Originally Posted by coyoteaz
I don't know where you draw the line of what constitutes a long GOP, but NBC O&Os are currently using up to 2 second long GOPs, and they used to go up to 3. Fox's GOPs aren't always 15 frames; they go up to 30 during black frames, and when they do a hard cut from black to whatever instead of a fade, the content will almost always be within 2 frames of the beginning of the GOP. It's not always right on the start since it can fall on the I frame or either of the 2 preceding B frames depending on where in the pattern things fall. It seems pretty obvious that the encoder is buffering at least 1/2 to 1 second worth of video in order to better make frame type and bitrate distribution decisions.
There aren't any O&Os is my market
I only use Fox as an example as I do not capture any of the other local affiliates. What I have is either H.264 or MPEG-2 (both high bitrate). I won't touch CBS with a 10ft pole, as they are on my sh!tlist, due to their horrible program invading snipes. There are times that NBC wants to be banned as well.
What I have from Fox is edited, so I didn't have any raw material in which to look at everything. But, even if they do go out as far as 30 frames, that is no where near the multiple seconds that is done with H.264.
Comparing x264 to anything else isn't really a fair comparison. x264 is vastly superior to every other H.264 encoder available. What x264 can do in a 2-pass encode would take a hardware encoder at least 50% more bits to do to generate similar quality.
The point is that H.264 at 10 Mbps is not going to be macroblock heaven, even with the single pass encoders. That basically implies that single pass MPEG-2 encoders at 20 Mbps are going to put out crap as well, based on the 2:1 accepted rule. That would also mean that ATSC OTA was doomed from the start, since we are lucky to get 15 Mbps these days.
Unfortunately, when it comes to consumer TV quality, everyone is on the short end of the stick, no matter how long a GOP is. It takes a Blu-ray release of a TV show to see how great the video image can be.