Controlling cinepi‐raw using redis‐cli

When a cinepi-raw instance is started, a connection to the local redis-server is instantiated. This connection serves 2 main purposes:

1. Using redis as store for camera controls and other stateful parameters.

2. To provide bidirectional real-time control, statistics and per frame info to custom user applications via redis pub/sub model.

Key/Channel Index

Listed below are the various channels and keys that perform specific functions within cinepi-raw. These are reserved for cinepi-raw and should be carefully avoided in uses outside of cinepi context.

Channels

• cp_controls
• cp_stats

Keys

• iso
• width
• height
• fps
• is_recording
• shutter_a
• shutter_s
• log_level
• cg_rb
• ucm
• awb
• thumbnail
• thumbnail_size

Testing

For testing users can use the built in redis-cli to test camera controls, for example:

pi@cinepi:~ $ redis-cli
127.0.0.1:6379> subscribe cp_stats
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "cp_stats"
3) (integer) 1
1) "message"
2) "cp_stats"
3) "{\n\t\"bufferSize\" : 0,\n\t\"colorTemp\" : 3333,\n\t\"focus\" : 22.0,\n\t\"frameCount\" : 0,\n\t\"framerate\" : 30.012004852294922\n}\n"
1) "message"
2) "cp_stats"
3) "{\n\t\"bufferSize\" : 0,\n\t\"colorTemp\" : 3333,\n\t\"focus\" : 22.0,\n\t\"frameCount\" : 0,\n\t\"framerate\" : 30.009302139282227\n}\n"
1) "message"
2) "cp_stats"
3) "{\n\t\"bufferSize\" : 0,\n\t\"colorTemp\" : 3333,\n\t\"focus\" : 22.0,\n\t\"frameCount\" : 0,\n\t\"framerate\" : 30.007501602172852\n}\n"
...

This example shows how to subscribe the statistics channel to retrieve per frame metadata and other stats.

Example of live camera controls

Cameras controls follow a 2-step process for updating in real-time application.

1. Setting the key value, as shown below

pi@cinepi:~ $ redis-cli
127.0.0.1:6379> set ***KEY_GOES_HERE***

Examples:

• set iso 100
• set fps 24
• set shutter_a 180
• set is_recording 1

Once the key value is set, the application must now indicate to cinepi-raw to read/update the specific key value within the running camera instance.

2. Publish the key name to the cp_controls channel, as shown below

pi@cinepi:~ $ redis-cli
127.0.0.1:6379> publish cp_controls ***KEY_GOES_HERE***

Examples:

• publish cp_controls iso
• publish cp_controls fps
• publish cp_controls shutter_a
• publish cp_controls is_recording

Used in conjunction this is how you would for example change the iso to 400:

pi@cinepi:~ $ redis-cli 
127.0.0.1:6379> set iso 400
OK
127.0.0.1:6379> publish cp_controls iso
(integer) 1
127.0.0.1:6379> 

In the same way a setting a camera control, you can also read the current value of a camera parameter using a get command:

pi@cinepi:~ $ redis-cli
127.0.0.1:6379> get iso
"400"

⚠ KEY TAKEAWAYS ⚠

1. You MUST set the key/value first
2. You MUST publish the key name to the cp_controls channel. ( without this the application will not update the camera setting during operation. )

Building control apps

Redis has a number of different client integrations through a number of different languages / frameworks, making it very versatile for using in your own control applications. For example, you can use the redis-py python client to achieve the same level of controls as shown in the previous section.