Bandwidth, Compression and HD Picture Quality

hoopnoop · Post by **hoopnoop** » Tue Feb 15, 2005 9:10 am

I recently added Cable HD (Adelphia with a Motorola 6412 STB) and compared it side by side to what I had from Voom and found out to my surprise that the HD picture quality was superior on a number of the same channels via cable. This was especially noticeable for Discovery HD and the premium channels in HD. The difference was quite noticeable as the Voom channels were much softer while the cable channels were much sharper and crisper. I think it is because Voom tries to cram too many HD channels into its existing amount of bandwidth.

My question is, where is the best place to go for a tutorial that will allow me to understand how it is that things like bandwidth, compression, bitrate, etc. effect picture quality? I know that Richard mentioned something about k-band at one point -- what is that? Also, is there a source to go to in order to find out how much bandwidth your local cable or satellite provider is allocating towards its HD channels? It seems that everyone thinking about switching providers is faced with a big uncertainty -- how good will the pq be if I switch? Yet, we often have little information to go on in making a switch. Wouldn't it be useful if the cable and satellite providers were forced to release information relating to picture quality issues like this?

Any thoughts or insights on this subject would be appreciated.

akirby · Post by **akirby** » Tue Feb 15, 2005 11:06 am

Question: were you using the same input when doing the comparison? If the inputs were different then that could make a difference. If possible either use the same input or switch them and see if you see the same results on different inputs. Or better yet get them all calibrated.

hoopnoop · Post by **hoopnoop** » Tue Feb 15, 2005 1:53 pm

It was the same input. I have only done a basic calibration using Avia and also some other tweaking as recommended by other Sony GWIII users.

Richard · Post by **Richard** » Tue Feb 15, 2005 2:23 pm

It seems that everyone thinking about switching providers is faced with a big uncertainty -- how good will the pq be if I switch? Yet, we often have little information to go on in making a switch.

I don't think that is going to change either.

I just had a discussion on the TIPS List about poor VOOM picture quality and nearly everybody thought I was off my rocker. The problem is that for the most part we are all seeing the same things and the difference is how many of us really know what it should look like. Many simply accept the artifacts as a natural part of the image.

Unfortunately there is no good site I know of that takes real images and shows you how they are messed up. While this has been considered for HD Library it would be very time consuming and difficult to document and is why it has not been done yet.

If you check the bit shaving thread there are some sites that are starting to keep a record of the bit stream rates.
viewtopic.php?t=4175

And while your comments revolve around the image others are also noting degraded audio performance.
viewtopic.php?t=4474

hoopnoop · Post by **hoopnoop** » Wed Feb 16, 2005 7:20 am

Thanks for the link to the bitrate sites Richard!

Do we have a thread in this forum discussing bandwitdth and bit rates and the like? I think I need a lesson.

Richard · Post by **Richard** » Sun Feb 27, 2005 10:42 am

We do now... Plus a bunch of other related stuff. Many new entries in the dictionaries.

Compression

Bit Stream

hoopnoop · Post by **hoopnoop** » Tue Mar 01, 2005 7:35 am

Thanks for the info Richard! Very interesting and helpful stuff!

I also have a link that I will track down as well...