Converting 23.976fps video?

[Sakuya]

I downloaded a video that has 23.976fps. I want to burn it to VCD. I use TMPGEnc. I have an NTSC TV. So, do I leave it at 23.976fps or should I encode it to 29.97fps? Also, the video is in 720x480.

Let's say I wanted to make a non-standard VCD, an XVCD or whatever you call it and want to achieve the highest quality possible. Should I leave encode it at 720x480? Or something smaller? Will it fit on the TV screen?

[adam]

VCDs support ntscfilm (23.976fps.) Just encode at that fps and the DVD player will convert it to 29.97fps during playback. This is much higher quality than physically converting it to 29.97fps yourself.

If you are planning on encoding this at VCD compliant bitrates, ie: 1150kbits than you definitely don't want to use that high of a resolution. The higher your res, the higher bitrate you need to represent that sized image. 720x480 needs at least 3mbits and really needs more like 4.5-5mbits to really be high quality.

My recommendations are:

1.5mbits and under=352x240/288
1.6mbits-3mbits=352x480/576
3mbits and higher=720x480/576

The video contains an aspect ratio flag, which instructs the DVD player to stretch the video to fit your screen, and to do so in the set proportion so that the image is displayed correct. So regardless of your resolution, the picture looks the same ie: same aspect ratio, but the higher the resolution you use the more detail the picture has. Of course anytime you use non-standard settings than any number of things can go wrong on any given DVD player.

[Sakuya]

If I did decide to ues 720x480 and I used a "Constant Quality", what should/could the maximum bitrate be? And what is mbits?

[pijetro]

Ummm, am I missing something here??? It's been a while since I've done this, but isn't VCD resolution a firm 352x240 with a bitrate of 1150kb/s video with 224kb/s audio..Perhaps you can up the bitrate to create an XVCD, but according to your post, you want VCD. I'm under the impression that you can't alter the framesize, even for XVCD. If you encode your existing video as is, then you'r gonna get major interlacing...

[adam]

mbits=1000kbits. Its the bits per second, or what is more commonly referred to as the bitrate.

As pijetro noted, anything other than 352x240/288 @1150kbits will not comply with the VCD standard. Anything using mpeg1 but deviating from this standard is commonly referred to as an XVCD, and so by definition the bitrate and/or resolution can literally be anything. Feel free to experiment with these settings however you like, just don't be suprised when problems arise. My understanding of Sakuya's post was that he/she wanted to make an XVCD, but was wondering if 23.976fps still complies with the VCD standard.

When it comes to XVCD and the bitrate you choose it really all boils down to how much machine x will play. Machine x may just mean your own dvd player, or it may include those of your friends and family. The higher you raise your bitrate the less chance the XVCD will play on any given player. You are just going to have to run some tests and decide for yourself how far outside of the standard you are willing to go.

In any case, interlacing should be no different for a VCD or an XVCD regardless of what resolution you use. Mpeg1 simply does not support interlacing at all, so unless you deinterlace you run the risk of getting interlacing artifacts regardless of what resolution you encoded to. For most sources, however, simply encoding an interlaced source to mpeg1 will throw out one field or the other, and the result is a progressive image with no visible interlacing artifacts. Anyway, if this is a downloaded avi then there is a 99% chance that it is progressive.

[Sakuya]

What do interlacing artifacts look like? Also, this is weird. Remember how I said that in Virtual Dub, the AVI says it is 23.976fps? Well, when I loaded it into TMPGEnc, at the bottom it says 30fps. Is that info bar at the bottom accurate? Should I encode it at 30fps or should I change it 23.976 or 29.97?

[adam]

Interlacing artifacts are when you can see the interlacing, basically the horizontal white lines running through the picture. The picture will have a comb like effect. You can also get other artifacts which appear where these white lines are, even though you can't actually see the white lines themselves.

The info at the bottom of TMPGenc is simply the output settings. This has nothing to do with your source. Avi's don't support pulldown flags like mpeg2 does. If something, ie: VirtualDub, reports it as 23.976fps than believe it.

Just set the fps to 23.976fps and the fps will be fine.

[Sakuya]

How will the different fps make a difference in the video quality? I did a test with a part of a video using 30fps... ..nothing happened...it's just the same as a normal video. What is supposed to happene?

[adam]

If your source is 23.976fps and you simply change the fps to 30 than 1 of two things will happen, depending on your settings. Either 6 frames will be repeated every second and you will get riduculously jerky playback, or your film will be sped up by 2%0 and everything will be moving extremely fast.

If you perfrom a telecine (the proper way to convert 24fps to 30fps) ie: repeat fields in a specific pattern, then you won't notice any difference in movement, however, you have now created an additional 20% more frames which were not present in the original. When you encode video you distribute bits to each frame, and the amount of bits you can use depends on the capacity of the media you are burning to. So, by converting to ~30fps you now have the same physical result, 30 frames per second of video, but you are allocating your bitrate to each of these frames, so your bitrate is effectively decreased.

If you just encode to 23.976fps the telecine process will be done on the fly by the dvd player. Instead of distributing bits to those additional 20% of your frames, you only have to encode the original ~24. This is much more efficient and, incidentally, it is how almost all commercial NTSC DVDs are made. If your source is 23.976fps than just keep it that way.

[Sakuya]

If that is so, I just wasted 5 hours of encoding time! I should've waited for your response first. But the test video I made is pretty smooth and nothing seemed to speed up or unusual. It's exactly like the source video only with less quality.

[Sakuya]

That's weird. I encoded the second part in 23.976fps but it's doing the opposite of what you said Adam! When it was 30fps, it was playing pretty good on the TV. But in 23.976, it had jerky movements and the audio was choppy. While if you view the second part on the computer, it doesn't suffer from those problems...should I re-encode the second part to 29.97? That's my most widely-used fps for all of my videos.

[vhelp]

@ Sakuya..

Are you SURE vdub is saying your source is 23.976 ??

Cause the symtoms you described sounds like it not, and that it's actually
29.970 fps. Did someone TELL you it was 23.976 elsewhere's ?? They
were wrong, if they did. My guess is what you were missinformed.

Anyways..
What are the contents on your .AVI ??
* Is it a Movie, or
* is it a TV show
* or some divX (perhaps improperly encoded) ??
* is it NTSC or PAL

For now, try and encode it w/ 29.970 fps and see how it plays smoothly
or not.

-vhelp

[Sakuya]

It's a 52-minute movie file. I opened it in VDub, and then went to File Information. I'm sure it said "23.976fps". And it says the decompressor is DivX MPEG-4 Video Codec or something like that.

Also, I'm currently encoding it to 29.97fps. At the same time, I opened VDub to watch another AVI file. Because last time, when I used Divx Player 2.0 to watch it while encoding, I noticed that the encoding process seemed to pause. So I'm using VDub to watch it. After I finished watching it, I noticedin TMPGEnc that the "Remaining Time" shot up to 16 hours! And I closed Vdub and now it is going down. Do other active programs make TMPGEnc slow? This is so frustrating...

[vhelp]

@ Sakuya..

Do other active programs make TMPGEnc slow?

yes.

Especially, if you have a slow pc, you should ONLY have TMPG running.
-vhelp

[Sakuya]

That's not fair! It's already 9PM and it still got 7 hours to go!!! *panic* What'll I do? I can't save it?! I can't leave the computer on. I have to pay the electric bill. Mooooo.....

[Sakuya]

The clip I aborted yesterday, I used it as a sample clip. It was in 29.97fps and it played perfectly! Very smooth! Even slightly better than 30fps! So I guess 29.97fps is like the most commonly used fps?

Also, where do I find the accurate fps for an AVI file?