PocketTV Team

We found ways to make very high quality VGA-resolution MPEG's (can be played with PocketTV or Betaplayer on the Pocket PC, and by WMP on the desktop) at relatively low bitrate, using some advanced features of tMPGEnc (a free MPEG converter available from www.tmpgenc.net ), combined with some other tools and techniques.

The result is DVD-quality at 1.7 Mbps or less (i.e. 2 to 3 times lower bitrate than DVD).

You can see one example here:

http://pockettv.com/mpg/vga/5e-640x480-1.7Mbps-v3.mpg

If you compare the file above with our previous demo file, you will see a noticeable improvement in quality with the same file size (in the new file, there is no blocking artefacts in the fast motion scenes).

We can tell you how we produced this hi-quality demo and provide the templates that we have used, and you should be able to generate MPEG files of the same quality from your DVD's (one movie will fit in a 1GB card).

Depending on the type of video contents, this quality can be achieved with even lower bitrates (e.g. 1.4 Mbps).

Please have a look at our test file, and if you are interested to know how we achieved this, let us know here.

Enragin_Angel

I would rather create xvid or divx encodes at around 800Kbps that achieves quality similar to that vid you just pasted.

XviD settings
Single pass:
consecutive b-frames set to 2
i-frame quantizer 2-4
p-frame quantizer 2-5
b-frame quantizer 2-8
the rest of the settings left as default

You can get a decent looking encode that would fit a 1GB SD card easily. A one and a half hour movie would be around 700MB. And since divx and xvid work on pockettv and betaplayer, it's no problem. I would rather stick to more compressible codecs than MPEG-1 or MPEG-2. They are very good at retaining quality in low bitrate conditions.

PocketTV Team

We know that you can gain about 30% in compression using MPEG-4 - not 50%, though. I'd love to check what bitrate can achieve the same quality with XViD, using the same source, but I thing it will require at least 1 Mbps, i.e. 800 Kbps will not be as good as our demo file. What Xvid encoder do you use (and what version) ?

Alternatively, we can provide you the vob for this segment. Could you encode it in XViD in VGA at 800 Kbps and post the file, to compare the quality ?

Enragin_Angel

XviD 1.1

Sure, just private message me the link to where the vob segment is and I'll see what I can do with it on my free time.

Dad

Which file format would encode back to DVD at the best quality? I know any DivX files I have which i recode back to DVD produce a pretty bad quality DVD - could I expect the same from Mpeg?

thanks

PocketTV Team

Originally Posted by Dad

Which file format would encode back to DVD at the best quality? I know any DivX files I have which i recode back to DVD produce a pretty bad quality DVD - could I expect the same from Mpeg?

It's no different: If the quality of your DivX or MPEG is *very* good, you can convert it back to DVD.

Assuming DVD is about 4 Mbps, you need to make your DivX at 2.5 to 3 Mbps, and your MPEG-1 at about 4Mbps, if you want to be able to convert back to DVD (MPEG-2) at 4Mbps with absolutely no loss of quality compared to the original. Naturally it depends on the encoders that you use.

irwin2

But why?
Xvid is better then mpeg1 - often more then 30% especially in low bitrates (600-800kbps) - this is important when you have 512MB, 1GB card
Try xvid 1.1 with VHQ4, VHQ for BFrames and good quantization custom table for medium, low bitrate. Effect is really good - i don't have vobs from 5elementh but i think 1MBps is enough for this sample to beat 1.7MBps mpeg-1 (70%)

PocketTV Team

> But why?

Why what ? Are you making reference to the question about returning to DVD ?

> Xvid is better then mpeg1 - often more then 30% especially in low bitrates (600-800kbps)

If you are taking about VGA resolution - yes, you will certainely get something noticeably better with Xvid at 600 Kbps than with MPEG-1 at 600 Kbps, but it will not look good in either case. Blocks will be more blurry than blocky with Xvid, but 600 Kbps is very stressed to code VGA res.

> this is important when you have 512MB, 1GB card
Try xvid 1.1 with VHQ4, VHQ for BFrames and good quantization custom table for medium, low bitrate.

At VGA ? Can you really get decent quality at full framerate in VGA at 600 Kbps ? Really ?

> Effect is really good - i don't have vobs from 5elementh but i think 1MBps is enough for this sample to beat 1.7MBps mpeg-1 (70%).

I've provided the vob to Enragin_Angel, we'll see what he can do at 800 Kbps. I'b be surprised it's better than our sample.

Again, the point of this thread is not to discuss the compression efficiency of Xvid vs MPEG-1, it's to show that MPEG-1 can be used very efficiently (some people still think MPEG-1 is only for VCD i.e. QVGA at 1.5 Mbit/sec!!!).

PocketTV Team

> i don't have vobs from 5elementh but i think 1MBps is enough for this sample to beat 1.7MBps mpeg-1 (70%)

No, 1.0 Mbps is only 41% less than 1.7 Mbps... not 70% less!

Enragin_Angel

K...I did some tests. I'm not sure why you changed the brightness on your encode...It looks like it's noon time in your mpeg encode. That scene was when bruce willis got up in the morning...so it should be dark like mine. Oh yeah, I made no attempt to correct the rainbowing and the dotcrawl that is inherent in both of our encodes.

Here is the link to an mpeg-1 quality encode at 50% size. (average bitrate 769Kbps)

http://members.cox.net/xvidcompare/5...%20quality.avi

I think the quality is pretty much the same in these two encodes. The xvid encode here may look slightly blurrier in low motion scenes but it is definitely less blocky in high motion scenes when compared to the mpeg-1 encode. I was mainly aiming at getting 50% of the filesize of the mpeg-1 clip.

Here is a better more decent quality encode. (average bitrate 1137Kbps)

http://members.cox.net/enragin_angel...%20quality.avi

I think the quality here is much better than the mpeg-1 version and is still much smaller in size than the mpeg-1 encode by about 30%.

irwin2

>Why what ? Are you making reference to the question about returning to DVD ?

"Techniques and tricks to make hi-quality low bitrate VGA-res MPEG's " -> Why? Betaplayer and xvid is better.

>If you are taking about VGA resolution - yes, you will certainely get something noticeably better with Xvid at 600 Kbps than with MPEG-1 at 600 Kbps, but it will not look good in either case. Blocks will be more blurry than blocky with Xvid, but 600 Kbps is very stressed to code VGA res.

For me is enough. And DVD movies is often widescreen - example 720x384 or 640x352 (because x50v only 640x480 screen 720xXXX not needed) - less pixels then 640x480. On 700mb (for archive) even 2h movies with 60 kbps he-aac with about 730-750kbps xvid 2pass looks really good.


>I've provided the vob to Enragin_Angel, we'll see what he can do at 800 Kbps. I'b be surprised it's better than our sample.

1.7Mbps is 112% more then 800kbps. Yours: "We know that you can gain about 30% in compression using MPEG-4 - not 50%, though" Give mpeg4 a chance.

>Again, the point of this thread is not to discuss the compression efficiency of Xvid vs MPEG-1, it's to show that MPEG-1 can be used very efficiently (some people still think MPEG-1 is only for VCD i.e. QVGA at 1.5 Mbit/sec!!!).

Yes. But still for what? why? 1Gb movie mpeg1 looks worse then 700Mb Xvid. More space and worse quality.
And why in aximsite and x50 general discussions? I think it is for Mutimedia section. And sorry for my simple and poor english

> 1.0 Mbps is only 41% less than 1.7 Mbps... not 70% less!

Correct, but 1.7Mbps is 70% more space usage then 1Mbps :)

PocketTV Team

> K...I did some tests. I'm not sure why you changed the brightness on your encode...It looks like it's noon time in your mpeg encode. That scene was when bruce willis got up in the morning...so it should be dark like mine. Oh yeah, I made no attempt to correct the rainbowing and the dotcrawl that is inherent in both of our encodes.

I wanted the gamma to be more balanced on this demo scene. Sorry.

> Here is the link to an mpeg-1 quality encode at 50% size. (average bitrate 769Kbps)
> http://members.cox.net/xvidcompare/5...%20quality.avi

Thanks. Quality is visibly lower than our demo. I can see lots of block in the fast-moving scenes. Clearly lower quality, but watchable.

> I think the quality is pretty much the same in these two encodes.

No, definitely not. You must compare with http://pockettv.com/mpg/vga/5e-640x480-1.7Mbps-v3.mpg

> Here is a better more decent quality encode. (average bitrate 1137Kbps)
> http://members.cox.net/enragin_angel...%20quality.avi

> I think the quality here is much better than the mpeg-1 version and is still much smaller in size than the mpeg-1 encode by about 30%.

No, I think this one compares with 5e-640x480-1.7Mbps-v3.mpg . I can still see some blocks in this file, in the fast motion scenes, but I would say the quality is about the same, even though there are no blocks visible in 5e-640x480-1.7Mbps-v3.mpg .

So the gain is about 30%, i.e. what was to be expected.

Again, that was not the purpose of this thread, but thanks for confirming that Xvid is about 30% more efficient than MPEG-1.

Enragin_Angel

I'm not sure if you're running post processing or anything, but I can safely say that the decent quality version is a LOT better than your mpeg-1 version. and the encode that is 50% in size is of comparable quality.

In your encode, the scene where she jumps off is laden with dct blocking.
The scene where the police begin to chase shows more blocking on the police car. And specifically at 0:07, you can see that the background scene here is totally blocky as well as the scene right after.

Second opinion anyone?

PocketTV Team

> "Techniques and tricks to make hi-quality low bitrate VGA-res MPEG's " -> Why? Betaplayer and xvid is better.

The purpose of this thread was only to discuss ways to make very high quality MPEG's.

In some cases, MPEG-1 can be prefered, not because it is more efficient, but because it does not involved using technologies with patent royalties.

> even 2h movies with 60 kbps he-aac with about 730-750kbps xvid 2pass looks really good.

I don't think Xvid looks good in VGA at less than 1 Mbps, but it's a question of what you consider good.

> 1.7Mbps is 112% more then 800kbps. Yours: "We know that you can gain about 30% in compression using MPEG-4 - not 50%, though" Give mpeg4 a chance.

Of course, you can invert the way to compute percentage, but when taking about the compression gain of MPEG-4 vs MPEG-1, it goes the other way: a gain of 50% means files are 50% smaller. That has always been the way people have rated the compression gain of MPEG-4 vs MPEG-1. The consensus of the experts is about 30% to 40%. That's true and it's not the point of this thread, but YOU want to change its subject, so fine...

> Yes. But still for what? why? 1Gb movie mpeg1 looks worse then 700Mb Xvid. More space and worse quality.

No, they would look about the same.

> And why in aximsite and x50 general discussions?
> I think it is for Mutimedia section. And sorry for my simple and poor english

Because this thread was specifically avout making VGA resolution MPEG's and the x50v is the only Axim device with a VGA display. But I agree, it should be moved to Multimedia, I have no problem with that.

PocketTV Team

Originally Posted by Enragin_Angel

I'm not sure if you're running post processing or anything, but I can safely say that the decent quality version is a LOT better than your mpeg-1 version. and the encode that is 50% in size is of comparable quality. In your encode, the scene where she jumps off is laden with dct blocking. The scene where the police begin to chase shows more blocking on the police car. And specifically at 0:07, you can see that the background scene here is totally blocky as well as the scene right after. Second opinion anyone?

I looked at both on the desktop using WMP.

I can see absolutely no DCT blocking when she jumps, and no blocking on the police car either in our v3 clip. If you see blocks with one decoder, maybe there is a bug in this decoder... What are you using to compare ?