" quality setting will produce at average, but it's probably less than that), this is the computation:
1200 TB are 1200.000 GB are 1200.000.000 MB.
1200.000.000 MB / 40 MB/s = 30.000.000 s.
You need to record 30 Mio seconds with 40 MB/s to wear out that SSD.
30 Mio seconds are 30.000.000 / 86400 s/day = 347 days
That means you need to continuously write 40 MB per second for more than a year to wear down that SSD. Nonstop, 24h a day, every day.
If you write 4 hours per day the whole lifetime of that SSD instead of 24h, you get a lifetime of 347 / 4 * 24 = 2083 = 5.7 years. That means if you record videos every single day of that about 6 years, 4 hours a day.
This is very unlikely. More likely is you write 4 hours a day for not more than perhaps 3-4 days a week. This is half of the time, i. e. the lifetime of the SSD doubles to about 10-11 years (which has a manufacturer guarantee of only 5 years).
Usually, SSDs last way longer actually than the manufacturer TBW, 50-100% longer, so it's even 2-5 years more.
If you're a professional, you have the money to buy replacement SSDs.
If you're not a professional, you will actually record much less than that, i. e. the lifetime of such a SSD is even times longer. If you just occasionally record videos, once a week or so, this recording isn't really counting to the lifetime. It's more likely you will replace it with something faster.

tl;dr
Don't think about SSD degradation. It will not happen. Just use the SSD for whatever you need it. Video processing is the ideal use case for SSD usage because of the high throughput and high iops. If not for video processing, for what do you have that SSD? You can get away with a spinning disk for everything else, but video processing is THE thing for an SSD.

Thanks so much for the reply. I'm aware of how SSD endurance works but I have a 500GB SSD nvme that I use for my OS which already have some wear on it. But given that I have enough RAM to use for that I would prefer to use the Replay Buffer option until I'm able to upgarde the SSD. I record classes 4-5 per day of 1.5+ hours each and Replay Buffer would really help in the highlight edition if it works for 1 hour.

Anyways that doesn't answer the question about the Replay Buffer.

 

[koala]

The maximum replay buffer size is 75% of installed physical RAM. It's enforced in the GUI, so you cannot enter more than this value.

But do you really have 128 GB of RAM and only 500 GB SSD? That's a big disparity. You have the money for 128 GB RAM, about 380 Euro, and no money for some 2 TB NVMe SSD for about 100 Euro? I just bought a new PC with 2x2TB NVMe SSD to get rid of all spinning disks, which are slow, loud, more error prone, and use more electrical power. That simply has to be in the budget of such a PC, especially if built for video processing.

 

[NMiranda]

The maximum replay buffer size is 75% of installed physical RAM. It's enforced in the GUI, so you cannot enter more than this value.

Thanks so much for the information.

But do you really have 128 GB of RAM and only 500 GB SSD? That's a big disparity. You have the money for 128 GB RAM, about 380 Euro, and no money for some 2 TB NVMe SSD for about 100 Euro?

It's sounds silly but yes. I built my PC with expensive parts (CPU/GPU/PSU/Mobo/RAM/etc) and I had to save money on something to be able to get them. As I already had an old SSD I decided to use it until I can get a new set of SSDs which will be in a month or so.

 

[Suslik V]

Replay uses circular buffer:

obs-studio/libobs/util/circlebuf.h at master · obsproject/obs-studio

OBS Studio - Free and open source software for live streaming and screen recording - obsproject/obs-studio

github.com

size may vary from machine to machine. But in most cases encoded media file wouldn't allow you to go beyond 9,223,372,036,854,775,807 bytes when it saved on disk.

OBS set limitations (3/4 of total RAM or 8192 MiB if total amount of RAM for the machine is unknown) in:

https://github.com/obsproject/obs-studio/blob/a35e5aae4116f6570a72a3e30f57142e59566063/UI/window-basic-settings.cpp#L5676

You can try to test your setting by using CBR rate control for software x264 encoder (it uses padding) for Output Mode: Advanced and setting bitrate at 400000 Kbps (~49 MiByte/s) ---> your 32 GiB will be filled in ~11 minutes.

But replay buffer wouldn't warn you that your disk is full and silently(!) overwrite your recording. Better look at the RAM disks emulators (https://en.wikipedia.org/wiki/List_of_RAM_drive_software).