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Reply #164: Did you see this article from Muckraker? [View All]

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Flatulo Donating Member (1000+ posts) Send PM | Profile | Ignore Tue Nov-25-08 07:26 PM
Response to Reply #79
164. Did you see this article from Muckraker?


While reading some of the coverage and investigation done by Maher Osseiran on the bin Laden confession tape, and his assertion that the tape is likely actually a tape of bin Laden himself, it occurred to me that since the tape was recorded in the Pakistan region, it was likely recorded in PAL video format. In the United States, we use the NTSC format. The difference is primarily that the standard PAL format has the same spatial resolution horizontally, but vertically it has a higher spatial resolution (720 x 576 for PAL 720 x 480 for NTSC) than doe NTSC. Many PAL and NTSC converters simply eliminate the extra horizontal lines from the PAL format in order to conform to the NTSC format. This results in an image that appears to be squashed along the vertical axismaking people and objects look fatter after the conversion.

Using video provided to him by Maher Osseiran, Tremblay suspects that a linear interpolation PAL to NTSC conversion method was used in this instance. This method basically eliminates every fifth scan line from the PAL video, thus matching it to the number of scan lines for the NTSC video standard (480 lines for NTSC versus 576 for PAL). Besides linear interpolation, there are other conversion methods and software that might have been employed to accomplish the same distorted effect on the original video. Tremblay is basing this conclusion on the following probabilities:

a. The video was made in Afghanistan or Pakistan and therefore was likely shot in PAL standard format

b. The video that was delivered to him is now in NTSC digital format, so at some point it was likely
converted from PAL to an NTSC

c. If one assumes that linear interpolation was used to sample down the PAL image to fit the NTSC format,
and since scaling the vertical dimension of the video appropriately reestablishes the known proportions of
the people who are purported to appear in the video, then he personally finds that sufficient confirmation
that this process (or a similar process) was indeed applied to the original video causing it to be out of
proportion in the vertical dimension.

There's some other good stuff in there not related to vertical compression.

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