When creating online video content, choosing the right color space is essential for achieving high quality and ensuring proper playback across different devices and platforms. The color space defines the range of colors that can be represented and determines how color information is encoded in the video file. With several options available, selecting the optimal color space for your project requires careful consideration of factors like intended delivery methods, target playback devices, and desired visual quality.
Key Color Spaces for Online Video
The three main color space choices for online video production and delivery are:
- RGB – The standard color space used for computer displays. RGB stands for the three primary colors red, green, and blue.
- YCbCr – Used for video compression and transmission. YCbCr represents color in terms of luma (brightness) and chroma (color).
- CIE 1931 xyY – An absolute color space defined by the International Commission on Illumination (CIE) based on human visual perception.
Here is a comparison of key attributes of these three color spaces:
| Color Space | Key Attributes |
|---|---|
| RGB |
|
| YCbCr |
|
| CIE 1931 xyY |
|
Factors to Consider
When selecting a color space for your online video project, the following factors should be taken into account:
Delivery Method
The way your video content will be delivered to viewers is a key consideration. For video streamed over the internet or social media, YCbCr is commonly used since it is optimized for compression and transmission. For video files downloaded for playback on local devices, RGB may provide the best quality and compatibility.
Target Playback Devices
The types of devices your audience will use to watch the videos should guide your color space choice. For content played primarily on televisions or mobile devices, YCbCr is likely the best option. But for videos watched mainly on computer displays, RGB may be preferable.
Compression Codecs
If you intend to compress your video files using a codec like H.264 or HEVC, using YCbCr will usually achieve better compression efficiency and quality. The color transform from RGB to YCbCr is built into these video codecs.
Visual Quality
For high end projects where visual quality is critical, RGB or a wide gamut color space may provide the best results. RGB has a larger color volume than YCbCr, providing more richness and depth to imagery.
Compatibility
The compatibility of your chosen color space across different software, codecs, and devices is important to consider. RGB enjoys broad compatibility given its long standing use for computer graphics and video. YCbCr is also widely supported by video processing software and playback devices.
Recommended Color Spaces
Taking into account the above factors, here are recommended color spaces for common online video delivery scenarios:
Streamed Internet/Social Media Video
For video consumed primarily via online streaming, YCbCr is the best choice. YCbCr provides good compression efficiency for streaming formats like MPEG-DASH and HLS. It’s also natively supported by both H.264 and HEVC codecs commonly used for online streaming. The separation of luma and chroma in YCbCr matches up with human visual perception, where we are more sensitive to brightness than color details. This allows chroma channels to be compressed more aggressively with minimal visual impact.
Downloaded Playback on TVs/Mobile Devices
If your videos will mostly be downloaded locally on televisions, smartphones and tablets, YCbCr is again the top choice. These playback devices are designed to work with YCbCr signals from video compression codecs. Using YCbCr ensures proper color space support across the video production and delivery chain.
Computer Display Playback
For video intended primarily for playback on computer monitors and desktop media players, RGB is likely the best option. Computer displays use RGB color, so keeping video content natively in RGB avoids extra color space conversions. RGB also avoids potential color shifts from converting to and from YCbCr. The larger color volume of RGB can provide more vivid and accurate colors compared to YCbCr on desktop playback.
High Visual Quality Productions
For professional video productions where visual quality is a top priority, RGB or a wide gamut color space like DCI-P3 should be considered. RGB and wide gamut color spaces preserve more color information from cameras and avoid clamping colors during color space conversions. This results in richer and more cinematic visuals. The downside is larger file sizes compared to YCbCr.
Converting Between Color Spaces
In many professional video workflows, multiple color spaces will be encountered through different stages like recording, editing, compression, and delivery. Proper color space management and conversion helps maintain color accuracy and prevent introduction of artifacts or color shift issues. Here are some tips on converting between color spaces:
- Use linear/gamma corrected color spaces – Color space conversions should happen between linear RGB spaces that don’t introduce gamma distortion.
- Employ high quality conversion – Dedicated color space conversion algorithms like those in OpenCV generally produce better results than quick conversions.
- Avoid multiple conversions – Converting through multiple color spaces can compound errors, so minimize conversions steps.
- Check histograms – View luma and chroma histograms before and after conversion to check for clipping or introduction of artifacts.
When properly handled, color space conversions can be transparent with no loss of quality. But careless conversion between color spaces can result in washed out or distorted colors in your videos.
Codec Color Space Support
If your workflow involves video compression through codecs like H.264, HEVC or ProRes, the codec’s color space capabilities must be taken into account. Here is how some common codecs handle color spaces:
H.264
- Main supported color spaces are YCbCr 4:2:0 8-bit and 10-bit
- Can also encode RGB and 4:4:4 chroma subsampled YCbCr
- Popular delivery codec for internet streaming and Blu-ray/AVCHD
HEVC
- Designed for 8-bit and 10-bit YCbCr 4:2:0 video
- Also supports 4:4:4, 4:2:2 chroma subsampling
- Offers improved compression over H.264
ProRes
- Apple ProRes supports RGB, YCbCr 4:2:2 and 4:4:4 color
- Higher color sampling than H.264 or HEVC
- Used for intermediate editing and production mastering
Understanding your delivery codec’s color space capabilities ensures your video can make it through compression cleanly and avoid any color space mismatches.
Broadcast Standards
For video destined for broadcast television, color spaces are defined by video standards like Rec. 709 HD and Rec. 2020 UHD. These specify color parameters like primaries, white point, gamma curve and bit depth. Adhering to broadcast color space standards guarantees your videos will display properly on consumer televisions.
Some key broadcast color spaces are:
- Rec. 709 – HDTV standard using YCbCr color with 16-235/240 luma range and 16-240 chroma range.
- Rec. 2020 – Ultra HD standard with wide gamut color and 10-bit sampling support.
- DCI-P3 – Digital cinema color space with deep greens/cyans and used for 4K content.
When creating video for television or cinema, consult broadcast guidelines to pick the correct color space and parameters.
Conclusion
Selecting the right color space is an important decision that will impact the quality, compatibility and compressibility of your online video content. While YCbCr is great for compression and streaming, RGB provides broader support for computer playback. For professional quality video, wider gamut color spaces preserve more color information. No single color space is best for all applications. Carefully weigh technical factors like delivery method, target devices, codecs and visual quality goals when choosing a color space tailored for your project needs.
