Automatic MPEG to DIVX convertor plugin

[erik]

This is my first plugin

It does about the same as the Auto-Nightly Pocket_DivX .mpg to .avi conversion as made by American_rob but it does not require the installation of additional software and it starts from postprocessing.bat
It automatically converts the recordings from MPEG to DIVX (avi)
You can download it from here mencoder_0_0_0.zip, no additional software is required.
Unpack the zipfile in the GBPVR home directory.
Please be aware that the zip file contains a postprocessing.bat file that will overwrite your current postprocessing.bat file (if any)
Inside you will also find man_page.html containing the documentation for the settings of mencoder, rather complex!!.
The menconder.exe and xvidcore.dll are copies coming from the windows version of mplayer coming from http://www.mplayerhq.hu
Conversion speed of the included settings is 2 times faster then realtime on a 1.8GHz laptop.
Can someone test it?

[reboot]

It works flawlessly.
Mencoder does chew up CPU cycles, and the quality basically sucks, but it does archive to avi as it should.
I would recommend adjusting the video bitrate up (probably quite a bit), which will generate a larger avi, but the blockiness will be less noticable.
I did a test at it's default 1400, then another at 4000, and again at 6000.
I think that about 4500 would be a decent compromise between filesize, and video quality.

[erik]

I tested some settings, for a small file size and reasonable quality it seems better to downscale the vertical and horizontal resolution

so, instead of
mencoder.exe "%~dpn1.MPG" -oac mp3lame -lameopts mode=2:cbr:br=128 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1400 -ffourcc DIVX -o "%~dpn1.avi"

you better use

mencoder.exe "%~dpn1.MPG" -oac mp3lame -lameopts mode=2:cbr:br=128 -vf scale=512:384,eq2=1.0:1.0:0.03:1.0 -sws 2 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1400 -ffourcc DIVX -o "%~dpn1.small.avi"

where 512:384 is the new horizontal:vertical resolution
To get even smaller files you may go to 360:288 and reduce the bitrate to below 1000

[reboot]

Why such strange aspects?
If you're going to downsize, at least stick with proper NTSC/PAL aspect ratios, either half D1, or even 1/4 D1.
These would be (NTSC/PAL), 352x480/576 or 352x240/288.
They could then be re-encoded if necessary, to mpeg-2, without resizing yet again, and the aspect will appear proper on 4:3 TV's

At half D1, video bitrate could be dropped to about 2500kbps, and at 1/4 D1, you could use the default 1400 (probably, I haven't tested).

[erik]

My PVR150MCE records in 720x576 in gbpvr
I used pocket_divx to do the calculation

Could you recommend good settings?
How to read your numbers?
Like this?
1/2 D1 : 352(horizontal) x480(vertical NTSC)/576(vertical PAL)
1/4 D1 : 352(horizontal) x240(vertical NTSC)/288(vertical PAL).

[reboot]

Exactly.
I know that 352 is not half of 720, but it's the way the pixel aspect works with the frame aspect on horizontal scaling.
A true DVD aspect is displayed at 704x, not 720, thus when using half or quarter D1, 352 is the correct number

The smaller the aspect, the less bitrate needed to maintain the same quality.
A full D1 avi, would require at least 6000kbps to maintain decent qualtiy (using DivX or XviD).
Half D1 would require about half that, or 3000kbps.
1/4 D1 would require about half again, or about 1500kbps.
Because it's not a truly linear scale, half D1 should be about 4000kbps, and 1/4 D1 should be about 2000kbps.
Obviously, higher is better. You could encode to 1/4D1 at 6000kbps, and have an extremely high quality avi, but at a waste of space. You can probably encode the same source to 4000kbps and not notice much difference.
Often, a high bitrate avi, using a small aspect ratio, will look better on a monitor, using the software to make it full screen. This same avi may look horrid on a TV!
Run some tests, and use whatever aspect and bitrate look best for YOUR EYES, on the device you'll be using to watch them.

General rule of thumb:
For watching on a PC monitor, 352x240/288, medium bitrate, is usually better, even at full screen, when enlarged using the viewing software.
For watching on a TV (4:3), 720x480/576 is usually better, but only at very high bitrates.

Remember that XviD/DivX compression is much higher than mpeg-2, so even a 6000kbps 720x480/576 avi video will be a much smaller filesize than the original mpeg-2 capture.

[erik]

I always thought the bitrate was the bitrate of the compressed stream because the bitrate of the uncompressed is only dependend on pixel resolution and frame rate so you could not vary it.
I must be doing something wrong because my divx files and mpg files are the (about) the same size when with the same bitrate.
If you have processor power enough you can also encode in High Quality mode.
BIG improvement, but much to slow for my slow computer.

[reboot]

Yes, bitrate is that of the compressed stream. In this case, you are using XviD, with a FourCC code of DivX5, and i'm not sure of the xvid version, or how mencoder uses it.
Given a captured mpeg, at 6000kbps CBR, if you encode to xvid in virtualdub, you get a noticeably smaller file.

Your poor 800 must just be smoking, trying to encode the avi at high q.

[sleptoor]

This is a total newb question but is there anyway to delay the running of the plugin via post_processing.bat or anything else til the middle of the night (probably like auto_nighty does)

[KingArgyle]

If you want it to run in the middle of the night, put it in PostUpdateEPG.bat, which runs after the episode guide has been updated.