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Old 4th February 2025, 07:44   #101  |  Link
rwill
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Originally Posted by kurkosdr View Post
If memory serves me well, a "field-picture" encodes a pair of interlaced fields (top and bottom field). Basically, in MPEG-2, in interlaced mode, you can either have a picture encoded as a progressive frame or as a pair of fields. The first type of picture is useful for "fake interlace" (needed to get a 25p video on DVD-Video because DVD-Video doesn't support progressive mode for example) or for scenes with zero motion in true interlaced video, and the other is for scenes with motion in true interlaced video.

Note: when I say "true interlaced video" I mean the kind of interlaced video that would give you those annoying comb artifacts during motion if you tried to weave/overlay its field-pairs into frames.

If so, does it mean y262 can't encode true interlaced video?
You have not understood interlaced support in Mpeg-2.
y262 can encode interlaced content just fine.
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Old 4th February 2025, 11:46   #102  |  Link
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You have not understood interlaced support in Mpeg-2.
y262 can encode interlaced content just fine.
Then what are "field pictures"? Any hint?
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Old 4th February 2025, 17:12   #103  |  Link
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Then what are "field pictures"? Any hint?
Well maybe I am the wrong one to answer that. As far as I know a field picture in the context of Mpeg-2 is a coded picture where picture_structure is equal to "Top field" or "Bottom field".

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Old 4th February 2025, 17:16   #104  |  Link
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This thread should be integrated into this thread: https://forum.doom9.org/showthread.php?t=185662
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Old 4th February 2025, 17:29   #105  |  Link
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Originally Posted by rwill View Post
Well maybe I am the wrong one to answer that. As far as I know a field picture in the context of Mpeg-2 is a coded picture where picture_structure is equal to "Top field" or "Bottom field".

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That's what the internet tells me, a "field picture" is basically a field. If you have a 720x576i50 video, a field picture will be a 720x288 picture to encode a field (either top or bottom). Because if you have motion in that particulate field-pair and try to weave the two fields into a 720x576 frame and encode it as a "frame picture", you'll get combing artifacts that will need lots of bitrate to compress without massive artifacting. So, better encode that field-pair it as two pictures 720x288 each in "field picture" mode, not "frame mode".

Anyway, have you tried true interlaced (with combing artifacts when you weave/overlay) with y262? How well does it perform, say at 4mbps for 720x576 during motion scenes?

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Old 4th February 2025, 18:25   #106  |  Link
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Anyway, have you tried true interlaced (with combing artifacts when you weave/overlay) with y262? How well does it perform, say at 4mbps for 720x576 during motion scenes?
Well of course I have. It performs. I do not know how well because I had skipped the stuff with the reference.
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Old 5th February 2025, 03:59   #107  |  Link
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Anyway, have you tried true interlaced (with combing artifacts when you weave/overlay) with y262?
I would not call that 'true interlaced'. I would call that treating interlaced video as progressive. It is never good. If a codec cannot encode as fields it is better to bob deinterlace than encode the two fields from different timepoints in the same frame.
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Old 5th February 2025, 07:51   #108  |  Link
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I would call that treating interlaced video as progressive.
What kurkosdr described, with is own words, appears to be interlaced content. I do not know why you suddenly come along with treating it as progressive content. No one talked about that. Can you explain further?
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Old Yesterday, 22:42   #109  |  Link
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I mean encoding an interlaced frame as a single picture with combing artifacts (treating it as a single progressive frame) results in much worse quality than encoding the two fields as seperate pictures and weaving during decode.

The combing artifacts are very sharp high frequency detail that does not work well with our lossy frequency domain compression methods. This is even worse when considering 4:2:0 chroma sampling.
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