I've been told that the hits bits are just passed on, and that the customer base and the proposition -- is that you only need to decide which programs to pass on, and no need for processing. The people that I know that use Pathfire also just pass on the bits. By the way, I don't Pathfire can offer HD programming. Yet. John Willkie -----Original Message----- >From: Craig Birkmaier <craig@xxxxxxxxx> >Sent: Jun 19, 2008 3:41 AM >To: opendtv@xxxxxxxxxxxxx >Subject: [opendtv] Re: Video compression artifacts and MPEG noise reduction > >At 10:51 PM -0700 6/18/08, John Willkie wrote: >>yeah, the box, fool, is practically useless for that, since, uh, >>NOBODY takes a compressed MPEG-2 stream back to baseband, then uses >>this filter, then recompresses it. >> >>And a "prefilter" would imply that it goes before any compression, >>not in the middle of a decompression/compression daisy chain. Kind >>of hard at the beginning of a chain to know the noise that would be >>encountered in the middle of the chain. >> >>Indeed, taking a compressed MPEG-2 stream down to baseband would >>actually impose noise JUST BY ITSELF since MPEG-2 compression is >>lossy and asymmetrical. So, you'd be lucky if the "prefilter" was >>able to remove the noise caused by the decompression to baseband. >> >>The market for this device, Bert, is most likely YOU. Let us know >>how you fare with it. >> > >Actually John, there are many situations in which a broadcaster or >cable head end might be trying to clean up a compressed feed then >re-encoding it for emission. > >Many cable systems utilize the HITS (Headend In The Sky) service. > >http://www.hits.com/ > >This service (I believe it is operated by Comcast) compresses a wide >range of cable networks and distributes them to cable head ends via >satellite. > >In most cases these feeds are not decompressed, however they may be >groomed by devices like the Cherry Picker to cram more stuff into a >cable multiplex. > >Because of the high cost of satellite bandwidth, many syndicated >programs are now distributed to broadcast facilities via satellite as >compressed MPEG-2 bitstreams. And then there is the age old practice >of capturing the broadcast signals from other stations in a market to >source clips for use in newscasts (with permission of course!). So it >is becoming far more common for the feeds coming into a station to >arrive as compressed MPEG-2 bitstreams. > >The MNR mode of the Algolith device is specifically designed to deal >with quantization noise, also know as mosquito noise. This type of >distortion is much more predictable than the random/Gaussian noise >found in uncompressed sources. It typically occurs at the boundaries >of high frequency details, so a clever algorithm can look for these >details then process the distortions around them. > >You are correct that MPEG-2 creates "noise," but the noise is >correlated to image detail, not random, and thus may be reversed to >some extent if the damage is not too severe. > >And yes there may be a consumer market for devices that undo the >damage of video compression. Some of this was incorporated into h.264 >decoders (the deblocking filter tools). And h.264 dropped the 8 x 8 >DCT quantizer entirel, replacing it with a scalar quantized that is >less complex and more accurate: > > >http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/76/27384/01218192.pdf?temp=x > >Summary: This paper presents an overview of the transform and >quantization designs in H.264. Unlike the popular 8/spl times/8 >discrete cosine transform used in previous standards, the 4/spl >times/4 transforms in H.264 can be computed exactly in integer >arithmetic, thus avoiding inverse transform mismatch problems. The >new transforms can also be computed without multiplications, just >additions and shifts, in 16-bit arithmetic, thus minimizing >computational complexity, especially for low-end processors. By using >short tables, the new quantization formulas use multiplications but >avoid divisions > >So h.264 provides a significant improvement in arithmetic accuracy >and the visibility of artifacts is reduced by acting upon smaller 4 x >4 regions of the image. > >So my educated guess is that products like the Algolith device will >not find their way into TV receivers. The shift to improved >compression techniques will make this unnecessary. And we can hope >that broadcasters and other program distributors have learned that >excessive compression is > >BAD! > >Regards >Craig > > >---------------------------------------------------------------------- >You can UNSUBSCRIBE from the OpenDTV list in two ways: > >- Using the UNSUBSCRIBE command in your user configuration settings at >FreeLists.org > >- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word >unsubscribe in the subject line. > ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.