Pic-Video 3 MJPEG codec and Virtual Dub Question

[mcpogue]

Hi,

When configuring the Pic-Video MJPEG codec for capture, my "Encode Normalized YUV" box is checked...should I also check "squish luminance range" in Virtualdub's video menu? Should they both be enabled or should it be one or the other? If so which? Does it matter?

Also is there a good guide or tutorial for understanding colorspaces?

[mcpogue]

No replies? (

[mcpogue]

Did I ask a dumb question, or post to the wrong forum?

[SLK001]

I don't know what "squish luminance range" means. What does the VirtualDUB HELP files say about that? Does it mean adjust the luminance values to NTSC range (16-235)?

The YUV is just the colorspace selector. You can use YUV or, if available, YV12 is native DVD.

Anyway, if you don't get the answers you need, just start experimenting to see what works best for your application.

[mcpogue]

>>Does it mean adjust the luminance values to NTSC range (16-235)? <<

Yes, that's what "squish luminance range" does...what I'm trying to figure out is: the codec has a "Encode Normalized YUV" setting. Here's what pic-video's helpfile says:

This setting controls how YUV input to the compressor is encoded. Many M-JPEG codecs (including previous versions of PICVideo) have treated YUV input to the compressor as though luminance and chrominance values are in the range of 0 to 255.

However, the actual YUV input to the compressor has luminance and chrominance values which are in the range 16 to 235 and 16 to 240 respectively.

The result of encoding YUV incorrectly is that the resulting video can look washed out and undersaturated.

By enabling this setting, PICVideo will correctly encode normalized YUV and will also add a “PICAVI” APP1 marker to each frame or field, marking the frame or field as properly encoded.

If this setting is not enabled, RGB will be encoded correctly during compression but YUV will not be encoded correctly and the “PICAVI” APP1 marker will not be written to each frame or field.

Range: true, false

Default: unchecked (false)

Is this setting redundant, or do both need to be enabled? Sounds to me like that checkbox simply tells the codec to "expect" values from 16-235 and encode accordingly...unchecked would mean expect input to the compressor of 0-255. I just want to make sure I'm reading that correctly.

[SLK001]

It depends on what format you are capturing. If you are NTSC, then use the 16-235 LUMINANCE setting and the 16-240 CHROMINANCE settings.