Can Audio Gordian Knot be used to convert files/compress?

[videofan70]

Here's the problem I'm having

I'm trying to convert an hour long 2.84 gig MPG file to a 350 megabyte avi. I've tried using format factory, but it doesn't appear it allows you to specify how large a file size you would like the output file to be. Also, there's some discrepency with size.

For example, I have

1 A 55 minute Mpg video file that is 2.8 gigabytes big
2. A 56 minute video which is 2.84 gigabytes big

When I used Format Factory to resize them (I don't remember what the resulting avi's were under the drop down box at the top, but I used the same setting for all of them) the resulting files I got were

1. One 585MB
2. One 890MB

I like to fact the AutoGk lets you specify how big you would like the files to be. Anyway, here's the error I am getting when I try to convert the file

Microsoft C runtime library

Runtime error

Program C:\Progra~1\AutoGk\Vdubmod\Virtua~1.exe

This application has requested the runtime to terminate it in an unusual way. Please contact the application's support team for more information.

I'm wondering, though if I should aim at 250MB per hour of video for an AVI? I do have some other AVI's which are smaller at 40 minutes and are only 189MB's.

]lso, I recorded 10 episodes of a show from my DVR to my computer with a capture device. They are all MPG files, which I want to convert to AVI's to save space. Do I need to/should I save those MPG's. They are huge files, and if there is way to convert them back from AVI's to MPG's (for some reason) with no loss of quality from it's original MPG, then I'd rather do that. Basically, is any information lost/discarded when you convert to another format, making a smaller file, or just compressed, like letting air out of a balloon, you can just blow it back up to it's original size.

[DB83]

A few questions here so I'll try to give a few answers.

Firstly, file size = runlength*bitrate. I suspect that the two examples you quote are not exactly 55 and 56 minutes but the longer vid will be bigger.

Considering the above rule, 250mb for 1 hour using xVID or diVX (the only compressors that autogk use) is way to small. It does depending on the initial quality of your source but you need to aim for 700/800 kbps MINIMUM. To go down low at 250 meg you will have to reduce your video dimensions (height/width) susbstantially. Using my bitrate guide, you will have a file of 350-400 meg (use a bitrate calculator or xvids own for the exact result)

All compressions result in a loss of quality. You can resuce that 3 gig file down to whatever and you can re-encode that file back to a 3 gig mpg. BUT you can not recover the quality that you have lost. It may, in your eyes, look the same but it will not be the same.

[videofan70]

Here are the two USB capture devices I have

An EZcap 148 (the real one, not the fake someone has started selling. It wasn't available in the US, I had someone in England send it to me)

http://szforwardvideo.en.alibaba.com/product/437796742-50120560/USB_Video_Grabber_with...EzCAP148_.html

and This:

http://www.meritline.com/mygica-ezgrabber-2-usb-2-0-video-capture---p-41210.aspx

I've mainly been using the EZ grabber 2. The EZcap I believe I used before, but it's not working quite right, now. I can either output video from my cable converter/DVR directly, or TV, or a VCR. What is it you want to look for to see what kind of quality you will get? I'm guessing the specs for all 3 devices perhaps? Or maybe just the specs for my cable box if I am outputting video from that?

Yes, guess I have to learn how codecs work. Take for example in 2 your example, I recorded something from my set top box to my computer at 800kbps (bytes or bits? I did bytes for this example). 800000x60x60= 2.88 gigabytes, then it is compressed.

Take for example compression when something is made into a zip file to make for a faster download, it can be uncompressed and be exactly what it was before. Why can't video?

[DB83]

Your math appears wrong.

I assume you capture with the easycap in to mpeg2. A one-hour recording at 8000kbps (kilobytes) will come out at 4 gig (a little less depending on the audio format)

At 5500/6000 kbps you have a video file of up to 3 gig.

You simply can not capture mpeg2 at 800 kbps. Well if you did, your video look like sh*t. The 800 kbps I quoted is for xVID.

Mpeg2 is already compressed. XVID will compress ferther but to do that it must throw away detail ie quality. Google about video compression and try to understand that basic info.

[sanlyn]

.I'm trying to convert an hour long 2.84 gig MPG file to a 350 megabyte avi.

At this point, I ceased to be amazed. It's a genetic trend.

[videofan70]

[QUOTE=DB83;2207139]Your math appears wrong.

I assume you capture with the easycap in to mpeg2. A one-hour recording at 8000kbps (kilobytes) will come out at 4 gig (a little less depending on the audio format)

At 5500/6000 kbps you have a video file of up to 3 gig.

You said 800 kbps, k-kilo=1000, so if it were 800 (but you said that would look bad so I don't want to use it) 800kbps, 800,000 bytes

[sanlyn]

They are huge files, and if there is way to convert them back from AVI's to MPG's (for some reason) with no loss of quality from it's original MPG, then I'd rather do that. Basically, is any information lost/discarded when you convert to another format, making a smaller file, or just compressed, like letting air out of a balloon, you can just blow it back up to it's original size.

Totally incorrect. No way. MPEG and DivX compression are not like ZIP or RAR compression. Going from lossy compressed MPEG to more lossy and tighter DivX compression generates garbage. Try to "blow that up" to another round of MPEG compression, and you don't just blow it up, you blow it away into complete trash.

However, there are several free converters/compressors listed in the tools & software section of the forum that let you reduce a 2.5 GB MPEG2 to about 200 MB avi with any of several suitably destructive compression schemes. I've seen it done in other posts, and recently. Browse thru some MPEG->AVI tools so that you can discuss possible choices in more detail.

Caution: Don't discard your originals.

[AlanHK]

Take for example compression when something is made into a zip file to make for a faster download, it can be uncompressed and be exactly what it was before. Why can't video?

You can, that's called lossless compression. e.g. Huffyuv.
You get files of tens of gigabytes instead of hundreds of MB if you do that though.

That's why almost all video distributed -- whether MPEG, AVI, MKV, is compressed in a lossy way.

Similar to simple images: BMP vs JPG, or audio: WAVE vs MP3.

[hech54]

An EZcap 148 (the real one, not the fake someone has started selling. It wasn't available in the US, I had someone in England send it to me)

http://szforwardvideo.en.alibaba.com/product/437796742-50120560/USB_Video_Grabber_with...EzCAP148_.html

That's a fake. This is the real one:
http://www.ezcap.tv/

[hello_hello]

[QUOTE=videofan70;2206894]
I like to fact the AutoGk lets you specify how big you would like the files to be. Anyway, here's the error I am getting when I try to convert the file
[QUOTE]

If the problem persists after a reboot, try replacing the version of VirtualDubmod which AutoGK installs with the last version which was released. Just navigate to the VDubMod folder in the AutoGK installation directory, delete everything in it, and replace them with the files from the newer version. VirtualDubMod_1_5_10_2_All_inclusive.zip

On the subject of converting.... the discussion on potential quality loss aside (which is all correct)..... no two videos can be compressed by the same amount at the same quality. Even if the original files are around the same size, the re-encoded versions will invariably be different sizes for the same quality. Therefore if you compress them choosing the same file size each time, the quality will be different. That's probably why you're getting such different file sizes using Format Factory, assuming the output resolution and encoder settings are the same each time.

The idea behind AutoGK, if you leave everything in auto mode while selecting a file size, is it will make any necessary adjustments to give you the best quality it can. It might adjust the resolution, change resizers and audio type or adjust encoder settings, but it does a pretty good job at maintaining quality.

The optimum file size/compression/quality ratio for xvid is around 70% to 75%. When it comes to running a single pass encode AutoGK defaults to 75%. Once again if you use AutoGK to run single pass encodes the output file sizes will vary considerably even if the output resolution and video durations are the same.