Field stepping

I'm not coming up with a good way to do field stepping with the deinterlace filter.

If you do playctrl.NextFrame() when paused it will take you to the next frame rather than the next field (so skips every other field).

If you play very slowly (say 1/50) and monitor the frame times, one frame is presented more or less at the right time but the second frame is timed just after - say 0.2ms after. This presumably would make it very hard to step by time rather than frame/field.

I've tested with a variety of interlaced sources, all with the same behaviour.

I would be happy even if I could get both fields somehow at once and manually select as appropriate.

Any ideas?

Thanks, Joe

Joe,
When using the de-interlace filter, the output of the filter will be the 2 split half frames for each input frame. However, seeking is done before the filter at the splitter (demultiplexer) and video decoder side. This means seeking will always take place at the interlaced full frames side, not the split half-frames side.

There could be an indirect way to solve it as follows:
1. Use the LEAD Video Callback filter instead of the De-interlace filter. This filter gives you the pixel data for each frame.
2. Perform your own splitting of this data.
3. When using this filter, you can get accurate frame seeking if you use the CurrentFramePosition (which seeks in frames) instead of CurrentPosition (which seeks in seconds). You can then get the frame, split it, and draw the half frame you choose.

One drawback is that you will have to implement both your own splitting and your drawing code. This means you won't be using our ltmmPlay control for displaying the split half-frames.

Its something I could do as I'm already using the callback filter because I want to have more control over the drawing anyway. I just didn't want to write my own deinterlacing code.

Thanks, Joe