FORUMS: list search recent posts

correctness of MPEG2?

COW Forums : DVD Authoring

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
florin
correctness of MPEG2?
on Sep 19, 2005 at 8:48:36 pm

Is there a simple way to verify that the MPEG2 stream that I'm using to create a DVD is standards-compliant?

Here's the situation:
I am using a Sony DCR-TRV240 digital camcorder. I transfer the Digital8 tapes to the computer using a very simple FireWire utility.
Once on the computer, I transcode the AVI-encapsulated DV stream to MPEG2 (sound is transcoded to AC3). Then I create a DVD file structure which I burn into blanc media. In general, this process works pretty well.
The OS is Linux, the FireWire grabbing utility is called dvgrab, the transcoding is done via transcode (as a decoder from DV to raw YUV, and also handles the audio PCM to AC3 conversion) and mjpegtools (from raw YUV to MPEG2). The DVD structure is created with dvdauthor.

And here's the thing: I am playing the DVDs on my JVC XV-N55 player. Any commercial DVD plays fine on it.
However, some of my DVDs are not played that well. Here's what I told to one of the members of the mjpegtools devel team:

###############################################
When playing the DVD on my player, after 20 ... 40 seconds (not always at the same point in time), there's a change in the way the movie is shown. At the beginning, it's smooth, the motion is displayed in a fluid manner, typical interlaced NTSC. After the change, the motion is displayed in a less fluid manner, very similar to film material converted to interlaced field-based NTSC. It does not stutter per se (that was a wrong description that I used before), there's no discernible pause in video or audio when it transitions, it's just that the video suddenly becomes less fluid (motion-wise) at some point.
Or it's like an entire set of fields is lost (either the odd or the even ones) and the image is rebuilt from the remainder by the player.
Or something like that - I think you have a pretty good idea now. It's the fluid quality of a full chain of interlaced NTSC video that gets lost. After you look at it for like 30 minutes, the brain starts to compensate, but it's still a clear problem to me.
###############################################

I thought maybe there's a spike in the bitrate that hits the player, but no - I am using 7500 kbps max, and the bitrate control is not that bad in the encoder, and the problem still shows up.

The problem is, the mjpegtools devel team has a hard time believing me that it's an issue with their software, and I don't blame them, since I'm the only one reporting the issue to them. OTOH, my DVD player only has issues with material generated by their software, and plus, being a Linux software, their audience is not extremely large. It _could_be_ an obscure bug in their MPEG2 encoder.
It could also be a bug in my DVD player.

So, what I'm asking, I guess, is:
Is there a way to verify the MPEG2 stream for correctness? Maybe some parameter of the stream gets tripped for a brief time and that's enough to push my player over the edge (I've been told that my player is fairly strict w.r.t. the DVD standards specs).
If there's any software that could verify the MPEG2 stream and it's not running on Linux, I would very much prefer to use free software (or at most trial versions); I could boot up Windows to test, but I'd rather not purchase software only to test this thing.

Thank you.

Florin Andrei
http://florin.myip.org/


Return to posts index

John Beale
Re: correctness of MPEG2?
on Sep 22, 2005 at 8:28:56 pm

There are programs out there for MPEG2 and DVD verification, but they range from very expensive to ridiculously expensive. Philips has one which may be the least expensive, for example here:
http://www.licensing.philips.com/services/lover/documents1048.html
http://www.licensing.philips.com/services/lover/h/documents1038.html


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]