mpeg1&2 bitrates equivalency

[4321]

OK for starters, I'm using tmpgenc plus.

I have this video clip in mpeg1 format. The bitrate is 1000kbps. I wanted to convert it to mpeg2 for various purposes and stuff. However, when I did convert it to mpeg2 at the same bitrates, the quality of the mpeg2 version was HORRIBLE.

So in the mean time, I've been converting mpeg1 clips to mpeg2 at extremely high bitrates to keep the quality of the video.

So basically, I would like to know if there's a less time consuming way of converting mpeg1 to mpeg2 using extremely high bitrates to keep the quality in check.

Thank you.

[dragongodz]

mpeg is lossy compression. so each time you recompress, especially at low bitrates, you are reducing quality. try re-encoding the 1000kbps mpeg2 re-encode and you will see it gets worse again. then recompress that and compare. :)

[4321]

So how would I go about converting without losing quality? Or is using extremely high bitrates the only way?

[dragongodz]

well depending on what the source looks like you could filter it a bit. for example if it is very noisy or grainy or blocky etc applying some light filtering could help clean that up and possibly even make it more compressable. meaning you should be able to use a moderate bitrate and retain good quality.
also of course encoding 2 pass VBR is better than 1 pass CBR. you didnt state how you were encoding so i thought i should of course mention this.

[4321]

Oh right..

It starts as mpeg1, I convert it to mpeg2 with single pass cbr. Then convert it to xvid.

I do some editing in between those conversions, and I wanted to know what would be the quickest way to get it through the process and retain the same quality.

[dragongodz]

well to retain as much quality as possible the first thing to do would be to cut out the mpeg2 step. so go directly from mpeg1 to xvid. you should be able to edit the mpeg1 as easily as you would the mpeg2.

[4321]

Hmmm, I can't seem to keep the viewing ratio to a flat 4:3 with mpeg1 though. It will only let me choose it with some ntsc and pal line.

Well, thanks again :)

[dragongodz]

maybe you want to go through exactly what you are doing and with what. otherwise its too hard to try and guess what the problem is.

[4321]

OK well, I have some clips in mpeg1 format right. They're not very well encoded. So I try to convert them to mpeg2 with high bitrates to keep the quality in check, and change the resolution and aspect ratio to a proper size. With mpeg2 I can set it to 4:3 and not some 525 or 625 line (not exactly sure what these do anyway).



Also, just a bit off but.. Is there an easy way or some sort of simple program that'll crop out pixels of the video to change the resolution a bit? Some of the clips seem to have few pixels of a black frame. I figured it'd be nice if I could crop that frame out and have just the video, that'd keep the resolution a bit lower.
Of course it'd have to be a multiple of 8 or whatever it is.

What I did before was center the video, change the resolution and re-encode it. It worked. However, when I tried playing it, there was this big green vertical bar on the right side of the video. It's as if amount of the video I cropped out was being filled in with a green vertical bar.

Oh and I'm only using 2 programs if it matters. TMPGEnc and VirtualDub.

[foxyshadis]

You can just mux your mpeg1 videos into .mkv. It supports aspect ratios, clipping windows, and that other good stuff. Then you lose no quality and waste no time re-encoding everything. (mmg shows AR options, but you have to add cropping to the command line yourself to enable it).

And yeah, some codecs have an unfortunate habit of padding non-mod16 with green junk when encoding, so you might need to crop even more. Other encoders like HC and Quenc don't, afaik.

Now, if you're transferring it to DVD or broadcast, you'll probably need to clean it up in avisynth (or virtualdub filters if you have to) anyway, just because it's silly to permanently transfer a bad source. You might as well fix it if you're going to be re-encoding anyway.

[4321]

You can just mux your mpeg1 videos into .mkv. It supports aspect ratios, clipping windows, and that other good stuff. Then you lose no quality and waste no time re-encoding everything. (mmg shows AR options, but you have to add cropping to the command line yourself to enable it).

And yeah, some codecs have an unfortunate habit of padding non-mod16 with green junk when encoding, so you might need to crop even more. Other encoders like HC and Quenc don't, afaik.

Now, if you're transferring it to DVD or broadcast, you'll probably need to clean it up in avisynth (or virtualdub filters if you have to) anyway, just because it's silly to permanently transfer a bad source. You might as well fix it if you're going to be re-encoding anyway.

Umm.. I don't quite understand what you said. There's a lot of synonyms I'm unaware of. And procedures mentioned as well. =/

Things like muxing to mkv and losing no quality? how would I do that and then going back to xvid/avi? I also have never used avisynth before. or vdub filters. not sure where to get the ones I would need. I already checked this site's filters section.

[foxyshadis]

What is the end result of the conversion? Are you going to end with an xvid avi? (Auto Gordian Knot or GK is the best simple way to get there, if you need cleanup.) A dvd? A project file to work from for editing? Do you just want to watch it? That'll help with recommending a good method.

[dragongodz]

What is the end result of the conversion? Are you going to end with an xvid avi?
from earlier in this thread
It starts as mpeg1, I convert it to mpeg2 with single pass cbr. Then convert it to xvid.

as i said i would completely cut the mpeg2 encoding step. you mention you use virtualdub, well that can decode mpeg1. so why not import that straight to virtualdub, use its filters to resize etc and encode ?

if you need to do more work on the source than what virtualdubs filters provide then definatly look at avisynth.

[4321]

Haha... I didn't know about all these integrated filters in vdub. I actually didn't know there were even anything integrated. :P

Well, learned something there. Thanks.