Mainconcept DVD/mpeg2 average bitrate wierdness

RichMacDonald wrote on 1/14/2002, 10:23 PM

Having rendered a miniDVD with custom bitrates that resulted in a file 25% larger than it should have been, I did a quick test:

VV3.
MainConcept mpeg2 "DVD NTSC" template.
Video Type set to "DVD".
Video Quality set to high.
Max bps = 8e6
30 second avi clip.
Audio bitrate = 224 Kbps
System bitrate set to auto-calculate

Then I altered the average video bitrate as follows:

Expected Actual
Avg bitrate (bps) FileSize (MB) FileSize (MB)
4,200,000 (std) 15.8 16.6
6.300,000 (*1.5) 23.4 30.0
2,100,000 (/2) 8.3 30.0

Now I don't know if I did my calculations correctly:
video MB = (avg bps) *1024 *1024 /8 *30sec = (avg MB/s)
audio MB = (224 Kbps) * 1024 / 8 *30sec = 0.82 MB/s
total MB = video MB + audio MB

For one thing, the 2,100,000 bps run gave exactly the same value as the 6,300,000 bps. I ran this twice with the same result.

For another, increasing the video bitrate by 50% resulted in a file 85% larger.

I'm a newbie, but I'm supposed to be good at math :-)
Can anyone explain what is going on?

Incidentally, I'm keeping "Video Type" at DVD rather than switching to MPEG-2, because VV3 appears to have a memory leak at any non-standard bitrate settings.

Comments

RonC wrote on 1/15/2002, 5:53 PM

In regards to a "memory leak" . I have seen simular issues and even reported it to support. I have not heard anything for about two weeks. It seems that they are kind of ignoring it.

Ron

RichMacDonald wrote on 1/15/2002, 6:49 PM

The "memory leak" problem is also on another thread.
I'm just waiting to see if the late-Jan release of the codec improves things. Hope its soon. . .I have projects filling up my harddisk :-)

RichMacDonald wrote on 1/15/2002, 11:47 PM

I just downloaded the VideoFactory 2.0b release, which contains the MainConcept mpeg3 upgrade. I'm still getting file sizes which make no sense: The 2.1MB/s and 5/3MB/s avg VBRs resulted in the same size file. I didn't repeat the "standard" 4.2 MB/s run, but a similar run (1/3rd the size) indicated this file would be smaller than before. Nothing makes sense right now.

I haven't had time (and my computer is very slow) to run definitive tests. It looks like the out-of-memory error in the MainConcept mpeg3 encoder has been fixed, so I'm going to give that setting a shot overnight. Perhaps something in the "dvd" setting is more specific than in the "mpeg2" setting.

Does anyone know of a good tool to analyze an mpeg2 file and plot the bitrate over time?

stevemil wrote on 1/16/2002, 12:21 AM

I'm seeing weirdness as well. I just starting using the MC encoder yesterday, so I might be doing something wrong. Some better docs would be nice.

I've been using TMpgEnc to convert 130 minute DV movies to 4GB DVD compliant MPEG files with 2-pass VBR. Like you, I've done all the math. With TMpegEnc, I can plug in the average bitrate I want and get out an MPEG file that is almost exactly the size that I intended.

With MC, this is not the case. I entered the same rates (192 Kb/s for audio, 4,155,553 b/s for video) as I do with TMpegEnc and got back an 8GB file. The math just doesn't add up. It almost looks like it is using the maximum rate as the average rate. The max was set to 8,000,000. I notice in the system tab, it says "System bitrate" is 8,192,000. This would produce something near 8GB for 130 minutes. I've also noticed if I change the "Maximum" rate on the video tab, the system rate changes.

I'm doing a constant bitrate encoding now to see if things work differently.

stevemil wrote on 1/16/2002, 12:08 PM

Well, my constant bitrate run keeps hanging at 4%. The program is not responding and is using no CPU.

I was a happy camper with VideoFactory. The only reason I upgraded to Vegas was for the encoder. Seems like that might have been a mistake.

I'll keep playing with it.

RonC wrote on 1/16/2002, 1:50 PM

Check your memeory usage after it hangs. You may find that your locked memory is at you total memory installed. A bug I think.

Ron

RichMacDonald wrote on 1/16/2002, 2:18 PM

Download and install the Videofactory 2.0b.
It also installs the latest MainConcept mppeg encoders,
for VV3.

I made an all-night run with the "mpeg-2" video type and did not crash. Watching the TaskManager tells me that the new version has improved the memory management. Memory still climbds, but it asks for additional memory earlier and does not run out and crash.

Unfortunately, the bitrate settings are still completely useless. I think you're right: it only uses the maximum bitrate and ignores the average setting.
(And it cannot be using 2-pass VBR either, since it encodes as it goes.)

SonyEPM wrote on 1/16/2002, 3:12 PM

We are aware of the bitrate problem and are testing a fix (1/16). The fix will be released with the upcoming Vegas Video 3.0a update (end of Jan +/-).

Jamz wrote on 1/16/2002, 7:30 PM

Was this bit rate problem fixed with Video Factory since if you install the latest update to video factory, it updates the Main Concept encoder in Vegas 3?

stevemil wrote on 1/16/2002, 11:31 PM

I'm running Vegas with VideoFactory 2.0b installed and still have the bitrate problem. Here is a quick repro case...

Load or capture 30 seconds of DV.
Save the clip using the stock "DVD NTSC" template.
I get an MPEG file that is 17,084,416 bytes.
Go back and use the stock template, but change the average rate from the stock "4,200,000" to "4,199,999".
I now get a file that is 31,397,888 bytes.

It appears if you change that rate to anything but the stock value, you get weird results. It looks like if the rate is not the stock rate, then it just uses your max rate.

I'm now ignoring the rates on the video tab and just playing around with the rate on the system tab. I appear to be able to control the file size much better this way, but I'm not totally sure what I am changing. Anyone know if this effects the audio rate, or is just capping the video rate?

One other bug while I'm at it...

11-bit DC always immediately gives me...
"An error occurred while creating the media file test.mpg. The reason for the error could not be determined."

stevemil wrote on 1/16/2002, 11:46 PM

Well, that didn't work. I tried setting both the max and average rate to 8,000,000, the audio to 192, and the system to 4,352,400, and it hangs the app at 6% into my 30 second clip. CPU is at 0%, memory is not the problem.

Sonic - Did you guys actually test this thing before you shipped it (I know MC wrote it, but you guys are collecting the money for it)? I just don't understand how even the most basic functionality doesn't work. Up to now, I've viewed Sonic Foundry as some of the best written and tested software I've ever used. How did this thing ever make it out the door? It just doesn't seem to be up to par with the quality I'm used to from you guys.

Jamz wrote on 1/17/2002, 2:50 AM

Load or capture 30 seconds of DV.
Save the clip using the stock "DVD NTSC" template.
I get an MPEG file that is 17,084,416 bytes.
Go back and use the stock template, but change the average rate from the stock "4,200,000" to "4,199,999".
I now get a file that is 31,397,888 bytes.

I tried that to see if I was having this problem but I didn't get those results. I ended up with a file that was 15.2 MB. I then played with different settings with a 30 second clip. With the settings at 8,000/6,200/4,200 the file was 22.5 MB. I then lowered the average to 4,200 & the file size was reduced to 15.2 MB. It seems like on my system it's going by the average insted of the maximum. However, when the file is played back with Ligo's mpeg player & click on render properties, the bit rate reads the maximum number but when I was using the Ligos plugin with premiere it did the same thing. That's why I was wondering if the bitrate problem was corrected in the Video factory update which updated the Vegas Video encoder. These tests were done using the dvd NTSC template using the video stream setting.

dsanders wrote on 1/17/2002, 8:43 AM

Why can't MC post a detailed and accurate user's guide that steps through all of the settings? This guide should include detailed information on bit management and bit rate calculations. In addition each option should be examined and an explanation should be givin on how it affects the MPEG-2 encoding process. Color snapshots showing various MPEG-2 artifacts and other compression type problems should be included along with an explanation of how to minimize these proplems by tweeking the settings. Complete video examples would go a long way too. These videos could show how the various compression settings affect "Home Movies", "Fast Action Movies", "Still Slideshows", and so on. Finally, an entire chapter should be devoted to creating DVD compliant files.

I realize that most people should just stick to the predefined templates. But hey, I like to play around. Maybe Sonic Foundry could sell it for $29 as a "Tutorial"???

SonyEPM wrote on 1/17/2002, 9:02 AM

We are actively working on fixes for all of the bugs listed here, and should have them resolved in the next week or two. The goal is to have the best MPEG encoder available at any price, so expert-level suggestions to that end are definitely welcome.

We'll continue to watch this thread closely, so thanks for your feedback... and keep posting!

dsanders wrote on 1/17/2002, 12:46 PM

From past forum posts, I have no doubt that Sonic Foundry and MC is committed to producing a "kick butt" encoder.

However when it comes to MPEG encoding, I am finding out that there is a lot of black magic going on during the encoding process. A well thought out tutorial, with samples would really help me.

mayberryman wrote on 1/17/2002, 1:47 PM

I am confident that nearly every poster in this forum would agree. It's not as though VV3 is aimed at the 'toy' market. This is a serious tool...used by many professionals. I for one heartily second the motion for some additional info on the mpeg1/mpeg 2 vcd/svcd/dvd mainconcept encoder settings.

RichMacDonald wrote on 1/17/2002, 11:19 PM

You guys will get it worked out.
IMHO, I don't mind software released with missing features like this. I'd prefer you to get it out then add the features as you can.
The only thing you guys messed up was not posting the problem in a read-me file.
(But I'm a programmer, so I'm not going to point a finger :-)
Please be sure to post to the forum when you release the update. Thanks.

MCTech wrote on 1/18/2002, 11:25 PM

BTW, MainConcept is listening too, and working very closely with SF on the things mentioned here.

The question of documentation is a very good one, and we're not sure what the right approach is. The problem with MPEG is that many of the settings shouldn't be touched, because certain standards (DVD, SVCD, etc.) have very specific parameter ranges.

But instead of hiding some of the more complex settings, SF chose to make them available for the MPEG power users who want to use them.

The templates are designed to provide the best results for most situations, and we are establishing a game plan for possible enhanced documentation.

MainConcept Tech Support

Wondering wrote on 1/21/2002, 11:25 PM

Hi, MCTech

Nice to know you guys are looking into all the problem mentioned.

Just to add, please dun forget that the MPEG1 is also having trouble of the "stuttering audio".

Thanks.

n201cm wrote on 1/24/2002, 8:57 AM

And please, SF, do try to fix the "custon settings" box so that it isn't larger than the screen. My 19" Mitsubishi Diamond Plus 91 monitor (running at 1024x768) will not display the lower portion of the box with the "save" settings unless I run fonts at standard size in my desktop display properties. On a 19" monitor this sure makes for unpleasant reading! Win98SE

Caruso wrote on 2/8/2002, 3:01 AM

'And please, SF, do try to fix the "custon settings" box so that it isn't larger than the screen.'

Thought this problem was something wierd with my system. I set my task bar to auto-hide. When it is hidden, those buttons at the bottom of the custom settings box are available.

Caruso

SonyEPM wrote on 2/8/2002, 9:26 AM

We'll make sure the MPEG custom dialogs fit in 800x600 (should've been that way in the first place)

bigdav160 wrote on 2/8/2002, 10:21 AM

Hi Wondering, I've been doing quite a bit of playing around with the MPEG1 using standard VCD templates and have experienced the stuttering. I do NOT have this problem on a clip encoded with MPEG2 using SVCD template.

I thought the problem might be the buring process so I tried the same file burned with VV3, Nero and MSP's DVD plug-in. ALL have stuttering at the same point (during stills and animations) when played on my DVD player (pioneer 444). What I have noticed is the VCD's will play perfect on my computer with NO stuttering. Again no problems with SVCD's on the DVD player. So I thought maybe it was my media. Burned several brands of CD-r's and CD-RW's all with the same results. Can it be the Pioneer? I wouldn't think so if it plays SVCD's so nicely. If I get a chance, I'll take my VCD over to a store and try it on a few different players. MCTech any insight?