Bitrate - Everything You Need To Know

Definition

Video bitrate refers to the amount of data processed per unit of time in a video stream, typically measured in bits per second (bps). It determines the video's quality and file size, with higher bitrates generally indicating better quality and larger file sizes. Bitrate can be variable or constant, affecting video compression efficiency and playback smoothness.

What does it really mean?

Video bitrate can be likened to the flow of water through a hose. The bitrate is analogous to the water flow rate; a higher flow rate (higher bitrate) means more water (more data) is delivered per second, leading to a fuller, more forceful stream (higher video quality). Conversely, a lower flow rate (lower bitrate) results in less water per second, leading to a weaker stream (lower video quality). Just as the size and length of the hose can affect water flow and pressure, factors like video compression and file size are impacted by the bitrate.

How does bitrate affect video quality?

1. Detail and Clarity: A higher bitrate allows for more data per second to be captured and processed, resulting in better detail and clarity in the video. This is particularly noticeable in scenes with high motion or complexity, where a low bitrate might result in blurring or artifacts.
2. Compression Artifacts: Videos with lower bitrates are more heavily compressed to reduce file size, which can lead to compression artifacts. These artifacts manifest as pixelation, blockiness, and blurring, especially in fast-moving or complex scenes.
3. Resolution and Frame Rate: While bitrate is not the same as resolution or frame rate, it is closely related. A higher resolution or frame rate usually requires a higher bitrate to maintain quality. If the bitrate is too low for a high-resolution video, the quality will suffer.
4. Color Depth and Contrast: Higher bitrates can better handle nuances in color and contrast, leading to a richer and more vibrant visual experience. Lower bitrates might result in washed-out or flat colors.
5. Smooth Playback: Adequate bitrate is essential for smooth playback. A bitrate too low for the video's resolution and frame rate can result in stuttering or buffering issues.

Best Bitrate for Live Streaming

Facebook

Aspect	Specification
Resolution	1080p (1920 x 1080)
Frames Per Second	30 fps
Bitrate Range	3,000-6,000 Kbps
Keyframe	2 seconds
Video Codec	H.264, Level 4.1
Time Limit	8-hour
Audio Sample Rate	44.1 kHz
Audio Channel	Stereo
Audio Bitrate	128 Kbps

Twitch

NVIDIA NVENC Specs:

Resolution	Frame Rate	Bitrate (kbps)	Rate Control	Keyframe Interval	Preset	B-frames
1920x1080 (1080p)	60 or 50 fps	6000	CBR	2 seconds	Quality	2
1920x1080 (1080p)	25 or 30 fps	4500	CBR	2 seconds	Quality	2
1280x720 (720p)	60 or 50 fps	4500	CBR	2 seconds	Quality	2
1280x720 (720p)	25 or 30 fps	3000	CBR	2 seconds	Quality	2

x264 Specs:

Resolution	Frame Rate	Bitrate (kbps)	Rate Control	Keyframe Interval	Preset	Profile
1920x1080 (1080p)	60 or 50 fps	6000	CBR	2 seconds	veryfast <-> medium	Main/High
1920x1080 (1080p)	25 or 30 fps	4500	CBR	2 seconds	veryfast <-> medium	Main/High
1280x720 (720p)	60 or 50 fps	4500	CBR	2 seconds	veryfast <-> medium	Main/High
1280x720 (720p)	25 or 30 fps	3000	CBR	2 seconds	veryfast <-> medium	Main/High

Youtube

Ingestion Resolution / Frame Rate	Minimum Bitrate Setting (Mbps)	Maximum Bitrate Setting (Mbps)
4K / 2160p @ 60fps	10	40
4K / 2160p @ 30fps	8	35
1440p @ 60fps	6	30
1440p @ 30fps	5	25
1080p @ 60fps	4	10
1080p @ 30fps	3	8
720p @ 60fps	3	8
240p - 720p @ 30fps	3	8

YouTube Encoder Settings:

Aspect	Specification
Protocol	RTMP/RTMPS Streaming
Video Codec	H.264, H.265 (HEVC), AV1
Frame Rate	Up to 60 fps
Keyframe Frequency	Recommended 2 seconds (Do not exceed 4 seconds)
Audio Codec	AAC or MP3 (5.1 surround sound audio is only supported for AAC in RTMP)
Bitrate Encoding	CBR
Pixel Aspect Ratio	Square
Frame Types	Progressive Scan, 2 B-Frames, 1 Reference Frame
Entropy Coding	CABAC
Audio Sample Rate	44.1 KHz for stereo audio, 48 KHz for 5.1 surround sound
Audio Bitrate	128-Kbps for stereo or 384 Kbps for 5.1 surround sound
Color Space	Rec. 709 for SDR

Frequently Asked Questions

What bitrate is good quality?

Good quality video typically requires a bitrate of around 3,000 to 6,000 Kbps (3-6 Mbps) for 1080p resolution. However, higher resolutions like 4K may need bitrates upwards of 15,000 to 35,000 Kbps (15-35 Mbps) for optimal quality.

How to calculate bitrate?

Bitrate is calculated by multiplying the video's frame size by the frame rate and the bit depth, then factoring in compression efficiency. It's typically expressed in bits per second (bps) or kilobits per second (kbps).

What is bitrate per resolution?

Bitrate per resolution refers to the amount of data processed per second for a given video resolution, with higher resolutions generally requiring higher bitrates. For instance, 1080p video might need 3,000 to 6,000 Kbps, while 4K resolution often requires over 15,000 Kbps for good quality.

References

• https://help.twitch.tv/s/article/broadcasting-guidelines?language=en_US
• https://www.facebook.com/help/1534561009906955?helpref=faq_content
• https://support.google.com/youtube/answer/2853702?hl
• https://en.wikipedia.org/wiki/Bit_rate
• https://www.khanacademy.org/computing/computers-and-internet/xcae6f4a7ff015e7d:the-internet/xcae6f4a7ff015e7d:connecting-networks/a/bit-rate-bandwidth-and-latency