Setting a split point prior to encoding

[Bill_st]

Hi, I'm pretty new to MPEG4 encoding and I've started using GK 0.28.8 about a week ago, with mostly good results :D .

My question is simple, I'm used to MPEG1/2 encoding using DVD2SVCD and even though I'm mostly pleased with the functionality of GK I miss the possibility of setting my split points prior to encoding anything. It seems that the only way to split it now is either trusting your luck with the auto split feature or finding a good KF in a 3-5 MB window which again is a matter of pure luck, especially when you are encoding with high bitrates. My first experience was Raiders of the Lost Ark and even though I reserved 5 MB I couldn't find a single KF where I wouldn't cut a dialogue or something. Is it so detrimental to the quality of the movie to encode it in two separate pieces and split it close to the middle of its duration (assuring a nice disk change) rather than the current process?? :confused: And even so, would it be that difficult to implement? I'm sorry if this has been discussed before, but after searching around I haven't found anything about it.

[musicnyman]

the way i go around this is to set a custom size in auto gk, not divisible by 700 megs. so say you wanted two cds, make the custom size 1401 or 1399. this way it won't split the file and you can do it yourself in virtualdub. might want to make it a little smaller than 1399 so you have room to make sure you can select the right disk change sequence.

[Bill_st]

Yes,I know you can define a smaller disk size to give you a little headroom between disks to find a suitable place to split the file, but still it depends on the particular movie whether there will be a good split point or not this way. At roughly 1650 kbps of video and 384 kbps of audio for a typical 2 disk encode with AC3 soundtrack those few MB that you are taking of each file represent less than 20 seconds of running time, making it extremely likely that you'll end up with encodes that end abruptly in the middle of a dialogue or action sequence. I can think of lots of movies that have sequences that last several minutes where it would be very distracting to swap disks in the middle of, like a car chase, a fight, an important dialogue etc..

I don't know, perhaps I'm spoiled ;), but I suppose I'm not alone in thinking that it is much more convenient to swap disks *exactly* where you want it, maybe 2-3 minutes off the point where the current process would split it, in exchange of perhaps 1-2 % less image quality. And anyway maybe the few MB saved by encoding it in one piece and splitting it later by file size are somewhat offset by the 3-5 MB that you have to shrink each half to avoid splitting it with the autosplit.

[musicnyman]

bill_st, agreed, it would be nice to do this in auto gk, and you would have to leave anywhere from 20-50 megs headroom to find the split point you want and make sure they still fit on a cd. if you really want, use the manual gordion knot and encode the two cds seperately with the split points you want...i know it's more work, but that's what i would do if i "had" to have my exact split points. you could let auto gk do everything up to the encoding process, ie encoding ac3/mp3 audio, creating the avs file, cropping etc... then use virtualdubmod manually to encode the two cds after you have your AVS file ready from auto gk. personally, i would just use gordion knot manually if i had to do that.

[Bill_st]

??? :confused: I think there is a misunderstanding, I was talking about the manual GK all the way, as I stated earlier I'm new to MPG4 frontends, and I haven't got around to installing auto GK yet. So, is there a way to select the split points with the manual GK within the GUI just as the credits start?. I saw the "select credits start" button, and was hoping there would be a similar "select split point" button alongside it, but there wasn't. The guide in this website reflects this, as it only mentions the post-encoding way of handling 2-disk encodes with Nandub.

The way I found so far in GK to encode as 2 different files was saving a .avs file with the desired resizing/cropping options, duplicating it and editing them with notepad to add a trim(**,**) command for each, and then opening them in GK as two different encodes (deselecting resize/crop in the GUI to avoid doing it twice). But then I have to transcode the audio track separately with BeSweet, so it is less than perfect.

[manono]

Hi-

You should probably upgrade your GKnot, since 0.28.8 is pretty old.

Is it so detrimental to the quality of the movie to encode it in two separate pieces and split it close to the middle of its duration

Yes. Often there's a lot of action near the end, and if you guess a split point in advance, the second half of the movie may have much worse quality than the first half. However, if you want to give it a shot, you can split by chapters in DVD Decrypter (uncheck half the chapters and decrypt half the movie, and then uncheck the the other half chapters, recheck the originally unchecked ones, and then decrypt the other half of the movie). Then you would make two 1 CD encodes. When done, run the 2 halves through DRF Analyzer to see if the average quants of each half are anywhere near similar. That'll save you from messing with the audio, as the audio will have already been split also.

You already know how to do it with Trims. I'll do it that way myself sometimes, by redoing the whole thing when I just couldn't find a good place to split. If you want GKnot to do the audio for each half, take a few minutes to split the AC3 using HeadAC3he. It's real easy to do, and takes no time at all. Or, if you plan to use the AC3, enter the AC3 size for each half in GKnot.

What I'll sometimes do is to save a compression test as an AVI, split that in half, and then go back into GKnot, scrolling through the .d2v video, looking for a good split point around where the half size point was in the compression test AVI. If that point is far from the midway point, I'll adjust a bit because the CBR AC3 might skew the results some. Then I'll set Trims to encode the movie in two 1 CD halves. That works pretty well to give equal quality for both halves. Did that make any sense?

[Bill_st]

Absolutely. A very thorough answer, thanks. :D

Originally posted by manono

You should probably upgrade your GKnot, since 0.28.8 is pretty old.



I just went for the "stable" version, if 0.32 is not beta as in "plagued with bugs" then sure, I'll upgrade.

[deleted dumb comment]

Originally posted by manono

What I'll sometimes do is to save a compression test as an AVI, split that in half, and then go back into GKnot, scrolling through the .d2v video, looking for a good split point around where the half size point was in the compression test AVI. (..) Then I'll set Trims to encode the movie in two 1 CD halves

Sounds good as well. If it works it would be an idea to include something like it in GK as an extension of the compression test, don't you think? ;)

[iradic]

hi, i never done any spliting...

but if you do xvid what about setting new zone with "start with keyframe" (this frame you find out - which you want) and that is it...
encode and split file after... keyframe is just where you wanted it...

bye

[ukb007]

Hi.

For 2-CD rips, one can make 2 d2v files at arbitrary split points and encode them separately at one's preferred CD-sizes.

Regards.