Automating Virtual Dub - 2 pass

[ptaylor]

I've been using AutoGK for a few months now, and man does it do a great job... I have 30 minute episodes of some kids shows that I've encoded to about 150 MB and they look very good... Very sharp picture, with no artifacts... On the TV it looks almost as good as the original 1 GB MPEG file. It's auto-resizing it to 352x272 from the 720x480 I believe, but you don't really notice the loss of detail. AutoGK takes all the guesswork out of it and you just end up with highly compressed, good looking video. But, of course, I can't command-line it... I have spent a little time trying to use the AutoIt program that I mentioned... Mouse movement doesn't seem to want to work really well with AutoGK, so I'm looking at command-line alternatives....

Now, I've tried encoding with xvid with both mencode and virtualdub in the one-pass mode with a bit rate of about 700. In each case, I ended up with a file that is about 170-180 MB in size (close to what I get in AutoGK), but the quality is WAAAYYYY off of what I get out of AutoGK at a smaller file size... A *LOT* of artifacts, jumpiness, etc... This may be due to the resize, at least partially... (I used the resize to 640x480 with mencode, but it didn't turn out to look as good as the virtualdub 1-pass encode)

Now, I have tried to get a good 2-pass config going for VirtualDub, but so far I'm failing badly. I am looking for the highest quality for the smallest disk space footprint so that I can use it in my automated program that I'm writing...

Does anyone have any good virtual dub profiles to perform 2-pass compression? Something in the 300-350MB per hour range would get me just where I want to be.

If anyone is a whiz with VirtualDub, please post your configs... I should be able to post my app within a few days, assuming I can get a cmd-line encoder working at a decent compression rate.

Paul

[ToxMox]

I hate to link to another forum but it seems someone at the snapstream forums has created an AutoIT script for AutoGK that seems to work pretty well:
http://forums.snapstream.com/vb/show...56&postcount=1

[ptaylor]

Thanks - I have actually been working a bit on getting an AutoIt script to work with AutoGK, but haven't had any luck...

The instructions for the script say to pass it a filesize or percentage along with a source MPEG file and a destination filename...

The problem I have with his script is that I can't easily integrate it into my application... I want to either have a cmd-line encoder that I can control and run start-to-finish, or AutoGK, where I can queue up all the files, keep a record of which ones were started compressing, then check the status of them the next run to see which ones are done.

With the script in it's current state, I can kick off a single compression job, and AutoGK doesn't close when it is complete. Note that I said a single job - that's not a batch of files to be compressed, but rather one single file...

The BTV program that he includes appears to watch a source directory looking for new shows to recompress... It looks like the shows have to be named a very specific way... I might be able to use this program to somehow do the "dirty work" for me, assuming that it will add multiple files in a batch, or sense when a job is done and start another one off, or something of that nature, but I'd rather have full control instead of trying to hack my way around...

I've sent him a PM asking if I could have the AutoIt source so I could see how he managed to do it. If so, I'm almost certain that I could use his methodology within my program...

Paul

[ptaylor]

Well, I found out that he didn't put a passphrase on it, so I was able to convert it back to script... So, I'll be working on this over the next few days or so and see if I can integrate it... Looks like a LOT more stuff than I thought it would be, though...

Paul

[nielm]

Ptaylor: if you are comparing a vdub encode that resizes to 352x272, and an mencoder encode that resizes to 640x480, but using the same bitrate, then you are comparing apples to oranges! The mencoder encode will be a lot worse simply because there are a lot more pixels to encode to the same number of bits
150Mb for 30min of 352x272 = 0.24 bits/pixel
170Mb for 30min of 640*480 = 0.08bits/pixel
-- at that rate, it is no wonder the mencode is horrible!

Doom9 recommend about 0.25 bits/pixel, and nothing below 0.17 bits/pixel...

Also, you will need to specify a deinterlacing filter in mencode (kerndeint is a good one -- encoding interlaced is a bad idea and looks horrible!), and possibly some post-processing filters to remove noise before encoding...

Check out the other mencoder thread

[ptaylor]

Well, I guess my main point was that AutoGK does all that stuff automatically... I'm not a whiz when it comes to encoding...

At this point, I'm planning to try to move forward with AutoGK, but I'll give Mencoder a chance in a few minutes to see if it can impress me... I used your settings in the other thread for my test...

[ptaylor]

I did have another issue with the mencoder encoded test file... Sage didn't display the bar properly, showing the progress through the file... Hit FF once, and it was over, even though it's a 30 minute show. I'm running another mencoder test file now, should be done in about 20 minutes.

Another test file that I encoded with AutoGK last night turned out to be at 368x288.

Wouldn't it be best to let AutoGK decide how to scale it, etc. since it does everything adaptively, based on the content of the video file?

I might be able to read the created timestamp and the modified timestamps to determine if it's a 30 minutes show, an hour, etc. and allow the user to have a size you can set in AutoGK for common show times (such as 150 MB for 30 minute shows, 300 MB for hour long shows, etc)... Or just set it for a certain percentage no matter the length of the show and let 'er rip...

Anyhow, I'm leaning strongly toward AutoGK right now... I know it is slower than other methods, but the results (that I've created with it) have looked the best... We'll see..

Paul

[nielm]

Sage didn't display the bar properly, showing the progress through the file... Hit FF once, and it was over

That may have been the zero-length file issue, where Sage cannot read the length of the file when it adds it to the library because the file was in use at the time.. (detailed info should show 0 mins). Workaround is to rename the file and rescan.

[ptaylor]

This time I didn't see that problem (with the file that I just created)..

The AutoGK file looked better, quality-wise... There was some definite artifacting in the Mencoder file. It was most noticable just after screen transitions around the faces of the actors.

I'm going to try to get something automated with AutoGK for now...