MPEG-1 Question

[Chappy81]

I was doing a search in this forum, and I read that MPEG-1 is progressive scan ONLY. Does this mean that it cannot be changed to interlaced in any way??? I want to be able to watch it on a TV, but the playback is jerky, and I assumed that interlacing it would help solve the jerkyness. (That is, assuming the source is progressive, I'm not 100% sure on that one.) Also, would doing a pulldown or changing the field order help??

I've been researching this for a week now, and I'm not any closer to getting this movie to play smoothly.

Any more help would be appreciated.

[andkiich]

MPEG1 is not interlaced because of the resolution. VCD res is 352x240(for NTSC). DVD resolution is 352x240/352x480/704x480/720x480. It's the second half of those specs that wil make it interlaced or not. If you re-encoded the MPEG1 to MPEG2 and made it 352x480, then it would be interlaced. However, the video might look like crud after you are done.

It's probably not the interlaced/progressive thing that is making the video choppy. It's probably media, encoding or something in the process of making the MPEG1 file.

PS - since there is no interlacing, then field order doesn't come into paly either. The field order is there only to determine which of the 2 fields is displayed top or bottom. Since you don't have multiple fields with the resolution you are using, then field order doesn't matter.

[Chappy81]

Thanks for your reply! Ok, so I started off with an AVI file, and changed it to MPEG using TMPGEnc. Since it's an MPEG-1 file, I know that it must be progressive scan and can't be changed right?? So, when I play the file on my computer it works perfectly, but on the DVD player it ends up choppy. Maybe the problem then is with the fps. I know the video is 25fps, but TMPGEnc doesn't have that option. (I think for the choppy video I chose 29fps) Is this why the video is jerky? I need to change the fps???

[Nelson37]

I'm gonna disagree with andkiich here. There is nothing about the resolution that makes a video interlaced. I have made 720x480 non-interlaced MPEG-1 video, and most DVDs are 720x480 progressive, though MPEG-2.

The MPEG-1 standard does not support interlacing in any way. Resolution, however, can be up to 4096x4096.

MPEG-1 used on CD or DVD is only standard at 352x240, though higher resolutions will often play. The FPS is supposed to be 23.9xx, and the pulldown flag is not required though some players seem to need it.

An MPEG-1 can be created at any FPS. If while converting your AVI you changed the frame rate from the original, this is the cause of the jerkiness. If the original is some odd number like 15 or 20, you're in for some real fun.

[wulf109]

Tmpeg will encode a vcd as interlaced,I've done it many times. Load the vcd template and then unlock it. Then select settings,system and change to mpeg2SVCD. Then change the template to interlaced and go back to system and change it back to vcd and it will remain interlaced.

[Sulik]

Maybe it made you feel good that the TMPGENC UI let you select "interlaced" and "VCD" at the same time, but this is just plain impossible, for two reasons:

1) VCD is 352x240(NTSC) or 352x288 (PAL), thus can only contains a single field of vertical resolution. It cannot even contain two interleaved fields, so forget about supporting interlaced frames.

2) MPEG-1 DOES NOT SUPPORT INTERLACED! The progressive_sequence / progressive_frame flags required for signaling interlaced content and the features that come with only exist in MPEG-2 specific headers, not present in the MPEG-1 bitstream. If youadd these headers, your sequence automatically becomes MPEG-2 (these same headers are also used to differenciate MPEG-2 from MPEG-1)

So, can you encode interlaced video as MPEG-1 ?

-Option #1: deinterlace the video when encoding to MPEG-1. Obviously, the sequence will no longer be interlaced after this step, and all frames will be progressive.

-Option #2: do not deinterlace, and encode it as MPEG-1 anyway, marking the frames: that will work, but will not playback correctly on a progressive display (MPEG-1 frames are inherently progressive, thus not deinterlaced), and exhibit much more compression artifacts when there is motion compared to if the same sequence was encoded as MPEG-2 interlaced (interlacing artifacts will show up as HF noise in the encoder, requiring a much higher bitrate for the same level of quality)

[Chappy81]

An MPEG-1 can be created at any FPS. If while converting your AVI you changed the frame rate from the original, this is the cause of the jerkiness.

I know the original frame rate of the AVI is 25fps. But TMPGEnc does not have this option. So which format do I choose when I go to convert it??? NTSC or NTSC Film??

[VCDHunter]

An MPEG-1 can be created at any FPS. If while converting your AVI you changed the frame rate from the original, this is the cause of the jerkiness.

I know the original frame rate of the AVI is 25fps. But TMPGEnc does not have this option. So which format do I choose when I go to convert it??? NTSC or NTSC Film??

Neither - use the PAL template. TMPGenc has the templates for PAL encoding as well as NTSC & NTSC Film.

[Chappy81]

I don't think I can use the PAL template, because my DVD player does not support it. (I have checked the manual and the remote) What can I do now????