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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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21 changes: 16 additions & 5 deletions docs/docs/frigate/installation.md
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Expand Up @@ -74,14 +74,25 @@ 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.

```
(width * height * 1.5 * 9 + 270480)/1048576 = <shm size in mb>
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
```

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
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