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Old 15th April 2004, 19:00   #21  |  Link
Richard Berg
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It stores them the same. Different filters are free to interpret it in different ways.
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Old 16th April 2004, 14:56   #22  |  Link
sh0dan
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@LigH: since AviSynth cannot know if any given source is interlaced or not, all conversion have the "interlaced=true/false" flag.

For most filters interlaced/non-interlaced doesn't matter. If you have interlaced material, a SeparateFields() will give you progressive chroma placement anyway.

I tried doing chroma upsampling based on whether each separate frame was interlaced or not for teleconed material, and found that it lead to chroma shimmering.
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Old 16th April 2004, 15:27   #23  |  Link
LigH
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I still don't get it...

Let's assume progressive material, encoded as progressive MPEG2. If MPEG2Dec3 decodes it to progressive YV12, chroma values will represent an average for lines 1&2, and for lines 3&4, which is correct for progressive material. Fine.

Let's assume progressive material, encoded as interlaced MPEG2. If MPEG2Dec3 decodes it to interlaced YV12, chroma values will represent an average for lines 1&3, and for lines 2&4, which is not really correct for progressive material, but probably does not hurt much, except for red/blue diagonals, maybe.

Let's assume interlaced material, encoded as interlaced MPEG2. If MPEG2Dec3 decodes it to interlaced YV12, chroma values will represent an average for lines 1&3, and for lines 2&4, which is correct for interlaced material. Fine. But if MPEG2Dec3 decodes it to progressive YV12, chroma values will represent an average for lines 1&2, and for lines 3&4, which is definitely wrong for interlaced material, and will result in color shimering.

And now you tell me, it doesn't matter at all how AviSynth stores plain YV12 video, progressively or interlacedly, although the chroma channels may share line 1 only with either line 2 (p) or line 3 (i), and line 4 only with either line 3 (p) or line 2 (i). Where is my fault here?
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Old 16th April 2004, 15:56   #24  |  Link
SeeMoreDigital
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This is great stuff!
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Old 16th April 2004, 23:01   #25  |  Link
LigH
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Suddenly, a flash struck my mind, now I know how it works:

I shall not try to build any relationship between pixels and component planes. I shall see the components (luminance / chrominances) as independent planes: Luminance is a plane at full resolution. Chrominances are planes at half resolution.

If I want them to be filtered as interlaced, I shall apply SeparateFields() - then the luminance plane gets split info fields by alternating lines in its plane, and the chrominance planes get split into fields by alternating lines in their planes.

Anyway, it would be nice to know if the image source filter read the image content from one whole frame, or if it weaved it from two fields; although interlaced color space conversion shall only be applied if the content is combed, but not just always if the source was encoded field-based.

Therefore, please excuse me confusing you - sometimes I even step onto my own slow uptake line...
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