Bit depth explained: Impact on video, image, and audio quality

August 9, 2024
5 Min
Video Education
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What is Bit depth?

Bit depth, also known as color depth, defines the number of bits used to represent the color information of each pixel in a digital image or video. It's a key factor that influences the precision and quality of colors, shades, and overall visual clarity. In both video and audio, bit depth directly affects how detailed and smooth the output will appear or sound. A higher bit depth means richer color gradations, smoother transitions, and a broader range of brightness levels, offering a more immersive experience. This concept plays an equally vital role in audio, impacting the dynamic range and sound clarity.

In this blog, we will dive into the details of bit depth, exploring its significance in both video and audio, and why understanding this concept is essential for anyone working with digital media.

What is Bit Depth

What is Bit depth in video?

Same as image Bit depth in video too refers to the number of bits used to represent the colour of each pixel, which can directly affect the video's colour precision and detail. Higher bit depths in a video allow for more detailed colour representation, smoother gradients, and fewer instances of banding (banding is the visible horizontal or vertical lines that occur in an image or visual that can disrupt the visual quality).

Bit depth also enables videos to capture a broader range of brightness levels, enhancing detail in shadows and highlights. Bit depth isn’t just about the quality of the visual, but higher bit depths also provide better flexibility in post-production or editing.

Consider a live concert stream,

  • In Low bit depth (8-bit): The colors might appear slightly washed out, with visible banding in the audience lights or stage effects. The overall image quality might be grainy.
  • High bit depth (10-bit): The colors are vibrant and accurate, capturing the true atmosphere of the concert. The image is smoother, with finer details in the audience and on the stage.

In essence, bit depth directly impacts the visual quality of your live stream. While higher bit depth generally results in better quality, it also demands more bandwidth. So, finding the right balance between quality and efficiency is crucial for a successful live stream.

How to calculate bit depth of an image?

To calculate the bit depth of an image, you need to know the number of bits used to represent each pixel. The bit depth determines the number of colours or shades of grey that can be displayed in the image. Typically, each colour channel (red, green, blue) uses 8 bits, allowing 256 intensity levels per channel.

To find the total bit depth, you add up the bits for all colour channels. For example, with 8 bits per channel, the total bit depth would be 24 bits per pixel, known as 24-bit colour or "true colour." Some images may have an additional alpha channel for transparency, which uses another 8 bits, resulting in a 32-bit depth.

For grayscale images, the bit depth is determined by the number of bits used to represent the intensity of each pixel, commonly 8 bits (256 shades of grey) or 16 bits (65,536 shades of grey). The number of colours or shades that can be represented is equal to 2 raised to the power of the bit depth.

How to increase Bit depth?

Increasing the bit depth of video and audio enhances their quality and detail. For video, use higher bit depth cameras to capture more colour information or employ post-processing software like Adobe Premiere Pro or DaVinci Resolve to convert existing footage to a higher bit depth.

Conversion tools such as FFmpeg can also be used to increase bit depth, although this is limited by the original quality.

For audio, record with equipment that supports higher bit depths, like 24-bit or 32-bit float recorders, and use digital audio workstations (DAWs) such as Pro Tools or Logic Pro for editing. Tools like Audacity can convert existing audio files to a higher bit depth.

While increasing bit depth can enhance quality, it cannot add information that wasn’t originally captured, and it results in larger file sizes. Ensuring compatibility with playback devices and software is also crucial.

Colour representation and Bit depth

In digital imaging, each pixel's colour is typically represented by a combination of the primary colours: red, green, and blue (RGB). The bit depth determines how many discrete values each colour channel can have.

Smoother gradients

Smoother gradients are achieved by increasing the bit depth because the transition between colours becomes more gradual and less noticeable. With a lower bit depth, there are fewer discrete colour values, leading to noticeable "banding" where the transitions between colours are abrupt. Higher bit depths provide more intermediate colours, resulting in smoother transitions and eliminating visible banding.

8-bit vs 10-bit vs 12-bit

Let us see the difference between all the bits and their applications.

                                                                                                                                                                                                                                                   
Bit Depth Colour Precision Total Colours Common Application
8-bit256 shades per RGB channelApprox 16.7 million coloursGeneral-purpose video content (e.g., TV shows, movies, YouTube videos) Most consumer-grade digital cameras and smartphones
10-bit1,024 shades per RGB channel 1.07 billion colours High dynamic range (HDR) video professional video production and post-production. Broadcast television and streaming services
12-bit4,096 shades per RGB channelOver 68 billion colours Highest-end digital cinema and film production. Advanced medical imaging and scientific visualization. Specialized broadcast and post-production equipment.

Balancing Bit depth in video streaming: when to use high or low

Bit depth plays a important role in video streaming, impacting both visual quality and file size. Here's how to determine when to opt for high or low bit depth and how to strike the right balance.

When to use high Bit depth

High-Quality Content: For premium content like 4K or HDR videos, where color accuracy and detail are crucial, high bit depth ensures richer colors and finer gradations.

Post-Production: If extensive color grading or editing is involved, higher bit depth provides greater flexibility and precision, allowing for more detailed adjustments without compromising quality.

Target Audience with High-End Devices: Viewers using high-resolution displays and fast internet connections can fully appreciate the enhanced detail and depth provided by high bit depth.

When to use low Bit depth

Bandwidth Constraints: For mobile devices or users with limited internet access, lower bit depth can help reduce buffering and manage data usage, ensuring smoother playback.

Live Streaming: In real-time streaming scenarios, lower bit depth often facilitates faster processing and smoother delivery, crucial for maintaining stream continuity.

Content with Limited Color Variation: For videos with minimal color diversity, such as news broadcasts or documentaries, high bit depth may offer little additional benefit, making lower bit depth a more efficient choice.

What is Bit depth in audio?

In image bit-depth means the number of bits used to indicate the colour. With audio, it determines the resolution of each sample, directly influencing dynamic range and signal-to-noise ratio (SNR). It gives the number of bits used to encode each audio sample, with higher bit depth allowing for better sound quality.
Imagine a live hard rock concert. The music is characterized by heavy guitars, pounding drums, and powerful vocals.

  • Low bit depth (e.g., 8-bit): The recording would struggle to capture the full intensity of the music. The powerful guitar riffs might sound harsh or distorted, and the subtle nuances in the drumming and vocals would be lost. The overall sound would be compressed and lacking in depth.
  • High bit depth (e.g., 24-bit): This allows for a much more accurate representation of the concert experience. The crushing guitar chords, thunderous drums, and soaring vocals would be reproduced with incredible detail and impact. You'd be able to hear the individual strings on the guitar, the precise attack of the drumsticks, and the nuances of the vocalist's performance.

Just like a higher bit depth in an image captures more colors, a higher bit depth in audio captures a wider range of sound, allowing for a richer, more dynamic listening experience.

Does Bit depth affect sound quality?

Bit depth plays an important role in impacting the quality of an audio. Higher bit depths provide more detail and dynamic range, capturing both subtle and loud sounds with greater clarity. This results in clearer and better sound; however, lower bit depth may have quality distraction and might not be ideal for whoever is listening to the audio.

What is sample rate and Bit depth?

Sample rate and bit depth are two elements for producing audio. A sample rate is the number of samples of audio carried per second, measured in Hz.. It determines the frequency range that can be captured in the audio signal. Common sample rates include 44.1 kHz (used in CDs), 48 kHz (standard for digital audio), and higher rates like 96 kHz or 192 kHz (used in high-resolution audio), whereas a bit depth refers to the number of bits of information in each sample of audio data.  

It defines the dynamic range and resolution of the audio signal. Common bit depths are 16-bit (CD quality), 24-bit (standard for digital recording), and sometimes 32-bit (used in professional audio workstations).

Conclusion

Bit depth determines the quality of a video. For video, higher bit depths mean more colour gradations and better contrast. In audio, increased bit depth means greater dynamic range and reduced distortion. The different bits, such as 8 bits, 10 bits, and 12 bits, all hold a different application, which is why a clear understanding of bit depth is important for creating better and smoother videos and audio.

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