DeInterlacer, Double Buffering and Stalling Behavour

[Altera_Forum]

Hi, 

 Does anybody know what the de-interlacer, using double buffering and the weave algorithm, will do when the output is stalled long enough so that the input has finished the current input buffer and requires the buffers to be swopped, but the output is not yet done reading out the data from the output buffer? Does it force a buffer swop (i.e. the remainder of the output will be from the new output buffer) or does it drop the frame in the input buffer and start again, allowing the output buffer to finish readout?    I know tripple buffering has the ability to drop or repeat frames, but I need to use double buffering.    I know I could could go and instantiate one and simulate it to see what happens, but maybe someone knows this of his/her head...   Thanks, Niki

[Altera_Forum]

Hi, 

 When using double buffering, the deinterlacer will never drop incoming fields unless there is something unexpected with the input stream (eg, a change of resolution, two consecutive F0 fields, ...). When the input has filled the current input buffer, it has to wait for the output to be ready to perform a swap. Consequently, if back-pressure is applied at the output for a long period of time then the input will also start to apply back-pressure a while later.  vgs

[Altera_Forum]

The double buffering will only handle minor mismatches in phase (like up to the vertical blanking time) and will not handle mismatches in frequency. 

 Jake

[Altera_Forum]

Hi vgs, 

 Thanks - makes perfect sense.   Regards, Niki