Transrating
Transrating is the process of changing a video's bitrate while keeping the same codec and, usually, the same resolution. A 10 Mbps H.264 stream might be transrated to 4 Mbps H.264 so it fits a slower network. Transrating is a narrow form of transcoding focused only on data rate.
Why it matters
Transrating lets a business fit video into a fixed amount of network or broadcast capacity without the full cost of transcoding. It helps operators carry more channels, and helps streamers offer a lighter version of a stream for slower connections. The tradeoff is that lowering bitrate always lowers picture quality to some degree.
How it works
- The system reads an existing compressed stream and keeps its codec and usually its resolution.
- It recalculates how much data each frame can use to hit a lower target bitrate.
- It re-quantizes the picture, meaning it stores detail less precisely, to cut the data rate.
Transrating vs transcoding: what is the difference?
Transrating changes only the bitrate, while transcoding can change the codec, resolution, frame rate and bitrate. Transrating is a narrow type of transcoding. It is useful when the target devices already support the codec but the network cannot carry the original data rate. If the codec or picture size also has to change, a full transcode is needed.
Does transrating reduce video quality?
Yes, transrating reduces quality because the same picture is stored with less data. How visible the loss is depends on the content and how far the bitrate drops. Calm scenes can lose a lot of bitrate with little visible change. Fast sports or busy scenes show blockiness sooner when bitrate is cut too far.
Where it's used
Pay-TV operators and broadcasters transrate channels to fit more of them into fixed cable or satellite capacity, giving subscribers a wider lineup without a full re-encode.
