[Resolved] Making 2 AVIs the same so that VirtualDub can append?

[jagabo]

I found a reference that said that any time you mess with the frames per second (fps), one of the parts that AviFrate can modify, that that often throws the audio/video off sync

Any time you change the frame rate with AviFrate you will end up with audio and video de-synchronization. But if the change is small enough it won't be noticeable. For example, changing from 23976/1000 to 24000/1001 is a 0.0001 percent change, or 3.6 milliseconds over a one hour video. You won't notice that little de-sync between audio and video. On the other hand, changing 25/1 to 24000/1001 is about a 4 percent change, or a difference of about 147 seconds over an hour long video. The A/V de-sync will be obvious.

Note that the frame rate saved in an AVI file is two values, a numerator and a denominator. These correspond the Rate and Scale fields in AviFrate. The FPS rate you see in AviFrate is there just for your convenience. A player uses Rate and Scale to determine the frame rate (FPS = Rate / Scale), or conversely the amount of time each frame should be displayed (time = Scale / Rate).

Unfortunately, AviFrate handles these values poorly. Any time you change one of them it recalculates the FPS field to 3 decimal places, then recalculates the Scale field based on that (possibly) imprecise FPS. For example if you input 1001 in the Scale field then 24000 in the Rate field, AviFrate will generate 23.976 for the FPS field (the actual value should be 23.9760239760239760...). It will then multiply 23.976 by 1001 and change the Rate field to 23999. To get the exact value you want in the Rate field you can enter a slightly higher value in the FPS field -- 23.977 in this case. Save the result right away -- touching any of the fields will cause AviFrate to recalculate the FPS and Rate fields again and generate an incorrect Rate.

[Diana (Cda)]

That explains it, then. That was what was so baffling. When I wrote my initial response here when this supposedly was resolved, I'd just done several dozen AVIs. They all worked perfectly. But when I went on to do more videos, 9 times out of 10 they "failed" with really obvious de-synchronization. In other words, all the workout videos worked just fine with no troubles but they were all pretty much in the same format. I'm guessing the de-synchronization is neglible, as you state. But all the other TV shows and movies, you're right, sometimes the change needed in AviFrate was quite drastic which is why I'm guessing I never had consistent results ever again.

Fortunately for me, though, despite having to "re-encode" to a certain degree, Womble is fast and any loss is neglible to me so that I can get my intro screens out of the static menu items from ripped DVDs without losing quality to any noticeable degree. Since these are all TV rips, I'm okay with the output while having the benefits of XviD over DVD. I have cases of TV recordings that are all going to fit down into a fraction of the number of storage cases! <g>

Thanks.

[Diana (Cda)]

Coming back to this issue again. Hope it's okay to resurrect an old thread.

I use Womble DVD most of the time but it is time-consuming. I'm finding that in a "new" situation, I just need to tack on a synopsis, etc., to an existing AVI. Re-encoding the movie itself is just not feasible. Reluctant to go the AviFrate route again since it had such a high hassle and "fail" rate.

Since enough time has gone by to see if a new freeware has come out to make it so that 2 AVIs can more easily be made so that they can be appended together, thought I'd see if that was the case.

I have much more experience now since I've continued in the year plus since I posted this thread initially to convert DVDs I record to computer AVIs. Yet this issue still is too stupidly difficult unless I need to go the whole route where Womble works perfectly in working with various VOBs.

But "normalizing" 2 AVIs so that I can append together, is there anything out there now that works, anyone know? I'd be making a small intro AVI conform to a larger movie so if there is anything, it should be a snap to use.

Thanks.