Processing display data for transmission

A method of decompressing compressed display data at a client device, the method comprising:

• receiving, from a host device, compressed display data;
• determining whether the received compressed display data comprises only a general approximation coefficient, or whether the received compressed display data comprises the general approximation coefficient and at least one detail coefficient for a group of pixels to be displayed, the general approximation coefficient and the at least one detail coefficient having been obtained using a wavelet transformation of the group of pixels;
• if it is determined that the received compressed display data comprises only the general approximation coefficient, retrieving at least one detail coefficient previously received from the host device and stored at the client device;
• and
• decompressing the compressed display data using the general approximation coefficient and the retrieved at least one detail coefficient to produce pixel values of pixels in the group of pixels to be displayed.

A host device configured to:

• receive pixel values for a group of pixels in an image frame of display data;
• perform a wavelet transformation on the group of pixels to obtain a general approximation coefficient and a plurality of detail coefficients for the group of pixels;
• determine whether to prioritise transmission of the general approximation coefficient over transmission of the detail coefficients to the client device based on whether there are sufficient resources available to enable the image frame to be ready for display by the client device and/or based on a time since the detail coefficients for a corresponding group in a previous frame were previously transmitted to the client device;
• and
• in response to determining to prioritise transmission of the general approximation coefficient over transmission of the detail coefficients:
• transmit only the general approximation coefficient to the client device, or
• compress at least one detail coefficient so as to be more compressed than the general approximation coefficient and transmit the general approximation coefficient and the at least one compressed detail coefficient to the client device.

A client device configured to:

• receive, from a host device, compressed display data;
• determine whether the received compressed display data comprises only a general approximation coefficient, or whether the received compressed display data comprises the general approximation coefficient and at least one detail coefficient for a group of pixels to be displayed, the general approximation coefficient and the at least one detail coefficient having been obtained using a wavelet transformation of the group of pixels;
• if it is determined that the received compressed display data comprises only the general approximation coefficient, retrieve at least one detail coefficient previously received from the host device and stored at the client device;
• and
• decompress the compressed display data using the general approximation coefficient and the retrieved at least one detail coefficient to produce pixel values of pixels in the group of pixels to be displayed.

A system comprising:

• a host device configured to:
• receive pixel values for a group of pixels in an image frame of display data;
• perform a wavelet transformation on the group of pixels to obtain a general approximation coefficient and a plurality of detail coefficients for the group of pixels;
• determine whether to prioritise transmission of the general approximation coefficient over transmission of the detail coefficients to the client device based on whether there are sufficient resources available to enable the image frame to be ready for display by the client device and/or based on a time since the detail coefficients for a corresponding group in a previous frame were previously transmitted to the client device;
• and
• in response to determining to prioritise transmission of the general approximation coefficient over transmission of the detail coefficients:
• transmit only the general approximation coefficient to the client device, or
• compress at least one detail coefficient so as to be more compressed than the general approximation coefficient and transmit the general approximation coefficient and the at least one compressed detail coefficient to the client device;
• and
• a client device configured to:
• receive, from the host device, compressed display data;
• determine whether the received compressed display data comprises only a general approximation coefficient, or whether the received compressed display data comprises the general approximation coefficient and at least one detail coefficient for a group of pixels to be displayed, the general approximation coefficient and the at least one detail coefficient having been obtained using a wavelet transformation of the group of pixels;
• if it is determined that the received compressed display data comprises only the general approximation coefficient, retrieve at least one detail coefficient previously received from the host device and stored at the client device;
• and
• decompress the compressed display data using the general approximation coefficient and the retrieved at least one detail coefficient to produce pixel values of pixels in the group of pixels to be displayed.