Split Avi to DVD creates Video_Ts folders w. garbled video intro. Help?

[wildgeese]

Hello,

I have a friend who’s leaving the country, and I’m trying to make a dvd copy of "our" movie for him. The movie is fairly long, high quality, and widescreen, and it won’t fit onto one disc. I really don’t want to reduce the quality of the movie. So using ffmpegx to convert to DVD with ffmpeg codec, and jiggering some of the settings to correct for size etc, I’ve split the original avi file into two pieces. When I play those two avis on VLC on my mac, there is no problem with the video quality or audio sync at all.

The problem: when I convert the two avis to DVD and run the resulting Video_Ts files in VLC, about the first 5-10 seconds of each has garbled pixels. Everything else is fine. I’ve tried everything I can think of, searched the forums, etc, including trying to convert the avis using the mpeg2enc codec instead, which created worse problems. I've also raised the bitrate to "best," and even beyond, with no improvement.

Is there anything I’m missing that could eliminate that initial pixel garble, using ffmpegx? Since this is a going-away gift, I'd like it to be perfect, so I’m turning to the experts here once again …. Thanks!

(PS~ Let me know if you need more info? I shortened this posting.)

[Case]

when I run the resulting Video_Ts files in VLC, about the first 5-10 seconds of each has garbled pixels.

Do check to make sure that it isn't VLC being too hasty here. After playback starts, try the Previous button to start at the beginning of the track again. Can it decode the video correctly now?

[wildgeese]

Hi Case,

Thanks as always for replying! I have an image of you in my mind now, especially after choosing the word "hasty." In my mind you resemble Samwise Gamgee!

Unfortunately that suggestion didn't work. I hit the previous button after playback started in VLC, to no effect. Still getting the garbled pixels.

[Case]

Unfortunately that suggestion didn't work. I hit the previous button after playback started in VLC, to no effect. Still getting the garbled pixels.

My suggestion wasn't meant as a solution, but as a test. I've seen VLC start with garbled video sometimes, but that usually picks up after the next I-frame, and isn't rendered like that when hitting Previous. In those cases, I believe the video is fine and the issue is with VLC.

With your file, it seems more serious, and it is likely an encoding error (or an error in decoding the source file before encoding).

I’ve tried [...] to convert the avis using the mpeg2enc codec instead, which created worse problems.

Sorry to hear that. I kinda like mpeg2enc, as it has several useful options that ffmpeg doesn't provide (decode with mplayer; set 3:2 pulldown).

What I would do in this situation:
1/ Get a very short segment of the AVI for test encodings, e.g. a 30 second clip. Short segments would likely show the same symptoms, but you don't have to wait very long for encodings to finish, and see the results.
2/ Install Perian, so that QuickTime understands some extra compression tricks that some files use.
3/ Encode with all five DVD configurations. Hopefully at least one will produce good results for your problem file.
These five configurations are:
a/ DVD ffmpeg preset with 'Decode with QuickTime' (in the Options tab) activated.
b/ DVD ffmpeg preset with 'Decode with QuickTime' de-selected (decode with ffmpeg is used instead).
c/ DVD mpeg2enc preset with 'Decode with QuickTime' activated.
d/ DVD mpeg2enc preset with 'Decode with mplayer' activated.
e/ DVD mpeg2enc preset with both decoders de-selected (decode with ffmpeg is used instead).
Try these test conversions with all other settings at default values, so that we're testing just these options.

If none of these provide a clean image at the start of the converted file, then we'll need to take a closer look at your source file, as ffmpegX may offer little else by itself to prevent your issue.

[wildgeese]

Hi Case,

I am pretty well confused. I did exactly as you suggested. First I downloaded Perian, which apparently I lost when I upgraded to Snow Leopard. I created a couple of small splits and Video_Ts folders from them, default values, with no problem. I was so encouraged I even played around with the values of these to figure out which had the best quality and chose between them, still no trouble.

But when I applied the same rules to the larger split files: garbled intros again. I'm lost.

I'm going to try to go through the errors and see if I can figure anything specific out. Will post back, and thanks again....

[wildgeese]

I don't know if you'll see this message, Case, or if it will do any good. I lost the log, but I don't remember seeing any when the conversion was running anyways. My friend is now long gone. I tried splitting a few other movies and converting them, and their parent movies, but I couldn't reproduce the error. All I know is every time I try converting the larger files I get garbled video in the intro, even if the tests work fine.

I may mail the movie to my friend at this point but he won't be in one place for long, so I'm not sure. If I do, it may be a matter of "living with the mess." If you think there's anything else I can try I'd love to hear it, otherwise thanks for trying!!

~w

[Case]

I don't know if you'll see this message, Case, or if it will do any good.

Hi again, and thanks for the feedback. Still a very puzzling issue you have there.

I lost the log, but I don't remember seeing any when the conversion was running anyways.

I'm not certain that the log would show anything that could hint to a cause for the garbled video, although it may. As I understand it, the conversion continued until the end, so there was no error so severe that the process was stopped.

If you think there's anything else I can try I'd love to hear it, otherwise thanks for trying!!

I could try a few things if I had access to a such a clip that produced the garbled video. But there's not telling if it would help before actually trying. I would like to know what is causing it, though.

My strategy would be to keep trying with different clip lengths and different tools.
Different clip lengths: If 1 one minute clips converts well, does a 5 minute clip work? Does a 15 minute clip work? Does a 45 minute clip work? Does a 75 minute cut work?
Different tools: There are other apps to convert (to DVD). Do they show similar results? Maybe, maybe not.

If you're up to it, you could try converting to an intermediate format first, like DV (lots of disk space needed) or H.264 MP4 (slow conversion). Then check that intermediate file for the same kind of corruption. If such corruption is not present in the intermediate file, then perhaps the conversion to DVD works better from this intermediate format, where the reason for this mess (whatever it is) is already removed?

[wildgeese]

Hi Case,

I just want to post that one of your final suggestions- converting to an intermediate format- did the trick! When I encoded to H264 MP4 the video quality was beautiful but the sound was off; invert mapping produced worse results. (If the audio had worked, I could have fit the whole movie onto one disc, as size was greatly reduced.)

But using DV as the intermediate format worked. It took a long time, as well as a massive amount of space, over 16GB per split, but I had room. The final disc images are smaller, and have excellent video and audio quality. And no messy pixels, yay!

I'm burning it to disc now. Maybe I can mail it to my friend... but I have to find out about postage to Ethiopia!

Thanks again for your expertise!