# How to Configure Video Bitrate and Frame Rate Settings for Main and Sub Streams in AtomCam Tools > Learn to configure AtomCam video bitrate and frame rate for main and sub streams using cmd commands or hack.ini for dynamic or persistent settings. - Repository: [Mitsuru Nakada/atomcam_tools](https://github.com/mnakada/atomcam_tools) - Tags: how-to-guide - Published: 2026-03-07 --- **Use the `/scripts/cmd video bitrate` and `/scripts/cmd video fps` commands to adjust stream quality dynamically, or set the `BITRATE_*` and `FRAMERATE` keys in [`hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main/hack.ini) for persistent configuration.** The `atomcam_tools` firmware enhancement for Wyze and Atom cameras exposes low-level video encoder controls that allow precise tuning of network bandwidth and motion smoothness. By manipulating the bitrate and frame rate parameters for the Main (HD) and Sub (360p/320p) streams, you can optimize video quality to match your storage constraints and network upload capacity. ## Understanding Video Stream Channels The camera firmware manages three distinct encoder channels that map to specific stream types: - **Channel 0**: Main stream (HD, AVC/H.264) – typically 300–2000 kbps, default 960 kbps - **Channel 1**: Sub stream (360p/320p, HEVC/H.265) – typically 100–500 kbps, default 180 kbps - **Channel 3**: Main stream alternative (HD, HEVC/H.265) – typically 300–2000 kbps, default 800 kbps According to the source code in [`libcallback/video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/libcallback/video_control.c), the global frame rate (1–30 fps, default ~25 fps) applies to all channels simultaneously rather than individual streams. ## Configuring Video Bitrate ### Runtime Configuration via Command Line For immediate changes that persist until reboot, use the `video bitrate` command followed by the channel number and target bitrate in kbps: ```bash # Set Main AVC stream (channel 0) to 1200 kbps /scripts/cmd video bitrate 0 1200 # Set Sub HEVC stream (channel 1) to 300 kbps /scripts/cmd video bitrate 1 300 # Reset Main HEVC stream (channel 3) to application default /scripts/cmd video bitrate 3 auto ``` The command invokes the `Bitrate()` function in [`/libcallback/video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main//libcallback/video_control.c) (lines 166–176), which validates the input range (10–3000 kbps) before applying the change to the encoder SDK. ### Persistent Configuration via hack.ini To maintain settings across reboots, edit the [`hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main/hack.ini) file located at [`/tmp/hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main//tmp/hack.ini) or on the SD card root: ```ini BITRATE_MAIN_AVC=1500 BITRATE_SUB_HEVC=300 BITRATE_MAIN_HEVC=1800 ``` During boot, [`/overlay_rootfs/scripts/set_icamera_config.sh`](https://github.com/mnakada/atomcam_tools/blob/main//overlay_rootfs/scripts/set_icamera_config.sh) (lines 45–51) reads these values and invokes the same command-line utilities to initialize the encoder. ### Web UI Configuration The web interface at `http://atomcam.local` sends commands through [`/overlay_rootfs/scripts/webcmd.sh`](https://github.com/mnakada/atomcam_tools/blob/main//overlay_rootfs/scripts/webcmd.sh) (lines 51–58). Selecting bitrate options triggers the underlying `/scripts/cmd video bitrate` utility with the appropriate channel parameters. ## Configuring Frame Rate The frame rate setting affects all video channels globally and must be within the 1–30 fps range. ### Command Line Adjustment Execute the `video fps` command to change the encoder frame rate immediately: ```bash # Set global frame rate to 25 fps /scripts/cmd video fps 25 ``` This calls the `Framerate()` function in [`libcallback/video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/libcallback/video_control.c) (lines 167–176), which validates that the value falls between 1 and 30 fps before reconfiguring the encoder timing. ### Persistent Frame Rate Settings Add the following to your [`hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main/hack.ini) configuration: ```ini FRAMERATE=25 ``` The boot script [`set_icamera_config.sh`](https://github.com/mnakada/atomcam_tools/blob/main/set_icamera_config.sh) applies this value during system initialization, ensuring consistent motion characteristics across all streams. ## Technical Implementation Details The configuration system relies on three critical components in the `mnakada/atomcam_tools` repository: - **[`/libcallback/video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main//libcallback/video_control.c)**: Contains the `Bitrate()` and `Framerate()` parsing functions that validate input ranges and interface with `local_sdk_video_stop/start` to restart encoder channels when parameters change. - **[`/overlay_rootfs/scripts/set_icamera_config.sh`](https://github.com/mnakada/atomcam_tools/blob/main//overlay_rootfs/scripts/set_icamera_config.sh)**: Parses [`hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main/hack.ini) at boot time and translates configuration keys into executable commands. - **[`/overlay_rootfs/scripts/webcmd.sh`](https://github.com/mnakada/atomcam_tools/blob/main//overlay_rootfs/scripts/webcmd.sh)**: Acts as a bridge between the HTTP web interface and the command-line utilities. When you modify bitrate or frame rate, the firmware executes a stop-start sequence on the affected encoder channels (0, 1, and 3), causing a brief video interruption while the new parameters take effect. ## Important Considerations **Validation Limits**: The `Bitrate()` function rejects values below 10 kbps or above 3000 kbps, while `Framerate()` enforces a 1–30 fps boundary. Invalid inputs return an "error" response without modifying the encoder. **Auto Reset**: Specifying `auto` for any bitrate channel clears the user override (`userBitrate[ch]=0`) and restores the application default (`appBitrate[ch]`) defined by the firmware. **Encoder Restart**: Every bitrate or frame rate change triggers a restart of the video encoder channels. Expect a momentary stream interruption when applying new settings. ## Summary - Use `/scripts/cmd video bitrate ` for immediate bitrate changes on channels 0 (Main AVC), 1 (Sub HEVC), or 3 (Main HEVC). - Use `/scripts/cmd video fps ` to set the global frame rate between 1–30 fps. - Configure `BITRATE_MAIN_AVC`, `BITRATE_SUB_HEVC`, `BITRATE_MAIN_HEVC`, and `FRAMERATE` in [`hack.ini`](https://github.com/mnakada/atomcam_tools/blob/main/hack.ini) for persistent boot-time settings. - All changes restart the encoder channels briefly; valid ranges are enforced by [`video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/video_control.c). - The web UI, command line, and configuration file all interface with the same underlying SDK functions. ## Frequently Asked Questions ### What are the valid bitrate ranges for each stream? According to the `atomcam_tools` README and source validation in [`video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/video_control.c), Main streams (channels 0 and 3) support 300–2000 kbps, while the Sub stream (channel 1) typically operates between 100–500 kbps. The absolute technical limits enforced by the firmware are 10–3000 kbps. ### Why does my video stream briefly cut out when changing settings? The `local_sdk_video_stop/start` sequence in [`video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/video_control.c) (lines 60–70) restarts the encoder channels to apply new timing and compression parameters. This architectural requirement ensures clean initialization of the hardware encoder but causes a momentary interruption. ### Can I set different frame rates for Main and Sub streams? No. The frame rate is a global encoder setting that applies to all channels simultaneously. The `Framerate()` function in [`video_control.c`](https://github.com/mnakada/atomcam_tools/blob/main/video_control.c) configures the base timing for the entire video subsystem rather than individual streams. ### What happens if I specify a bitrate outside the allowed range? The `Bitrate()` function returns an "error" string and ignores the command if the value is less than 10 kbps or greater than 3000 kbps. Similarly, `Framerate()` rejects values outside the 1–30 fps range. You must specify values within these boundaries for the settings to take effect.