Help with Understanding the "Padding" in VCDEasy

[Five_by_Five]

Hello. This question is in regards to these notices in VCDEasy when a BIN/CUE is being created:

"mpeg stream will be padded on the fly -- hope that's ok for you! "

and then

"autopadding requires to insert additional 653260 zero bytes into MPEG stream (due to 32663 unaligned packets of 199405 total)"

I know a similiar question has been asked before, but I do need some more details than this provides:

http://forum.vcdhelp.com/viewtopic.php?t=73096&highlight=padding

That post suggested to use TMPGenc MPEG Tools to "remultiplex your MPEG with the setting on "MPEG-1 Video-CD (non-standard)"." But since that topic dealt with not being able to fit that padded MPEG on a disc, that is why they were told to remultiplex the file to get the filesize down. But if you notice above, the amount of the padding that I'm talking about is very small, and will not create a much larger file. So in my case, is it ok to just let VCDEasy "do it's thing" and pad it or not?

So my question is, what exactly is the remultiplex doing to the file? Is it simply doing the same thing that VCDEasy will be doing to it with the padding? I did a test and continued with burning that VCEasy BIN, and then burned the remultiplexed file in Nero. I watched both VCDs on my player, and they seemed to play exactly the same way, no problems with sound or video.

Now if I go ahead and remultiplex a dozen or so files with the same "problem" (not sure if it really is), and do as the other posts suggests and make them a "non-standard VCD", then doesn't that mean I'm not really fixing the problem, that I'm just covering it up? Or is this type of error message, not really an error at all?

Also, does the padding in VCDEasy now make it a VCD compliant? Is that why it is wants to do the padding in the first place? Given this "padding" thing, does that mean there is actually something wrong with my original MPEGs?

Is the padding and/or the remuxing damaging the file in some way?

Lastly, to provide you here with as many details as possible, I remuxed the original first as a VCD standard compliant MPEG, and then as a VCD NON-standard. Here is what VCDxmInfo reports on all 3 files, with filesize noted as well - for some reason, the NON standard got smaller, and the standard one got larger:

~~~~~~~~~~~~~~~~~~
ORIGINAL File - (462,763,940 bytes)

MPEG1, PlayingTime=2658.447s, Bitrate=1411200bps, PtsOffset=0349s, 199405 packets

Video Stream: Motion Video, 352x240, 23.976024fps (FILM), 1150kbps
Audio Stream: Audio Standard MPEG layer2 Stereo, 44100Hz, 229376bps

~~~~~~~~~~~~~~~~~~
REMUX as Standard VCD - (463,380,036 bytes)

MPEG1, PlayingTime=2658.447s, Bitrate=1411200bps, PtsOffset=0348s, 199389 packets

Video Stream: Motion Video, 352x240, 23.976024fps (FILM), 1150kbps
Audio Stream: Audio Standard MPEG layer2 Stereo, 44100Hz, 229376bps

~~~~~~~~~~~~~~~~~~
REMUX as NON-Standard VCD - (462,726,992 bytes)

MPEG1, PlayingTime=2658.447s, Bitrate=1410kbps, PtsOffset=0348s, 199108 packets

Video Stream: Motion Video, 352x240, 23.976024fps (FILM), 1150kbps
Audio Stream: Audio Standard MPEG layer2 Stereo, 44100Hz, 229376bps

~~~~~~~~~~~~~~~~~~

Would appreciate any help, or comments you may have. As I said, it seems that whichever course I take, I don't notice anything difference while playing the discs. So I'm not simply looking for a "do this and your done" answer. I'm hoping to actually learn what is going on here and why. Hopefully, someone here can provide me with the answers to these things so I can actually understand this issue much better.

Thank You Very Much.


5x5

[Five_by_Five]

Forgot to mention that the original, and both remuxed files play perfectly on the PC.

Thanks.


5x5

[Five_by_Five]

Any ideas or comments?


5x5

[vitualis]

Remultiplexing a video file with a multiplexor that KNOWS about VCDs will mean that it will correct the pack size among other things.

The video on a VCD is more than just the MPEG-1 -- it must also be organised in "packs" so that each part fits into on sector on the CD. This is what remultiplexing can do.

The autopadding is basically where the MPEG stream doesn't fit into the packs and so VCDEasy / VCDImager fills up the bits that don't fit with null bytes (zeroes). I personally think that you should simply remultiplex your video with TMPGEnc or bbMPEG first. Autopadding can lead to problems.

If your MPEG video is exactly to spec (in terms of the vidoe bitrate and all that), then with TMPGEnc, mutliplex using the "MPEG-1 Video-CD" setting. The "non-standard" option is for XVCDs.

Regards.

[Five_by_Five]

Thanks for your comments. Earlier, I did go ahead and did another test burn with Nero and VCDEasy. I let VCDEasy do it's autopadding, while Nero didn't tell me anything, but I assume that it did it as well.

Both discs played fine, and I could see no difference. Maybe this is because the padding is such a small amount, or does that matter? I've read on other forums where the padding problem comes out to another 20 megs or more. In my case, it's only 500k on a 500meg file. Do you think the padding amount actually coincides with the amount of playback problems? And if the 500k padding is causing a problem, how could I tell, what would I see or hear?

I think I will take your advice and remux all the files that I need to burn. You seem to believe that doing this is better than letting the autopadding take place, even though I can't see a problem. I was initially concerned that the remux would degrade the files somehow, or create new problems. But if you have the time to answer, please let me know if the amount of autopadding is an issue - more padding=more problems, less padding=less problems? This way, I will know for the future if I run across this again.

By the way, I also read your comments at the vcdimager site, and those were helpful as well.

Thanks.


5x5

[vitualis]

Both discs played fine, and I could see no difference. Maybe this is because the padding is such a small amount, or does that matter? I've read on other forums where the padding problem comes out to another 20 megs or more. In my case, it's only 500k on a 500meg file. Do you think the padding amount actually coincides with the amount of playback problems? And if the 500k padding is causing a problem, how could I tell, what would I see or hear?

Minute amounts of padding are USUALLY okay. For standard VCD MPEG1 streams, the total of the video and audio data yields only a pack size of 2304 bytes per sector. As the MODE2 Form2 sectors used for VCD are 2324 bytes per sector, the stream is supposed to be padded with 20 null bytes per sector (this is what happens when you remultiplex your MPEG).

If your MPEG was almost okay to begin with, the "on-the-fly" padding may accomplish this without the remultiplex.

The ultimate test is in the viewing. If there are problems, it should manifest itself consistenty through the video as little blips or skips.

I think I will take your advice and remux all the files that I need to burn. You seem to believe that doing this is better than letting the autopadding take place, even though I can't see a problem.

The autopadding process is not particularly intellegent (I've had problems in the past) so I prefer to remultiplex my MPEGs. It will depend on you whether you believe it or not to be worthwhile.

If you are making an XVCD, this is where "autopadding" can add significantly to the file size then remultiplexing first is a must.

Regards.