Originally Posted by djoberg
Bit rate and the quality of the transfer are surely two huge factors that affect image quality, but whether you're viewing cable, satellite, or streaming, that won't change (i.e. they will be the same with a title no matter how you are viewing it, unlike the compression factor, which may vary).
That's not true at all. Bit rate varies on pretty much every source. Bit rate for a lot of streaming stuff tends to ride around 6-8Mb/s, while cable and satellite channels tend to ride anywhere from 10-24Mb/s (it rare to see more than that these days with all the frequency packing). Now, obviously, the codec plays a role in whether the lower bit rates do visible harm or not. MPEG2 will degrade very quickly, while MPEG4 might take longer to see real harm. That doesn't even take into account things like AVC, VC1, Flash, Silverlight and others that can all affect media differently due to bit rate, motion in the content, the total resolution and even the aspect ratio of the content.
The problem with low bit rates on streaming media, which often uses some form of MPEG4, is that the results aren't always visible on smaller devices. It's not until you watch those things on your living room TV that softness and overall loss of detail start becoming very apparent.
Finally, the bit rate is a fundamental part of compression. Reducing the bit rate is one of the major things that is done in order to compress something. In other words, you reduce the color bit depth, the DPI, the horizontal or vertical resolution and the audio quality of a video file in order to reduce the bit rate - which makes for a smaller file requiring less transfer overhead and storage space. Finally, the codec you eventually export a file to plays a part in what bit rate you need to avoid compression related issues.
When I was sampling Crackle yesterday I watched The Fifth Element for a couple of scenes. Being very familiar with this title I was able to compare it with both satellite and Blu-ray and it was a notch or two BELOW what I've seen on Dish broadcasts. Granted, Crackle is a free channel with only 720p, but I was expecting more knowing the quality of the transfer.
The Fifth Element is actually a big test for compression, since compression can negatively affect the ability to reproduce some of the movie's fast action scenes without blocking. Also, the film's wide color palate quickly muddies when video frequencies are dropped to reduce playback and streaming requirements. Honestly, until the day comes that you can stream a movie at the best BD quality, I wouldn't try to watch it any other way. There's a reason this movie has been a brute strength test of any video format or home theater equipment for many years. It makes every step of the process work really hard to make it look and sound good.
...and yes, there's a reason the movie was re-issued. It sucked big time in its first BD release.
BTW, over in the Blu-ray PQ Thread we've had an ongoing debate (for several years) over bit rates. Generally speaking, the higher the bit rate the better the image, but not always. I've seen Blu-ray titles with bit rates in the upper teens and lower twenties that had excellent PQ, with stunning details, depth, and clarity. Conversely, I've seen a few titles with bit rates that were consistently in the thirties that didn't fare so well. So, one can't always go by bit rates. There are surely other factors such as post processing that can be detrimental to a transfer, but when I made my remarks in my post yesterday I was especially thinking of The Fifth Element, which is a very good transfer (the Remastered Version, that is) and I was disappointed with what I saw. Now that I think about it, perhaps it was the old transfer (and not the Remastered Version) that Crackle was offering.
That's precisely why you can't rely on any one factor to determine picture quality.
One factor is content: A low bit rate static shot of a mountain on a clear day can look as good as the same shot at a high bit rate - until the clouds roll in, the camera pans, or some inconvenient bird flies through the frame. Further, the aspect ratio can affect quality at the same bit rate. More black either from a scope feature or from a 4x3 picture will compress better than something that is 16x9 and uses the full frame for moving video. Black and white can compress better than color. Dull colors compress better than bright ones. Pictures with less contrast (no true blacks or whites) will compress better than those that range from inky blacks to blazing whites.
Another factor is the codec: MPEG2 is very lossy. It doesn't take much to make a mess of an image with it. On the other hand, MPEG4 is very tolerant to compression, but will still show softening and eventually blocking if the bit rate for a particular type of content drops too low.
Resolution: You can play a lot of tricks with resolution. For example, while a DVD is still only 480 lines, you can "upconvert it" and it will look noticeably better on an HD set. However, it's a trick and not real resolution. It's no comparison for the same content in HD, which, due to many factors is usually no comparison for Blu-ray, which is no comparison for the digital master used to create all three. Early HD stations also tended to use HD tape formats that weren't full resolution HD. They actually topped out at 1440x1080i. HBO, HDNet and others used these formats. Both Dish Network and DirecTV used this method to reduce the bandwidth they needed to send out HD some years back (which came to be known as "HD Lite" - something that was done to reduce the affects of lowering the bit rate to fit more channels per transponder in MPEG2). The biggest case of resolution not being what it seems is with Turner Classic Movies, which has yet to show anything in HD in the US. It's all upconverted at some point in the chain.
There are other factors that can affect the transfer, like the number of audio channels (more channels can equal less room for video when space is tight) and rate shaping tools that some MSOs employ on their video offerings and ISPs can use on internet traffic. Even the quality of the video chip in the playback device you use can affect the image. For example, something containing a chip from Faroudja will process video better than some of the cheaper offerings from bargain basement equipment.
At any rate, I do need to think about the points you made, especially the point about "reducing the horizontal resolution," which I had never heard of.
Explained above...Edited by NetworkTV - 8/17/12 at 7:28pm