Too high bitrate after pulldown

[tabachanker]

Hi,

I have a question about converting a Divx video to DVD.

First, my source video is 24 fps. I convert it using a guide on this site. To do so, I use AVS, CCE and DVD-Lab to author the DVD. I use DVD-Lab also for the pulldown process to change my video to 30 fps.

The DVD I make that way plays well on my DVD player. But at some places, the video kind of stutter for about 1 second each time. It can happen about 4 or 5 times for a 20 minutes video. The way it happens made me think it was a "too high bitrate" problem. I think I'm right.

I used a software called "Bitrate Viewer" to see the bitrate on my video files. The orginal mpeg file created by CCE is perfect, exactly what I asked (for example, 6500 average bits/s, 9000 max). This is the 24fps file. But the video file which I added the pulldown flag isn't correct. It peaks at about 10500 bits/s. Now I understand that using the pulldown flag adds 6 frames in a second. So I think this is normal. But no guides seems to talk about this. I tried re-enconding my video file with a max bitrate of 8000. Now, it only peaks at 9500 which is ok. But I don't think this is the best method (guessing what the max video bitrate will be after the pulldown.)

Is there something I'm missing?

Thanks a lot for your help

EDIT:
Forgot to tell that I tried my DVD with powerDVD and it playbacks without any stutters (I checked the places that did it on my DVD player)

[Soopafresh]

All too common of a problem with VBR Mpeg2 encodes. CCE is usually pretty good at keeping encodes within spec, however. I think 8000 is pretty darned good for a Standard Def DVD, personally.

You can encode at CBR and it won't peak. Problem is, your file will be much larger. Maybe even much, much larger.

[tabachanker]

Thanks for your quick reply. CCE is really great for encoding within the parameters I set. I use it now over TMPGENC because of that (TMPGEnc goes too often over the max I set). CCE just doesn't calculate the pulldown process that I have to do after the actual encoding.

So if this behavior is normal, I wonder why all the guides I've read talk about putting 9500 bits/s max in all encoding. Those guides even talk about using pulldown.exe after the encoding if the source is 24fps.

Is the best way, to avoid this problem, to lower the max setting to 8000 (or lower)?

[manono]

Hi-

Is there something I'm missing?

Yes, don't trust BitRate Viewer to give you accurate numbers. It gives me figures of up to 12000 sometimes. CCE doesn't go over what you set it for (unlike some encoders), and I always give it the max possible (often up to 9800), and don't have the problems you experience. All DVD players should play to the max allowed, and your authoring app should reject it, or at least warn you, if the bitrate is over the amount allowed. However, I don't use DVDLab, so I have no idea what it does. There could be a number of reasons why you get stuttering, but I don't think that excess bitrate is one of them, when you set your max video bitrate for 9000.

[tabachanker]

Yes, don't trust BitRate Viewer to give you accurate numbers. It gives me figures of up to 12000 sometimes. CCE doesn't go over what you set it for (unlike some encoders), and I always give it the max possible (often up to 9800), and don't have the problems you experience. All DVD players should play to the max allowed, and your authoring app should reject it, or at least warn you, if the bitrate is over the amount allowed. However, I don't use DVDLab, so I have no idea what it does. There could be a number of reasons why you get stuttering, but I don't think that excess bitrate is one of them, when you set your max video bitrate for 9000.

Like I said in my previous post, CCE is encoding perfectly within the parameters I set. It's when I use the pulldown process (to change from 24fps to 30fps) that makes the bitrate go through the roof! Bitrate Viewer works perfectly with the original file (peek at 9000 bit/s, average 6500 bit/s). It's the video file after the pulldown that peeks at more than 10500 bit/s.

Stuttering appears exactly at the some points in any given video. I checked the time when it happens (for example, at 1:38 ). If I check with bitrate viewer, at this exact point (1:38 ), the bitrate is 10500 bit/s.

I guess what I'd like to know is: Is this normal behavior? The pulldown process adds 6 "virtual" frames every second. Since bitrate is calculated by seconds, it adds a lot of information in every second. Do DVD players actually have to read those 6 virtual frames? Do those frames count in the DVD maximum bitrate allowed? Maybe some DVD players have this problem and some doesn't. I have a Yamaha S530.

Thanks for all your help so far!

[guns1inger]

They are exactly that, virtual frames. They don't exist on the disk, and they don't take up any space. It is a flag that tells the playback device to output 29.976 fps instead of the 23.976 fps you actually encoded.

I'm at a loss as to why the bitrate would change. Try using DGpulldown on the original, then use it in DVD Lab instead. See if it changes the bitrate.

[SLK001]

Bitrate Viewer has a known bug where it doesn't use the encoded fps as the basis for its calculations (instead, it uses the displayed fps in its calculations). PULLDOWN works correctly, so trust that what you put in it will come out okay. Examine your true BR with your pre-pulldowned video. It will be exactly the same after PD.