What good are mpeg-1 flicks if they are not VCD compliant??

[jgombos]

I have a Plextor ConvertX tv402u, which has an mpeg-1 encoder. The problem is that the darn thing seems to be producing mpeg-1 files that are not VCD compliant (despite the fact that I tell the capture tool to capture using "mpeg-1/VCD").

Isn't pointless to have non-VCD compliant mpeg-1 files? So when it comes time to author the file, it gets re-rendered, lowering the quality another notch and taking more time in the process, not to mention blowing the content into a larger footprint.

I imagine the only solution to this problem is to not use the Plextor. If no one has a better solution, then I'll let this thread serve to warn potential ConvertX buyers.

BTW- this is a followup to this no longer DivX related thread.

[yoda313]

Hello,



I had something similar with my hauppauge one time I believe. It wasn't producing compatible files if I remember correctly. A simple firmware upgrade solved the problem. Might want to give that a go.

Kevin

[adam]

What are you using to author the file? What error message are you getting? I doubt the mpeg1 is really non-vcd compliant or if it is, its probably just incorrectly multiplexed which doesn't require any reauthoring.

[jgombos]

What are you using to author the file?

I've tried multiple tools, starting with those bundled with the hardware: WinDVD Creator 2, and Ulead Video Studio 8. Then I also tried Nero, since it's mainstream and stable. I have
smart encoding enabled in both Video Studio 8 and Nero, to mitigate re-rendering.

What error message are you getting?

There is no error message. The tools just simply re-render the video, which was MPEG-1 to begin with. Also, the file size increases dramatically when importing the MPG file. ie. I captured an mpeg-1 stream into a file around 670 MB, and the size of the project was measured somewhere between 750 and 800 MB. So the huge increase (which cannot possibly be overhead) must be a result of re-rendering.

I doubt the mpeg1 is really non-vcd compliant or if it is, its probably just incorrectly multiplexed which doesn't require any reauthoring.

I don't really follow you. I assume the video stream coming from the hardware is already multiplexed into an single mpeg-1 stream. But I could be wrong. Is there anything you could suggest?

[adam]

Nero will tell you what it is that is non-compliant about your file before just re-encoding. You must have disabled this option in the settings. I suggest you just look at the actual parameters of your file and decide yourself if there is something wrong. If its 352x240 23.976 or 29.97fps (for NTSC) or 352x288 25fps (for PAL) and encoded at 1150kbits CBR and the audio is 44100kHz, then the streams themselves are compliant. You can see these statistics by importing your mpg into VirtualDubMod and hitting file/file information.

In addition to having compliant streams, they must also be mutliplexed according to the VCD specifications, which require certain things for mux rate, packet size, etc... The fact that the filesize changes so much after re-encoding suggests to me that your mpg is in fact multiplexed incorrectly. Try using TMPGenc's mpeg tools to demultiplex and then remultiplex using the mpeg1 VCD setting.

That was typo in my post earlier. I meant to say that if your mpg is improperly multiplexed it won't require re-encoding, not reauthoring.

[jgombos]

I suggest you just look at the actual parameters of your file and decide yourself if there is something wrong. If its 352x240 23.976 or 29.97fps (for NTSC) or 352x288 25fps (for PAL) and encoded at 1150kbits CBR and the audio is 44100kHz, then the streams themselves are compliant. You can see these statistics by importing your mpg into VirtualDubMod and hitting file/file information.

We might be on to something. I don't have VirtualdubMOD (whatever that is), but I do have Virtualdub 1.5.10, which has the same capability, and everything matched the specs you mention except bitrate. The bitrate on one of these files is reported to average 731 Kbps. This seems to be what is making it non-compliant, and it probably also accounts for the significant size variance. I'm also thinking that because 731 Kbps was listed as an average bitrate, it is probably variable, which is another non-compliance.

In addition to having compliant streams, they must also be mutliplexed according to the VCD specifications, which require certain things for mux rate, packet size, etc... The fact that the filesize changes so much after re-encoding suggests to me that your mpg is in fact multiplexed incorrectly.

Virtualdub reported this when I opened the file:

[!] MPEG: Anachronistic or discontinuous timestamp found in audio stream 0 at 
    byte position 2340, from 0 to 152501. This may indicate an improper join.

[!] MPEG: Anachronistic or discontinuous timestamp found in video stream 0 at 
    byte position 4664, from 0 to 150150. This may indicate an improper join.

Does this indicate that there is also a multiplexing problem?

Try using TMPGenc's mpeg tools to demultiplex and then remultiplex using the mpeg1 VCD setting.

I guess if my bitrate is off, remuxing probably won't help me. I'll probably have to use different hardware if I want to avoid rerendering (since ConvertX does not support frame grabbing).

[jman98]

VCD requires a CONSTANT bit rate of 1115 Kbps on the video. If your average bit rate is 731, yes, this is exactly why it is not compliant and why it is being re-encoded up to 1115 Kbps. This is why your files are growing (higher bit rate after encoding) and going down in quality. Surely you can fix this so you are encoding at the correct settings for VCD. If not, then I guess the Plextor card is not very good at all.

[vcd4ever]

Hi jgombos,

I have been using the VCD format now for 7 years and my experience is that most mpeg's that are not VCD compliant can usually be fixed without re-encoding.

The problem is that there are so many things that can be the reason why a mpeg is not VCD compliant and this makes it very difficult to know if your mpeg can be fixed without re-encoding.

vcd4ever.