Conversion causes only red text to be smeared?

[InvisibleMan]

I used the following command to convert a video from uncompressed+PCM to WMV+WMA:
ffmpeg -i test_group_6.uncompressed.avi -vcodec wmv2 -sameq -acodec wmav2 -f asf test_group_6.asf

It seems as though only red text is smeared, leaving the rest of the video sharp.

These are the only codec packs that are installed that I know of:
CamStudio Lossless
DivX (the problem was happening before this one was installed).

I also had ffdshow installed, but uninstalling it did not solve the problem.

Uncompressed: http://www.ifthensoftware.net/invisibleman/test_group_6.uncompressed.avi.zip (39.8MB)
Compressed: http://www.ifthensoftware.net/invisibleman/test_group_6.asf (6.83 MB)

Any thoughts on what might be causing this problem?

[jagabo]

All high compression codecs encode colors with less resolution than the grayscale portion of the image. For example, a 720x480 frame will the grayscale portion of the image encoded at 720x480 but the color channels encoded at 360x240. Small colored text will get blurry.

Normally I'd recommend you use bigger text or use similar colors for the text and background with different intensities. But since you are recording gameplay there's probably not much you can do. One thing you can try: before encoding, shift the frame up one scanline. That might align the low res color better with the luma channel.

[InvisibleMan]

The dark blue text on the dark background (about 2 seconds in) didn't get affected though... Is this because the text and the background are both dark?

[jagabo]

The dark blue text is effected the same way. It's just harder to see. Different renderers stretch the low res chroma channels differently so exactly what you see may vary. But here's are 4x nearest neighbor enlargements (so you can see each pixel easily) of the original (left) and two different renderers (center, right):


[Attachment 1654 - Click to enlarge]

[InvisibleMan]

All right, thanks for the information.