DV Pix - Multigeneration stress tests with different codecs
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Text: The DV Format

[updated 17 January 2000]

Here are the full, 72x480 stress test images from several codec settings as presented at the Digital Video Café, January 2000. DV Plus clamped (normal) and full-range mappings were tested along with Apple DV - NTSC at Best and Medium settings. The test is more fully described here.

The original image was built in PhotoShop on the PC and compressed with DVSoft into a DV AVI to get it into the Y,Cr,Cb color space, so that the brightness scale or contrast of the image would remain the same despite different RGB-YCrCb mappings in the different codecs. The AVI was brought onto a Mac using Thursby Systems' DAVE cross-platform networking software (highly recommended!) and read into Final Cut pro, where repeated renderings were done by supering the generation info and exporting to a new movie. That movie was then read in, a super was done again, and the cycle was repeated as many times as necessary. Thus the generations listed are for the codec under test, but there is one generation of DVSoft compression preceding the test compressions.

The Apple DV - NTSC codec is version 2.1.2, supplied with Final Cut Pro 1.2 and expected to be part of the QuickTime 4.1 general release.

DV Plus is the DVSoft-derived codec offered by ProMax in the DV Toolkit 3.0 release. It offers three modes of operation: clampled luma / chroma, full luma / clamped chroma, and full-range luma /chroma. Clamped is the "normal" mapping used by most DV codecs (and expected by most NLEs wherein the 16-235 nominal brightness range of 601-format digital video is mapped to 0-255 in the RGB color space. Unfortunately this leads to white clipping, so the full-range modes map 0-255 to 0-255 in either luma alone or luma and chroma both.

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Original, uncompressed graphic
Original, uncompressed image
1st GENERATION: DV Plus, clamped luma / chroma
1st Generation DV Plus, clamped
1st GENERATION: DV Plus, full-range luma / chroma
1st Generation, DV Plus, full-range
1st GENERATION: Apple DV - NTSC, Best quality1st generation, Apple DV - NTSC Best
1st GENERATION: Apple DV - NTSC, Medium quality1st generation, Apple DV - NTSC Medium
5th GENERATION: DV Plus, clamped luma / chroma5th generation, DV Plus, clamped
5th GENERATION: DV Plus, full-range luma / chroma
5th generation, DV Plus full-range
5th GENERATION: Apple DV - NTSC, Best quality
5th Generation, Apple DV - NTSC Best
5th GENERATION: Apple DV - NTSC, Medium quality
5th Generation, Apple DV - NTSC Medium

Other Pix

Enlarged details of the credit card graphic used on this test, compressed though these and other codecs, are shown on the pix-codecs main page.
 
 

Copyright (c) 2000 by Adam J. Wilt.
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Last updated 17 January 2000.