Bitrate and Bandwidth for Video

Bitrate and Bandwidth for Video

Bitrate is the amount of data used to store each second of video. It is measured in megabits per second for video streams and megabytes per second for file sizes. Higher bitrate means more data per second, which translates to better image quality, less compression artifacts, and more detail. Lower bitrate means smaller files but lower quality with visible artifacts in areas of fine detail or motion.

Bitrate is directly related to resolution, frame rate, and codec efficiency. A 4K video at 24 fps needs roughly four times the bitrate of a 1080p video at the same frame rate and codec to maintain the same quality per pixel. Higher frame rates also require proportionally higher bitrates. Different codecs achieve different efficiency levels. H.265 can deliver the same quality as H.264 at roughly half the bitrate, but requires more processing power to encode and decode.

Variable bitrate and constant bitrate are two different approaches to encoding. Constant bitrate uses the same amount of data for every second of video. This is predictable and required for live streaming and broadcast, but it wastes data on simple scenes and may not allocate enough data for complex scenes. Variable bitrate allocates more data to complex scenes and less to simple ones, achieving better overall quality for the same file size. Variable bitrate is preferred for file-based delivery.

Calculating storage requirements is straightforward once you know the bitrate. A video at 50 megabits per second is 6.25 megabytes per second. Multiply by 60 for 375 megabytes per minute, or about 22 gigabytes per hour. For ProRes 422 HQ at 4K, the bitrate is roughly 750 megabits per second, which works out to about 5.6 gigabytes per minute. This is why high quality video projects require large amounts of fast storage.

Bandwidth refers to the data transfer capacity of your connection or storage device. When editing video, your storage needs to deliver data faster than the video's bitrate. A 4K ProRes file with a bitrate of 750 Mbps requires storage that can read at over 90 megabytes per second sequentially. Most modern SSDs handle this easily, but older hard drives or network storage may struggle. For smooth editing, your storage should be at least twice as fast as the video bitrate demands.