doc:appunti:hardware:sjcam-8pro-custom-firmware
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doc:appunti:hardware:sjcam-8pro-custom-firmware [2022/06/27 19:00] – [My Custom firmware] niccolo | doc:appunti:hardware:sjcam-8pro-custom-firmware [2023/06/09 07:38] (current) – [My Custom firmware] niccolo | ||
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The **SCAM SJ8 Pro** is a mid-range priced action camera, equipped with chips well known for their quality: the **Ambarella H22 S85** and the **Sony IMX377** sensor. Still in 2022 it was well placed between the expensives GoPros and the plethora low-end budget cameras. Unfortunately the support from SJCAM was ended in 2020 with the **firwmare 1.3.2** still affected by various bugs, image quality and video codec settings **definitely to be improved**. Also the Adnroid app is disappointing. | The **SCAM SJ8 Pro** is a mid-range priced action camera, equipped with chips well known for their quality: the **Ambarella H22 S85** and the **Sony IMX377** sensor. Still in 2022 it was well placed between the expensives GoPros and the plethora low-end budget cameras. Unfortunately the support from SJCAM was ended in 2020 with the **firwmare 1.3.2** still affected by various bugs, image quality and video codec settings **definitely to be improved**. Also the Adnroid app is disappointing. | ||
- | Fortunately enough, being equipped with the Ambarella chip, it was possible to **reverse engineer** some of its firmware and API. Creating a custom firmware you can imporove | + | Fortunately enough, being equipped with the Ambarella chip, it was possible to **reverse engineer** some of its firmware and API. Creating a custom firmware you can improve |
The main honorable mention goes to the hacker **VMax**, which created the software **[[https:// | The main honorable mention goes to the hacker **VMax**, which created the software **[[https:// | ||
- | See my other page about the SJCAM SJ8 Pro action camera: **[[sjcam-8pro]]**, **[[sjcam-8pro-ambarella-firmware-modding]]** | + | **WARNING**: |
+ | |||
+ | See my other page about the SJCAM SJ8 Pro action camera: | ||
+ | |||
+ | * **[[sjcam-8pro]]** | ||
+ | * **[[sjcam-8pro-ambarella-firmware-modding]]** | ||
+ | * **[[sjcam-8pro-ambarella-wifi-api]]** | ||
===== My Custom firmware ===== | ===== My Custom firmware ===== | ||
- | Download the custom firmware here: **{{.: | + | Download the custom firmware here: |
+ | |||
+ | * **{{.: | ||
This is a breif list of customizations, | This is a breif list of customizations, | ||
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* Increased **bitrates**, | * Increased **bitrates**, | ||
* Increased **keyframes** rates (reducing GOP-N): one keyframe every 1/4 second instead of 1 per second. | * Increased **keyframes** rates (reducing GOP-N): one keyframe every 1/4 second instead of 1 per second. | ||
- | * **YUV color profiles**: all the three profiles **Default**, | + | * **YUV color profiles**: all the three profiles **Default**, |
- | * Fixed **exposition** profiles: **Center**, **Spot** and **Average**. | + | * Fixed **exposition** profiles: **Center**, **Spot** and **Average** |
* Changed **gamma curves**: added some brightness to shadows with an overall gamma coefficient of 1.10 and removed a slight red casting when using Auto White Balance in early hours of sunny days. All the gamma tables for video modes are the same, for photo modes we leaved a linear gamma (1.0) for R, G and B. | * Changed **gamma curves**: added some brightness to shadows with an overall gamma coefficient of 1.10 and removed a slight red casting when using Auto White Balance in early hours of sunny days. All the gamma tables for video modes are the same, for photo modes we leaved a linear gamma (1.0) for R, G and B. | ||
* Change **chroma curves** to reduce banding in blue sky and to attenuate over-saturated colors. | * Change **chroma curves** to reduce banding in blue sky and to attenuate over-saturated colors. | ||
- | * Changed power-on, power-off and photo shutter **sounds** with louder ones. | + | * Changed power-on, power-off and photo shutter **sounds** with **louder** ones. |
* Disabled **LRV** (low resolution videos) recording. | * Disabled **LRV** (low resolution videos) recording. | ||
- | === Bitrates === | + | ==== Bitrates |
The SJ8 Pro camera has by default very low bitrates compared with other 4K action cameras. In the following table you can compare three cameras in various video modes. My custom settings are geared to always keep the standard quality and to film mainly at 1920x1080, to save space and battery. | The SJ8 Pro camera has by default very low bitrates compared with other 4K action cameras. In the following table you can compare three cameras in various video modes. My custom settings are geared to always keep the standard quality and to film mainly at 1920x1080, to save space and battery. | ||
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**NOTICE**: For bitrates of **100 Mbit/s** or above you have to consider the micro SD card performances. Recording a stream of 100 Mbit/s means writing a **sustained stream of 12 Mb/s** (megabytes/ | **NOTICE**: For bitrates of **100 Mbit/s** or above you have to consider the micro SD card performances. Recording a stream of 100 Mbit/s means writing a **sustained stream of 12 Mb/s** (megabytes/ | ||
- | === Bitrates GOP === | + | ==== Bitrates GOP ==== |
I want at least 4 keyframes per second, so I can cut scenes without re-encoding with the precision of about 0.25 seconds. The original firmware instead put only a keyframe every second. | I want at least 4 keyframes per second, so I can cut scenes without re-encoding with the precision of about 0.25 seconds. The original firmware instead put only a keyframe every second. | ||
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^ My Custom SJ8Pro | ^ My Custom SJ8Pro | ||
- | === YUV Profiles === | + | **WARNING**: |
+ | ==== YUV Profiles | ||
- | For my taste the two YUV profiles are both too exagerated. The **Vivid - SJCAM** profile has **too much contrast** and colors are **too much saturated**, | + | For my taste the two YUV profiles |
- | For the **default** and **vivid** profile | + | In my custom firmware |
- | + | ||
- | The resulting two profiles are not so different from each other, may be you cannot tell them apart looking at the touch screen. This may be a problem, because of the firmware bug which does not properly show the selected | + | |
^ | ^ | ||
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^ V-offset | ^ V-offset | ||
- | === Exposition === | + | ==== Exposition |
Metering tables were fixed, this simply means swapping profiles **Spot** and **Average**. | Metering tables were fixed, this simply means swapping profiles **Spot** and **Average**. | ||
- | === Gamma curves === | + | ==== Gamma curves |
There is no documentation on how the **%%*/ | There is no documentation on how the **%%*/ | ||
* Group **%%*/0%%** is not used at all. | * Group **%%*/0%%** is not used at all. | ||
- | * Groups | + | * When using **dynamic ISO modes**, groups |
+ | * When using **fixed ISO modes** it seems instead that groups **%%*/ | ||
* It seems that in some **particular circumstances** (some color component of */255 is **very dark**) the gamma curve is replaced automatically with something different, may be a **negative** (descending) curve. | * It seems that in some **particular circumstances** (some color component of */255 is **very dark**) the gamma curve is replaced automatically with something different, may be a **negative** (descending) curve. | ||
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* The camera produces rather **fair colors** when set with **neutral gamma** tables and **neutral YUV** profiles. | * The camera produces rather **fair colors** when set with **neutral gamma** tables and **neutral YUV** profiles. | ||
* The stock firmware have somewhat **exagerated saturation and contrast**, just simply reducing them produces a better video quality (in my humble opinion). | * The stock firmware have somewhat **exagerated saturation and contrast**, just simply reducing them produces a better video quality (in my humble opinion). | ||
- | * The **non-automatic white balance** settings (e.g. sunny, cloudy, etc.) produce some un-natural color casting. It is possibile to correct it using **gamma** or **YUV**, but if you fix e.g. the sunny white balance, you will break the others, including the //auto// mode. | + | * The **non-automatic white balance** settings (e.g. sunny, cloudy, etc.) produce some un-natural color casting. It is possibile to correct it using **gamma** or **YUV**, but if you fix e.g. the sunny white balance, you will break the others, including the auto mode. |
Finally I decided to favor the automatic white balance setting: first of all I set a gamma value of **1.10** on all the RGB channels to reduce shadows, then I added some gray balance using the gamma values **(0.973, 1.013, 0.960)** for the three RGB channels. This correction penalizes the images taken in the central hours of the day, but in my opinion it is better for the ones taken in the morning and in the afternoon. | Finally I decided to favor the automatic white balance setting: first of all I set a gamma value of **1.10** on all the RGB channels to reduce shadows, then I added some gray balance using the gamma values **(0.973, 1.013, 0.960)** for the three RGB channels. This correction penalizes the images taken in the central hours of the day, but in my opinion it is better for the ones taken in the morning and in the afternoon. | ||
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The curves so calculated were loaded for all the video modes tables: */255, */128 and */0 (despite the latter seems not used at all). For photo modes I leaved a linear gamma (no transformation at all), because I prefer to do color balancing in post-processing. | The curves so calculated were loaded for all the video modes tables: */255, */128 and */0 (despite the latter seems not used at all). For photo modes I leaved a linear gamma (no transformation at all), because I prefer to do color balancing in post-processing. | ||
- | === Chroma curves === | + | As you can see from the following graphs, my custom gamma curves have just a little deviation from the **neutral 1.0 gamma**: |
+ | |||
+ | {{.: | ||
+ | {{.: | ||
+ | {{.: | ||
+ | |||
+ | The gamma curves of the **original 1.3.2 firmware** do instead **boost the image contrast** by darkening the shadows and brightening the highlights: | ||
+ | |||
+ | {{.: | ||
+ | {{.: | ||
+ | {{.: | ||
+ | |||
+ | ==== Chroma curves | ||
I think that the original chroma curves programmed into the SJ8 Pro are responsible for the over-saturated colors and for some annoying banding often visible in the blue sky. I changed the curves reducing smoothly the graph toward the highlights for the table */128 (used for evenly exposed parts of the image) and increasing smoothly the graph starting from the shadows for the table */0 (used for over-exposed parts of the image). Based on my testing the table */255 is responsible for very low chrominance applied only for heavy under-exposed images, so I leaved the original graph, which is a straight line all at the maximum value. | I think that the original chroma curves programmed into the SJ8 Pro are responsible for the over-saturated colors and for some annoying banding often visible in the blue sky. I changed the curves reducing smoothly the graph toward the highlights for the table */128 (used for evenly exposed parts of the image) and increasing smoothly the graph starting from the shadows for the table */0 (used for over-exposed parts of the image). Based on my testing the table */255 is responsible for very low chrominance applied only for heavy under-exposed images, so I leaved the original graph, which is a straight line all at the maximum value. | ||
- | === Sounds === | + | In the following images you can see my **custom chroma curves**: |
+ | |||
+ | {{.: | ||
+ | {{.: | ||
+ | {{.: | ||
+ | |||
+ | You can compare them with the **stock chroma curves**, from the **original 1.3.2 firmware**: | ||
+ | |||
+ | {{.: | ||
+ | {{.: | ||
+ | {{.: | ||
+ | |||
+ | As far I can understand, the original curves **%%*/ | ||
+ | |||
+ | ==== Sounds | ||
I changed the original sounds for **power-on**, | I changed the original sounds for **power-on**, | ||
- | === autoexec.ash === | + | ==== autoexec.ash |
The **autoexec.ash** file is not actually part of the firmware; if you want you can copy it into the root directory of the SD card. It is written in Ambarella Shell and it is executed at camera power on. | The **autoexec.ash** file is not actually part of the firmware; if you want you can copy it into the root directory of the SD card. It is written in Ambarella Shell and it is executed at camera power on. |
doc/appunti/hardware/sjcam-8pro-custom-firmware.txt · Last modified: 2023/06/09 07:38 by niccolo