OK. Another example for the same question. I would like to set the bitrate on an old film that runs 2.05 hours and has a 608x256 (2.38:1) [=19:8] aspect ratio. I already converted it from avi to mpeg2, and the size I got it's 6.8GB, which I would have to put through DVDShrink to fit it into one disk. What bitrate should I use? Even if I have the bitrate calculator, I don't quite see how to use it.
I'm not sure what bitrate calculator you're using, but here's the basics using the one at videohelp (http://www.videohelp.com/calc.htm). Enter the running time for the movie and then the bitrate of the audio. I use PowerDVD (right click on movie while it's playing and select Show Information) to find out the audio bitrate if I'm not sure. Generally speaking you'll have either 192kbps or 224kbps for 2 channels or 384kbps/448kbps for 5.1 channel. Use the numbers it gives you for Calculated Bitrate and DVD Max Bitrate to set the Average and Maximum in your encoder.
Ok. I got it. My bitrate seems to be 4632 kbs. What I wonder is what happens to other data for this film, which might help for a better compression. Particularly the black spaces above and below the film screen, as it is cinemascope. Shouldn't that data be loaded on the encoder too?
If you're wasing bitrate encoding black boxes, it's better to crop them off, and frameserve to the encoder, and let IT worry about aspect. This gives you full bitrate for the actual frame, not the letterboxing on an avi.
[bold] If you're wasting bitrate encoding black boxes, it's better to crop them off, and frameserve to the encoder, and let IT worry about aspect. [/bold] But that is exactly my problem! How to correlate the cropping or frameserving for the encoder, which is not really that straightforward. Except if I am losing something in this explanation. [bold] This gives you full bitrate for the actual frame, not the letterboxing on an AVI.[/bold] What gives me that full bitrate? My remarks probably sound pretty obvious to you, but believe I am being sincere. Please forgive my blindness if it's supposed to be obvious. It seems that I am quite about to grasp it, but it still isn't under my control.
Although black letterboxes don't use much bitrate, in some cases they can make or break the quality of an encode, especially if there's any snow, or fuzzy edges. If you crop them off in something like virtualdub, then frameserve to the encoder, letting the encoder add them where necessary, they're NOT included in the used bitrate. The calculator still applies, because the running time doesn't change, but more bitrate is applied to the actual video, not the letterboxes. eg. Avi with black letterboxes, and some fuzz. Frame size is 352x240 uncropped. Video is widescreen, making the actual frame size 352x190. The encoder is wasting bitrate, encoding 352x50 pixels of black. 25 at the top, and 25 at the bottom. If that number is 12% of the total frame size, you're wasting 12% of the actual video quality. Crop the letterboxes off in virtualdub (or avisynth if you're so inclined), then frameserve (so you don't have to save another intermediate avi, and reduce quality even more), the encoder will use 100% of the chosen bitrate on the actual video, and not encode black boxes. It will, with the right settings, put the black boxes back into the encoded mpg (so the picture isn't stretched vertically), but it uses virtually no bitrate to do it, far less than the original, unless the original is 100% black (not even the slightest bit of grey) and has perfect edges. Any imperfection in the original's letterboxing results in wasted bitrate. The frameserved avi will now be only 352x190, and you need to set the encoder to letterbox it properly, to view on the TV (4:3 aspect). This is one of the main reasons I use only Mainconcept, or Tmpgenc plus (yes, I know it's slow) for encoding these types of avi's. I use Canopus Procoder for all my DV-AVI stuff, because I created the source, so I know what the end product should look like. Clear as mud?
OK. Thanks for your recommendations. Sorry I can only comment now on them. Cropping captured images has always been easy and I did it on all the captures I did from my VHS/S-VHS tapes. Sometimes I also do some cropping on sattelite captures, particularly when the original is 16:9 or anamorphic to eliminate the channel logo. This I do on Procoder, but I don't know how to use it on VirtualDub, because the image already seems cropped when it's a 1.85 or anamorphic movie. Cropping downloaded films is still a mystery to me, as when I try to crop on such films, using the Procoder's video setup, I end up entering the film frame. What do you mean by doing a "frameserve"? How do you do it?
Frameserving is the process of using one program (virtualdub for example) to edit a video, cut commercials, add filters, change sizes, crop, etc., then send it directly to the encoder, WITHOUT saving another avi inbetween.
That sounds interesting. You mean you change some things in the avi file and do not need to save it? How does a program like VirtualDub achieve that? One thing I could do with VirtualDub (BTW I don't know which is better to use: VirtualDub or VirtualDubMod) was separate one audio stream on two AVI files and save them separately as wav files. That allowed me to use the English audio stream instead of the default one on the file I had, that was Spanish. Then I added subtitles and voilá: a rare film I could see again! It worked fine on one of the films, but it did not on the other. The problem seems to be related with the Xvid plug-ins used on this file that do not seem to provide a standard avi file for Procoder to read from. BTW: only Procoder 2 could read and convert the video file, using the wav track for the audio. The other file still resists. So I wonder if there's something else I could do on VirtualDub/Mod that would "standardize" the file a bit more, if you know what I mean. I tried doing an avi file from it with Virtual, but it resulted in a gigantic file that topped my HD. Something greater than 50GB. Something was wrong, no doubt.
