DM355 OSD transparency problem

OSD1 hardware window is configured by software as attribute window used for blending purposes by default.  The way this attribute window controls the blending between the data present in the video windows and OSD0 window is by allowing each nible (4-bits) in this window to define the blending for a single pixel of OSD0, with allowed values between 0 and 7 (providing only 8 possible levels of blending); even though only 3-bits of the nible are used to support the 8 levels of blending, nibles were chosen for hardware data alignment reasons.   The blending works as follows

   value = 0  (hex 0x0) --> 100% video, 0% OSD

   .......

   value = 3  (hex 0x3) --> 50% video, 50% OSD

.......

   value = 3  (hex 0x3) --> 0% video, 100% OSD

Therefore the 33s you are seeing in the binary editor are the nibles corresponding to the pixels that are 50% video and 50% OSD; the FFs you are seeing are the nibles corresponding to pixels that are 100% OSD and 0% video.  That said, if you have more nibles defined in the .attr file than number po pixels being displayed, not all nibles in attr file may be being used by attribute window (e.g. maybe only the 33s).  Therefore, keep in mind that the attr window size needs to be the resolution of the video being displayed (720x480) devided by 2 since we are using nibles (2 nibles per byte).

Hope this helps.