Secure decoder and secure decoding methods

A method comprising reading, from a secure memory via a secure channel, a decrypted decoded rendition of a base layer of a video signal, wherein the decrypted decoded rendition of the base layer has a first resolution;

• reading, from an unsecure memory, a decoded rendition of an enhancement layer of the video signal, wherein the decoded rendition of the enhancement layer has a second resolution, wherein the second resolution is higher than the first resolution, and wherein the enhancement layer comprises a residual map obtained from a difference between an original rendition of the video signal and a reconstituted rendition generated by upsampling the base layer;
• generating an upsampled decrypted decoded rendition of the base layer of the video signal by upsampling the decrypted decoded rendition of the base layer such that the upsampled decrypted decoded rendition of the base layer has the second resolution;
• applying the decoded rendition of the enhancement layer to the upsampled decrypted decoded rendition of the base layer to generate an output plane;
• and
• outputting the output plane, via the secured channel, to the secure memory for storage in the secure memory, wherein the output plane is for use in outputting by an output module to a display.

A non-transitory computer readable medium comprising computer program code configured to cause a processor to perform the following:

• read, from a secure memory via a secure channel, a decrypted decoded rendition of a base layer of a video signal, wherein the decrypted decoded rendition of the base layer has a first resolution;
• read, from an unsecure memory, a decoded rendition of an enhancement layer of the video signal, wherein the decoded rendition of the enhancement layer has a second resolution, wherein the second resolution is higher than the first resolution, and wherein the enhancement layer comprises a residual map obtained from a difference between an original rendition of the video signal and a reconstituted rendition generated by upsampling the base layer;
• generate an upsampled decrypted decoded rendition of the base layer of the video signal by upsampling the decrypted decoded rendition of the base layer such that the upsampled decrypted decoded rendition of the base layer has the second resolution;
• apply the decoded rendition of the enhancement layer to the upsampled decrypted decoded rendition of the base layer to generate an output plane;
• and
• output the output plane, via the secured channel, to the secure memory for storage in the secure memory, wherein the output plane is for use in outputting by an output module to a display.