In SVCD creation, one of the many steps is to "demux" and "remux" the video clip. Why is this so? I capture video via firewire with Ulead Video Studio 4.0 which can output to MPEG 2, do I need to use demux/remux programs? Will the resultant file be SVCD compliant if I use the correct settings, e.g. bit rates, etc.? I don't have svcd creation program to test this right now, and ezcd creator 4 does not support it. Thanks.

-- MJ (sunscream007@hotmail.com), August 08, 2000

Answers

I presently do not use SVCD but from the reading on the net, the MPEG files made for SVCD have special formating. Depending upon the authoring program, you may need to demux/remux. If you use I-Author, you need to demux then remux using I-Author to place the special formating into the stream before I-Author will accept the file and make your SVCD. If you use Nero, then you need to have SVCD compliant file. This can be done my using either the new version of TMPEG or BBMPEG to make the MPEG. If you already have a MPEG2 file 480x480 at 29.97 (NSTC) you can demux, then use BBMPEG SVCD fix to place the spaces in MPEG file for the special formating, the remux the file with BBMPEG to make a SVCD compliant file.

Using I-Author you can also make MPEG1 files (noninterlaced) into SVCD compliant files which I-author will accept and make a SVCD. Some people call this XVCD but it unclear to me that if authored by i- author as SVCD, this is still a MPEG1 SVCD. Using an noncompliant VCD MPEG1 and then having NERO burn it as a VCD (not SVCD) may be a XVCD. From my reading, as along a I Author accepts the MPEG, it will play on any SVCD player however, I am not certain that NERO will always make a 100% compliant SVCD if the MPEG file is not perfect.

-- klebsiella (Klebsiella@visto.com), August 08, 2000.

I have always had trouble understanding why that process is needed or even necessary, its a bit like always de-interlacing, totally unnecceary if the process is developed properly.

You are firewire based and there really is something wrong if you have to emply those tweeks to get a top quality output.

http://aussie01.freeservers.com

for a firewire based VCD & SVCD site.

My site now contains access to sample files in VCD & SVCD where "I put my money where my mouth is" Check it out and see for yourself!

-- Ross McL (rmclennan@esc.net.au), August 08, 2000.

Muxing and De-muxing. First you really don't have to do that at all if your source Mpeg-2 stream IS fully SVCD compliant. That is, that all the (SVCD compliant) internal timing, video and audio pack sizes, header and markers were put into your mpeg-2 when it was captured or authored. Many of us are using "tricks" and techniques to produce SVCD compliant discs with capture boards, or encoders that do not produce a compliant stream for SVCD. If you get the proper bit rates, FPS, and frame sizes correctly, that may not be enough to enable an SVCD authoring program to accept it.

So we "De-mux" the Mpeg-2 "generic" stream into separate video and audio streams. Then we use a "mux" program that has a "proper" SVCD profile to re-combine those streams back into a new Mpeg-2 stream. This Muxing process will put the final audio/video Mpeg-2 stream back together but this time with all the intrinsic items that are need for "book" compliance.

The reasoning for this added step is really simply because we are trying to make a "non-compliant" Mpeg-2 stream into a compliant one.

In my case, I'm looking for a way to utilize my existing (very high quality) analog sources to make SVCD discs. But I don't want to spend hours both capturing to AVI and then encoding to Mpeg-2. My video card will capture directly real time to Mpeg-2. So my total creation time is only a few minutes in addition to the actual capture. The "fixing" of the improper Mpeg-2 with the muxing only takes minutes for hours of video as you are not doing an "encode" or re-compile but just separating and re-combining the audio and video streams. A one hour video takes minutes (don't recall exactly) to complete.

Most of us are using TMPGenc for this de-mux/mux process. The latest version (12) works perfectly for both de-mux and mux but even better yet has another utility added to it's tools that I'm told will fix an out of timing spec MPEG-2 by just parsing the file through it. No more DE-muxing and Re-muxing.

This all came about as more people with existing analog capture equipment became more interested in the higher quality video obtainable with SVCD. Some software encoders, and hardware encoders had the capability to produce Mpeg-2 streams that were "close" but not right on. This can be likened to the early days of VCD creation where some soft/hard encoders had many revisions to their software or firmware until a "truly compliant" VCD stream was able to be produced.

I hope this sort of explains how this whole "muxing" came about. As SVCD becomes more popular, I'm sure you'll see manufacturers paying closer attention to "book" parameters and proper SVCD stream compliance, and in fact providing an SVCD compliant capture/encode option to their products.

A case in point is that pretty nifty Dazzle II hardware encoder. When it first came out it HAD an SVCD profile. But SVCD burning software wouldn't accept it's Mpeg-2 as it was slightly "out of tune". Guys using it would do the "mux" thing and all was well. Within the last few days, Dazzle has just released an upgrade and now their CBR Mpeg-2 SVCD profile is perfect. No more need to "mux". In the meantime, others using methods and equipment not really designed for SVCD are doing the "mux dance".

Hope this helps .. and sorry for the long diatribe.

-- Rich (rich@pcphotovideo.com), August 09, 2000.

Great reply with some real information that tells the background. Once again its non support of the format that creats the whole problem, TMPGEnc needs the highest salutation for build 12, its made life so much easier than ever before and "blown the rest clean out of the water".

From an NLE based viewpoint, all we need now is a timeline plugin for MSP6 and the whole world will be blue!

-- Ross McL (rmclennan@esc.net.au), August 09, 2000.

Thanks guys for your help. I appreciate it.

I did some tests yesterday. I encoded the DV type 1 AVI to SVCD compliant file using TMPEGenc. The output was accepted by Nero. I did not burn it (I was testing at the office), but since Nero accepted it, I assumed it to be fully SVCD compliant. Since Nero didn't have the menuing capability, I thought about using I-Author and then create a disc image to be fed to ezcd creator 4 deluxe. From reading on various posts, I demuxed the already SVCD compliant file, then fed the .mpv and .mpa to the I-Author multiplexer, then the .mps file to the I-Author. But when creating the disc image, I got an error. The error was "MPS ERROR PACKET HEAD!". No image was created. I was wondering how you folks do menus in SVCD. Thanks again.

-- MJ (sunscream007@hotmail.com), August 11, 2000.