Conversion of MPEG2 files to smaller size

[tonyaldr]

I've captured some MPG2 films from VHS using software that can only do 720x480. I'm trying to convert down to 352x240 using TMPGenc Plus so as to get smaller file sizes, but the files are still quite large! 30 mins is over a gig even at the converted size, yet when I've recorded from my Panasonic DVD-RAM set-top box the files are a lot smaller. Here's the data from a file recorded on the Panasonic courtesy of Mediainfo
General
Format : MPEG-PS
File size : 371 MiB
Duration : 30mn 52s
Overall bit rate : 1681 Kbps

Video
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, Matrix : Standard
Duration : 30mn 52s
Bit rate mode : Constant
Bit rate : 1341 Kbps
Nominal bit rate : 8000 Kbps
Width : 352 pixels
Height : 240 pixels
Display aspect ratio : 4/3
Frame rate : 29.970 fps
Standard : NTSC
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 3.160

Audio
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Duration : 30mn 51s
Bit rate mode : Constant
Bit rate : 224 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Resolution : 16 bits
Video delay : -66ms

I chose the audio settings and the video settings from above, but I think my trouble is choosing the video bitrate. What is the difference between the "nominal bitrate" and the other "bit rate" reported above? I've been trying VBR and using 8000 (from the figure reported above) as the average. Thanx!

[redwudz]

Changing the frame size won't have that much effect on filesize unless you also reduce the bitrate. You can use a bitrate calculator to see what size it will be. Try the VideoHelp Bitrate calculator.

That looks like you may be using MPEG-2 format. At that low of bitrate, it won't look too good. You could try 1/2D1 or VCD format. At VCD bitrate (1150Kbs), 80 minutes MPG-1 will be about 700MB.

[poisondeathray]

If filesize is an issue, did you consider using a better compression codec than MPEG2 (such as XviD or x264)? Or is there a reason that you are sticking to MPEG2?

[tonyaldr]

The capture software just does MPEG2 and I thought it might be a good idea to keep it as that, in order to easily create DVDs to share with those folks who want to use set top boxes rather than their PC. Thanx.

[minidv2dvd]

why would you re-encode video that is already dvd spec to a non-dvd spec in order to make dvds?

the logic eludes even this simple mind.

[yoda313]

why would you re-encode video that is already dvd spec to a non-dvd spec in order to make dvds?

the logic eludes even this simple mind.

The poster is trying to make them smaller. It is also mentioned a desire to share with as many people as possible hence the reasoning to keep it mpeg2 I suppose.

However I would agree with poisondeathray - either divx/xvid or perhaps wmv would be a good alternative. Excellent compression and you get decent picture quality assuming you don't use too low of a bitrate.

For sharing you would be better off using divx/xvid or wmv as mentioned. - edit - if you use divx chances are the people you are sharing with it MIGHT have a divx capable dvd player. If they own an xbox 360 or ps3 than they can play standard divx. - dvd players that play wmv are more rare.

[tonyaldr]

I don't think I'm advocating re-encoding to a non DVD compliant codec. Unless I'm mistaken and you can correct me, I'm just re-encoding so that 4 hours would fit on a DVD as opposed to 1 or 2 hours by staying with MPEG2.

[yoda313]

Than you will need to do what redwudz suggested - use 1/2d1 resolution at a lower bitrate.

Just be aware that of course you will lose some quality in the reencode.

[redwudz]

Your Panasonic is actually going lower than 1/2D1 at 352 x 240. The advantage of a lower framesize is you can use a lower bitrate and still retain some quality. I personally wouldn't go below 1/2D1 at about 1500Kbps, but a lot depends on your source quality. A noisy video does not compress well.

These are the compatible framesizes for NTSC DVDs:

720 x 480 pixels MPEG2 (Called Full-D1)
704 x 480 pixels MPEG2
352 x 480 pixels MPEG2 (Called Half-D1, same as the CVD Standard)
352 x 240 pixels MPEG2
352 x 240 pixels MPEG1 (Same as the VCD Standard)

The above is from 'WHAT IS' DVD to the upper left on this page. It details the DVD specifications, format and structure. If you adhere to those, you should have a DVD compatible video.

But if you want four hours to fit on a DVD... And I don't believe you mentioned that number before... This from a bitrate calculator:



About 2300Kbs will get you there with a 4.37Gb file size with a bit of room to spare. At that bitrate, 1/2D1 would still be a good choice, as that is at the bottom of full D1 quality. You can use variable bitrate encodes, but you will need to make two passes to get close to that target bitrate. VHS caps often have a lot of noise, so I would try a short encode of a representative sample of about 5 - 10 minutes of your video and see if the results are acceptable.

[tonyaldr]

Thanx for the advice! I'll check it out!

[redwudz]

I should add, 1/2D1 may be a bit of a pain to set up in TMPGEnc Plus. But you can make a new template so you can use it a bit easier in the future. It's been a while since I used TMPGEnc Plus, so I don't recall it all. But 1/2D1 is still a good choice. For 5 to 6 hours, MPEG-1 at VCD bitrates is the next step down.

Yes, I know, a lot to absorb, but once you get a good encode with your material, it will be a lot easier next time.

[minidv2dvd]

why not set your capture software to 2-3000kbps vbr and keep it at dvd spec 720x480? no additional loss of quality from the extra encoding steps and it's dvd compliant to boot.

[tonyaldr]

The software doesn't let you do that. It's pretty barebones. Thanx anyway.

[minidv2dvd]

if it's a capture card in your pc try using different software, you don't have to use the stuff that comes with it. personally i capture with powerdirector when using the kworld card in my comp. it allows the audio to be captured to ac-3 and the video to mpeg-2 in cbr or vbr at any bitrate you choose. i import the files it creates directly into dvdlab to author dvds.