Friday, June 7, 2013

Does the Raspberry Pi cut off the left and right sides when in TV-out mode?

The topic says it all. Does it, or doesn't it? I whipped up a quick test video (played a quick 15 seconds of Left 4 Dead in order to get a source that had no artifacts in it) and made some comparisons.

Original image rendered from the game and cropped by me:

Converted to .ldimg file, and rendered (using composite NTSC) by Raspberry Pi:
Now let's examine one place:

Here is the original.  Notice the border on the right side is dark green with a grey patch of a zombie's shirt.

Here is the pi version.  It's a little hard to tell, but the right side is completely black and the grey patch from the zombie's shirt is nowhere to be seen.


The pi does not shrink a source 720x480 image but instead overwrites the left and right borders with black.  This means that discs that are captured in 720x480 should be re-encoded "as is" without getting rid of the black borders.

1 comment:

  1. This can be considered "normal" behavior. The visible part of a scanline is only 704 pixels wide, so there should be 8 pixels of black on each side.

    Laserdiscs and players don't always match this exactly, so there may be cases where we'd want to shift the image left or right to avoid losing pixels. We definitely don't want to stretch it to fit 720, though.

    This is outside of the "safe area" that actually shows on-screen, and stretching vs. not stretching is a smaller difference than the variation in horizontal width settings on different monitors, so this isn't critical either way. :)