An image transmission system mounted on a vehicle, comprising a camera that acquires a surrounding image as an original image, an image transmitting device, an image receiving device having an image recognition unit, and an on-board network, the image transmitting device and the image receiving device being coupled to each other so as to communicate with each other via the on-board network, the image transmitting device comprising: an image encoding device for receiving the original image and generating image encoding data by encoding the original image according to an encoding parameter, the image transmitting device being adapted to supply an image encoding stream including the image encoding data and the encoding parameter to the image receiving device, the encoding parameter being at least one of a parameter indicating whether to use the deblocking filter for the image encoding data, a filter coefficient of the deblocking filter, and a quantization parameter for quantization included in encoding for generating the image encoding data, the image receiving device comprising: a data receiving unit for receiving the image encoding stream, a parameter changing unit configured to change the encoding parameter in the image encoding stream received by the data receiving unit such as to increase accuracy of image recognition performed by the image recognition unit, a decoding unit, including a deblocking filter and an inverse quantization unit, for generating image decoding data as a decoded image, by decoding the image encoding stream including the image encoding data received by the data receiving unit and the parameter changed by the parameter changing unit using the encoding parameter changed by the parameter changing unit as a decoding parameter, and the image recognition unit for performing the image recognition on the image decoding data, wherein the parameter changing unit is further adapted to change, according to a running condition of the vehicle and/or environmental information of the vehicle, the encoding parameter received by the data receiving unit. an image encoding device for receiving the original image and generating image encoding data by encoding the original image according to an encoding parameter, the image transmitting device being adapted to supply an image encoding stream including the image encoding data and the encoding parameter to the image receiving device, the encoding parameter being at least one of a parameter indicating whether to use the deblocking filter for the image encoding data, a filter coefficient of the deblocking filter, and a quantization parameter for quantization included in encoding for generating the image encoding data, the image receiving device comprising: a data receiving unit for receiving the image encoding stream, a parameter changing unit configured to change the encoding parameter in the image encoding stream received by the data receiving unit such as to increase accuracy of image recognition performed by the image recognition unit, a decoding unit, including a deblocking filter and an inverse quantization unit, for generating image decoding data as a decoded image, by decoding the image encoding stream including the image encoding data received by the data receiving unit and the parameter changed by the parameter changing unit using the encoding parameter changed by the parameter changing unit as a decoding parameter, and the image recognition unit for performing the image recognition on the image decoding data, wherein the parameter changing unit is further adapted to change, according to a running condition of the vehicle and/or environmental information of the vehicle, the encoding parameter received by the data receiving unit. a data receiving unit for receiving the image encoding stream, a parameter changing unit configured to change the encoding parameter in the image encoding stream received by the data receiving unit such as to increase accuracy of image recognition performed by the image recognition unit, a decoding unit, including a deblocking filter and an inverse quantization unit, for generating image decoding data as a decoded image, by decoding the image encoding stream including the image encoding data received by the data receiving unit and the parameter changed by the parameter changing unit using the encoding parameter changed by the parameter changing unit as a decoding parameter, and the image recognition unit for performing the image recognition on the image decoding data, wherein the parameter changing unit is further adapted to change, according to a running condition of the vehicle and/or environmental information of the vehicle, the encoding parameter received by the data receiving unit.