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Old 12th December 2005, 20:07   #11  |  Link
cedocida
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Join Date: Mar 2002
Posts: 38
Quote:
DV compressed video does not distinguish between interlaced or progessive. DV-input and DV-output allways is considered as fields. It only has a mechanism to efficiently compress video which is progressive, i.e. if both fields are from the same time instance.
I have to correct myself.
Probably you know this all, but because often I read something about progressive- / interlaced-DV and how to deal with this material, I think there is a little bit confusion.

Unlike MPEG-2 which has several modes for interlaced and progressive video, different DCT-types for fields, frames, interlaced frames and different color sampling positions, for DV the following applies (to the best of my knowledge):

* DV-Video compresses a complete Frame (720x576 PAL, 720x480 NTSC)
color, aspect ratio etc. is based on analog video signal, digitized according to ITU-R REC.BT.601
* there is a flag in the header indicating that the encoded video is supposed to be interlaced or progressive, and a flag specifying the field order (tff/bff), but
* there is no special interlaced or progessive mode as in MPEG-2. The position of the color samples are allways the same and the macroblock and block areas are defined on the full frame. The only way to improve compression for interlaced or progressive material is to apply either the "normal" DCT or the 2-4-8-DCT (AFAIK only used in DV-compression) on the blocks (8x8 samples of one component). Every single block has a flag indicating the DCT type. So, even if the source material is progressive, for some blocks, compression could be better when choosing the 2-4-8-DCT and for interlaced vice versa.

To answer your question,
Quote:
Does it refer to field based or frame based IDCT?
In DV, we don't have a field based DCT/IDCT except this special 2-4-8-DCT which can be individually used for each block. All Macroblocks and Blocks are defined on the full frame.

@Wilbert
Quote:
Why is it that in (4) the chroma positions are not relevant? It seems to me you should know how to apply the weighting during upsampling. To apply the correct weighting you should know how the YV12 clip is sampled, thus you should know whether you are dealing with case 1, 2 or 3. Please clarify
I allways assume, that the compressed DV material, which maybe was created by Cedocida or some other codec or camera, is compliant to the DV standard. So there is no big uncertainty how to correctly upsample it to YUY2 or RGB.

@neuron2
Your welcome to add my little explanations to the Readme. Thx again for sharing the files.
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