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Fix shm size calculation #5123

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merged 4 commits into from
Jan 18, 2023
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Fix shm size calculation #5123

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655f8e3
Fix shm size calculation
felipecrs Jan 17, 2023
95974ee
Improve shm examples
felipecrs Jan 17, 2023
6e9362b
Add note about default shm size for add-ons
felipecrs Jan 17, 2023
49b74dc
adjust language
blakeblackshear Jan 18, 2023
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24 changes: 18 additions & 6 deletions docs/docs/frigate/installation.md
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Expand Up @@ -74,17 +74,29 @@ database:

### Calculating required shm-size

Frigate utilizes shared memory to store frames during processing. The default `shm-size` provided by Docker is 64m.
Frigate utilizes shared memory to store frames during processing. The default `shm-size` provided by Docker is **64MB**.

The default shm-size of 64m is fine for setups with 2 or less 1080p cameras. If Frigate is exiting with "Bus error" messages, it is likely because you have too many high resolution cameras and you need to specify a higher shm size.
The default shm size of **64MB** is fine for setups with **2 cameras** detecting at **720p**. If Frigate is exiting with "Bus error" messages, it is likely because you have too many high resolution cameras and you need to specify a higher shm size.

You can calculate the necessary shm-size for each camera with the following formula using the resolution specified for detect:
The Frigate container also stores logs in shm, which can take up to **30MB**, so make sure to take this into account in your math as well.

You can calculate the necessary shm size for each camera with the following formula using the resolution specified for detect:

```console
# Replace <width> and <height>
$ python -c 'print("{:.2f}MB".format((<width> * <height> * 1.5 * 9 + 270480) / 1048576))'

# Example for 1280x720
$ python -c 'print("{:.2f}MB".format((1280 * 720 * 1.5 * 9 + 270480) / 1048576))'
12.12MB

# Example for eight cameras detecting at 1280x720, including logs
$ python -c 'print("{:.2f}MB".format(((1280 * 720 * 1.5 * 9 + 270480) / 1048576) * 8 + 30))'
126.99MB
```
(width * height * 1.5 * 9 + 270480)/1048576 = <shm size in mb>
```

The shm size cannot be set per container for Home Assistant Addons. You must set `default-shm-size` in `/etc/docker/daemon.json` to increase the default shm size. This will increase the shm size for all of your docker containers. This may or may not cause issues with your setup. https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file
The shm size cannot be set per container for Home Assistant add-ons. However, this is probably not required since by default Home Assistant Supervisor shares the host `/dev/shm` with all add-ons. Usuallly the host `/dev/shm` has half the size of your total memory, so if your machine has 8GB of memory, chances are that Frigate will have access to up to 4GB there without any additional configuration.


### Raspberry Pi 3/4

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