Does JPEG Encoder on DM365 supports Gray JPEG Encoding?

Specifically speaking about JPEG codec, if you want JPEG codec to convert a color image into a grayscale image and then compress it, I do not believe JPEG support this.  If you already have a gray image and you want JPEG encoder to compress it, then this should certainly be possible.  One scenerio that comes to mind is chossing YCbCr input where only the Y values are input (e.g. temporarily disconnect Cb and Cr Cables from input source); this will produce a gray image (Y-Luma component only) wich can be captured into DDR2 and encoded via JPEG encoder..

Kenzo said:

can JPEG encoder on DM365 supports Gray input undocumented?

If the manual says it cannot than I am afraid it cannot, the JPEG encoder on this and other devices was designed to handle color formatted data from the ground up, and in this case it is using a JPEG hardware accelerator that is not very flexible. If you wanted a JPEG encoder that supported gray input natively than you would probably have to use a software based solution on the ARM (which would probably be slower than using the accelerator with a color image). I think you may also run into compatibility issues with decoding the JPEG at the other end if you were encoding it in pure gray, my understanding is that a standard JPEG decoder will be expecting the contents to be in a YCbCr 4:2:2 format, so I suspect some decoders might get confused if the image was a contiguous gray image. On the other hand I suppose an encoder that supported gray input could encode in a YCbCr 4:2:2 format and just fill in the Cb/Cr data with a blank (average) value as Juan was suggesting and still gain speed by not processing on them, but this still requires a different encoder to gain the performance, unfortunately I am not that familiar with grey input JPEG encoders.