An encoder comprising: an encoding module configured to encode video in at least one region-of-interest and outside the region-of-interest, the encoding comprising quantization and the encoding module being operable to apply a difference in quantization step between the encoding inside and outside the region-of-interest; and an adaptation module configured to determine a metric and to perform adaptation dependent on the at least one metric, wherein the adaptation module is configured to adapt the difference in quantization step in dependence on the at least one metric, wherein the metric is a measure of the bitrate incurred by encoding in the region-of-interest compared to the bitrate incurred by encoding outside the region-of-interest; the encoder being characterised in that: wherein the determination of the at least one metric comprises determining whether the bitrate incurred in the region-of-interest is above a target amount greater than the bitrate incurred outside the region-of-interest, and wherein the adaptation module is configured to decrease the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is above the target, and/or to increase the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is below the target. an encoding module configured to encode video in at least one region-of-interest and outside the region-of-interest, the encoding comprising quantization and the encoding module being operable to apply a difference in quantization step between the encoding inside and outside the region-of-interest; and an adaptation module configured to determine a metric and to perform adaptation dependent on the at least one metric, wherein the adaptation module is configured to adapt the difference in quantization step in dependence on the at least one metric, wherein the metric is a measure of the bitrate incurred by encoding in the region-of-interest compared to the bitrate incurred by encoding outside the region-of-interest; the encoder being characterised in that: wherein the determination of the at least one metric comprises determining whether the bitrate incurred in the region-of-interest is above a target amount greater than the bitrate incurred outside the region-of-interest, and wherein the adaptation module is configured to decrease the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is above the target, and/or to increase the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is below the target. wherein the determination of the at least one metric comprises determining whether the bitrate incurred in the region-of-interest is above a target amount greater than the bitrate incurred outside the region-of-interest, and wherein the adaptation module is configured to decrease the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is above the target, and/or to increase the difference in quantization step on condition of detecting that the bitrate inside the region-of-interest is below the target.