VirtualDubMod Zones problem

[peterhun]

Hi all, I'm not sure if I am doing this correctly. I'm using a single VOB as my source, using VirtualDubMod to Xvid avi.
The first 4 minutes of the AVI are really blocky whereas the rest of the video is quite good (the subject is in motion).

I thought I'd try using Zones to put a higher quality on the leading 4 minute segment of the conversion and resume normal quality for the remainder. So I have chosen a Weighting of 0.30 for the first part and I assume that the remainder will be 0.70 to give a total of 1.0 (100%) for the whole video file. Am I right in this approach? I just pulled this figure from nowhere really, just thought that 30% of the total would be dedicated to the leading part.

Anyhow, it still didn't turn out any better.

[poisondeathray]

Are the macroblocks from xvid encoding, or are there source problems ? Another approach might be to prefilter the source or that section, if there is an issue with the source VOB

EDIT; sorry I'm wrong about zones in xvid, you're correct. I was thinking of zones in x264, where it's expressed as a rate factor multiplier on the zone

Why not use quantizer based encoding ? Do you need an exact file size ?

[peterhun]

The VOB is from my dvd and is good visually. The movie is 2 1/2 hrs and the blocking is as a result of conversion to avi (1500Kb/s sampling, I think, can't remember now). The file size ends up at 1.6GB without any degradation but I wanted a smaller size file.

I can get a reasonable pic down to 1GB but the first 4 mins is blocky at this size because of the content of that section.

So I want to improve this section (higher quality) only. The audio I'm happy at keeping mp3 128k.

[DarrellS]

This is the downside of mpeg4 part 2 (DivX and XviD). No matter how high the bitrate, you still get macroblocking in certain dark scenes. I used to encode my AVI at 4000kbps to try and avoid this but I still got macroblocking. I now encode to Mpeg4 part 10 (h264) which seems to be able to encode at a much lower bitrate without macroblocking but if you go too low on the bitrate, you'll get macroblocking also.

There is no real reason to try and encode everything to fit on a CD these days. With the price of large hard drives and the availability of hardware media players (and even TVs) that will play H264.mkv. Besides, you can fit more videos on your hard drive if they are encoded to H264 since the compression is much better.

If you use Virtualdub 1.10.0 with the external encoder feature, then you can encode to x264/aac mp4/mkv or x264/ac3/mp3 mkv using command line encoders.

http://forums.virtualdub.org/index.php?act=ST&f=3&t=18840&

[manono]

I thought I'd try using Zones to put a higher quality on the leading 4 minute segment of the conversion and resume normal quality for the remainder. So I have chosen a Weighting of 0.30 for the first part and I assume that the remainder will be 0.70 to give a total of 1.0 (100%) for the whole video file. Am I right in this approach?

No, you're not right at all. 1.00 gives the whole thing equal weight based on the settings. If you want a certain section to have better quality than the rest (in your case, frames 0-5459), you use a figure greater than 1.00. The bitrate of the remainder will be adjusted downward (unless you also set zones for it) so that you come out in the end with the filesize you want. So, maybe set that first zone at 1.3 and set the rest for 1.00.

By the way, the whole idea sounds a bit screwy to me. Ordinarily, most people want the video to have even quality throughout. I never touch the zones (unless it's to give the end credits lower quality) and usually do CQ encodes at a fixed quant (3, usually).

[davexnet]

Is the OP doing single pass encoding? Perhaps forget about zones and do either 2-pass, or use CQ mode.
Seems like single pass fixed bitrate is the worst of all choices.

[poisondeathray]

I thought I'd try using Zones to put a higher quality on the leading 4 minute segment of the conversion and resume normal quality for the remainder. So I have chosen a Weighting of 0.30 for the first part and I assume that the remainder will be 0.70 to give a total of 1.0 (100%) for the whole video file. Am I right in this approach?

No, you're not right at all. 1.00 gives the whole thing equal weight based on the settings. If you want a certain section to have better quality than the rest (in your case, frames 0-5459), you use a figure greater than 1.00. The bitrate of the remainder will be adjusted downward (unless you also set zones for it) so that you come out in the end with the filesize you want. So, maybe set that first zone at 1.3 and set the rest for 1.00.

That's the way it is in x264, a bitrate multiplier on the zone

eg. So 1.3 would be 130% the normal allocated bitrate for that section

But I edited my post after seeing this xvid guide
http://www.divx-digest.com/articles/xvid_setup_page3.html

The "Weight" option allow you to specify a weight on the chosen bit-rate. A "Weight" setting of 0.15 will mean the zone will only get 15% of the bit-rate of the main movie.

I guess I was confused about term "main movie" in that article. In x264 , the multiplier applies to the zone, not a percentage of the main movie.

So manono, you're saying it works the same as x264 ?

[manono]

I haven't checked the article, but 0.15 is often given as a figure to apply to a movie's end credits, distinct from the 'main movie'.

I have no idea how x264 works, pdr. Sorry.

[peterhun]

Can a divx standalone play x264. I've always used avi and put 5 on a dvd disc, so I've never messed around with x264 encoding.

ps. thanks for the url, I searched everywhere that I knew but couldn't find any mention of Zones.

[manono]

Can a divx standalone play x264.

Usually not.

[DarrellS]

My Philips 5990 was obsolete a week after I bought it over two years ago. I bought the WDTV a week after and haven't watched hardly anything on the Philips since. I do use it to play my audio CDs through my receiver.

I encode most of my movies to H264 and watch them on the WD off of a Mybook.

If you tried putting less videos on a single DVD-R then you probably would not have the macroblocking issue. Especially if the movies are over 2 hours in length. You don't have to use the most expensive discs you can find when burning Data DVDs

Ideally, one 2 1/2 hour XviD at just under 4000 kbps will fit on a DVD-R. To me, it doesn't make sense to compress the hell out of a DVD so that you can fit 4 or 5 of them on a single DVD when you could watch the movie in it's intended glory off of the original DVD. If you're going to go through all of the trouble to back up a DVD then you might as well get as close to the original quality as you can. If you're just after low quality videos that will fit on a CD then you might as well just download them off the internet.