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| sternengaenger |
| Posted: Jun 2 2003, 04:16 PM |
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Unregistered
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OK, here is a link to a testclip
testclip on http://130.75.21.166/daten/[/URL]
it is about 47MB in size.
It would be nice if not just anyone is going to download the clip, sinc
the traffic will slow everything down here...
If you load this into Vdub you get an errormessge telling you that
the stream is desynced. That did not happen with the original mpeg.
So i guess it is just from cutting. But the desync ist the same in the real
mpeg.
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| sternengaenger |
| Posted: Jun 2 2003, 04:18 PM |
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Unregistered
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The above link doesn't seem to worke.
Please copy and paste this one into a browser:
http://130.75.21.166/daten/
and choose the testclip |
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| fccHandler |
| Posted: Jun 2 2003, 06:28 PM |
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Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
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@LeQuack and sternengaenger:
Thanks to both of you, you've made a believer out of me. I got both of your test clips and everything you said about them is true. I've been playing with them for a while and I think I'm finally ready to try and put this matter to rest.
From studying the clips, and through many decodings/encodings, it's become apparent to me that their internal video rate doesn't match their audio rate, and it's as simple as that. Unfortunately, I have no idea how they got that way, but I'm guessing that Media Player drops or duplicates frames during playback to keep the timing synchronized.
I tried reencoding the clips with TMPGEnc (as others had suggested) and indeed the output is synchronized. But stepping through the TMPGEnc-produced video and comparing it to the original, it's clear that no frames have been added or deleted, nor has the frame rate changed. However, the audio has been stretched! It was quite visible comparing the original audio and the TMPGEnc-produced audio in Cool Edit's multitrack mode.
I also tried reencoding the clips with FlasK. Again the output was synchronized. But in this case the video frames don't match at all, and many frames have been duplicated compared to the original sequence. The point is, both programs are stretching one stream relative to the other in order to maintain sync.
Conclusion: The plain and simple reason they appear out of sync in VirtualDub is because they really are out of sync internally, and what VirtualDub is showing you is the real deal. In order to correct it, it will be necessary to 1) stretch the audio, or 2) increase the frame rate. I think tweaking the frame rate to 30fps helps a lot with both clips.
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May the FOURCC be with you... |
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| sternengaenger |
| Posted: Jun 2 2003, 06:44 PM |
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Unregistered
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Ok, that is what i thought so fare, too.
I do have the feeling thought, that only stretching the video to the suggested
framerate is at some points not enough.
1. with some Movies it seems that even the if the Framerate is matched with the
suggested new video fps-rate the encoded file seems to be off just a fraction in some points wheras the overall synchonisation seems to matche. I unfortunaly cannot give you a testclip for that. It is just a feeling, but maybe someone can confirm that.
2. Even when choosing the suggested Framerate sometimes it is still out of sync. I think the much better way is the tmpeg way of stretching the audio.
AND it would realy help to have an exact audiostretch possibility. VD 1.5.4 has the audiostretch option, but the precision is not enough, here a precision of
0.9e-6 would be helpfull to even correct a variance of 0.5sec desync on 90min movie. Again I think An automatic calculation and a activationbutten for audio matching to video not vice versa would do a much better job...
And thank you for trying and the confermation.
Besides that I think every streem should be sampled into avi right away.
Why bother with the old mpeg....
jo
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| fccHandler |
| Posted: Jun 2 2003, 07:07 PM |
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Administrator n00b
Group: Moderators
Posts: 3961
Member No.: 280
Joined: 13-September 02
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| QUOTE (sternengaenger @ Jun 2 2003, 02:44 PM) | | I think the much better way is the tmpeg way of stretching the audio. |
This should work: Turn down all of the video settings in TMPGEnc to the crappiest quality so it will do a really fast encode, then rip the audio out of the TMPGEnc-encoded file, and select that as the audio after you open the original MPEG in VirtualDub.
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May the FOURCC be with you... |
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| Pamel |
| Posted: Jun 13 2003, 02:20 PM |
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matroska team member
Group: Moderators
Posts: 151
Member No.: 1353
Joined: 15-December 02
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There is an interesting discussion going on at the Xiph mailling lists about how they are going to be storing video in Ogg. Anyway, they cover this exact same topic and give an interesting reason for it here. I would encourage you to check it out.
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Please take anything I say with many many grains of salt. I can't tell the difference between my AVI and a hole in the ground. |
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