Robshot method - I don't understand the grey areas

I've used the search feature, read the guide multiple times but am still struggling with the grey areas thing. I feel dense :( Looking at that little picture in the guide I don't get where the "gray backround" is. Same deal when I use a vaf with a very low avg bitrate. A pre-school level clarification would be greatly appreciated :D Thanks :)

I agree 

Matthew, I'm with you on this point. I have done a couple of movies to date using CCE, and been generally pleased with the results. However, I know I'm missing out on some of the "finer points", and going into Advanced, using the multi pass VBR, then checking the "grey areas" does leave me hanging in the air as well. Is there anybody out there who can "talk us through" And one other small point, what are those purple vertical lines ?? (I know what the orange ones are) HomerJ :confused:

purple lines where? I don't see any. But that also means that you can follow the method without knowing about every color on screen ;) I'm sure the CCE manual will hold the answer if you really need to know it. @HomerJ: If you can be more specific as where to get stuck you may get some help..

From the CCE Manual: Quantization scale display The quantization scale is displayed in the graph shown in Fig. 3.16. To display the quantization scale, select Q.scale at the right of the graph. Just like the case of the bitrate display, each white line, green line, and red line of the graph indicate the quantization scale of I picture, P picture, and B picture, respectively. And yellow line indicates the average quantization scale of GOP. The double vertical lines at the center show the currently selected timecode. As the value of the graph becomes smaller, the distortion of the frame becomes smaller. When the quantization scale is displayed, the background is colored with green, gray and red. The part where the background is green is encoded at relatively good image quality, the gray part at standard image quality, and the red part at image quality where distortion tends to be outstanding. Once one becomes used to reading this display, image quality can be roughly estimated before encoding. Use this graph for setting the bitrate. *********** Also, I don't think anyone knows what those purple lines are. I see them and they are in the CCE manual on Advanced VBR settings, yet they don't talk about them. I just assumed that they were where the bitrate was maxxed out, but I never really examined it too closely. There was one other post on the matter in the CCE forum but no one really responded except to say "I think you mean the orange lines." -Cole

Make sure you select Q.Scale first. If your movie is simple movie such a comedy, you might not have the gray background on the graph, if you do it probably won't be a lot in the film. So if you don't see any gray, that means you're already done. Gray areas appear on the graph for several reasons. If the scene is complicated to interpret, such as the water scenes in Saving Private Ryan, the area will show gray and you might see distortion in the preview window. The purpose of the guide is to dedicate a higher bitrate for that scene, for example a movie with an average bitrate of 3500 might have 4-5000 bitrate on a complex scene, you can up this average by raising the min bitrate higher from 5500 to 9000, this will usually improve the image quality and the gray will disappear but this will add to the size. Some scenes are so complex that increasing the bitrate to max will not help at all. If you transcode a long action movie with a low bitrate, you should find tons of these gray background. Increase the bitrate average and you'll notice that the number of "grays" drop significantly.

Thanks for the feedback guys, I've been real busy this past week, and had very little time to spare to look at this "issue". But IT'S THE WEEKEND !!!! So off to get a "new challenge", and spend a bit of what I call "quality time" to look into this part of CCE. I'll report back in a day or so. HomerJ :)

I think the lines referred by Matthew above are the "scene change" lines... CCE recognizes scene changes and (I believe) starts an I frame sequence when it sees one...