Rendering 29.97 NTSC file ==> 1 frame duplicated every 15

philippe44 · Post by **philippe44** » Sat Mar 29, 2008 5:29 pm

Hi - I was using VS 10 for a while and having the following problem : when converting NTSC 29.97 MP4 files (xacti camcorder) the result was (little bit) strobbed, which diminuished a lot the perceived quality (of course, I kept the same frame rate between input and output files).
Using VirtualDub, I discover that in the output file, every 15 frames, two frames where identical (of course this is not the case in the original file), whatever the output compression format was (I was using "custom" to configure the output file). After a lot of trials / errors, I discovered that by configuring a project to be NTSC 29.97 and asking for the output video file to be "same as project settings", this was fixed.
I upgraded to VS11 recently and the problem is still here, but even worse this workaround does not work anymore.
It seems that VS11 is forcing some up/down scaling computing of frame rates and I don't understand why (again input frame rate == output frame rate). ANy help would be welcome

Post by **Ron P.** » Sun Mar 30, 2008 1:45 pm

What are you using for your Project Settings? VS only allows MPEG-1, MPEG-2, VCD or SVCD and AVI with a host of codecs such as DV-Type 1 or 2, MJPEG Compressor, Cinepack, MicroSoft RLE, MicroSoft Video1, and so on.

The project settings are going to play a role in the encoding, so depending on what CODEC you choose will affect the outcome. I've played around with the various AVI codecs for my project settings in a project to convert an mp4 to DVD MPEG-2. So far I have not been able to produce a strobing effect. I did manage to get WinDVD 9+ to lock up, and WMP Classic refuse to play one..

Then you did not state what your output format is?

philippe44 · Post by **philippe44** » Thu Apr 03, 2008 10:52 pm

vidoman wrote:What are you using for your Project Settings? VS only allows MPEG-1, MPEG-2, VCD or SVCD and AVI with a host of codecs such as DV-Type 1 or 2, MJPEG Compressor, Cinepack, MicroSoft RLE, MicroSoft Video1, and so on.

The project settings are going to play a role in the encoding, so depending on what CODEC you choose will affect the outcome. I've played around with the various AVI codecs for my project settings in a project to convert an mp4 to DVD MPEG-2. So far I have not been able to produce a strobing effect. I did manage to get WinDVD 9+ to lock up, and WMP Classic refuse to play one..

Then you did not state what your output format is?

Thanks for your help - Project settings are : AVI [codec = DivX, using 6.8], NTSC 29.97, 24 bits, frame based, 640x480. But I tried AVI uncompressed, lower frame first or upper frame , NTSC 30, PAL, then MPEG2 output, DV output, DVD output etc etc ... no change with VS11. With VS10, all other settings except the first one described [which is the exact native format of the source video - and there is only one video file, always the same] give the "strobbed" result. I can upload you a small clip (40 images) if you want and you will see that in one, there is a frame repeated every 15 and not on the other, the _only_ difference is that one is using VS10 and the other VS11 [and both are using the _same_ project source file and _same_ clip] - it really seems to me that VS11 is _forcing_ some transcoding/resampling which VS10 did not do [unless, in VS10 again the project setting were not the exact source clip format, which took me some time to find out last year]

Philippe

sjj1805 · Post by **sjj1805** » Thu Apr 03, 2008 11:33 pm

Just wandering if it might be something to do with your GOP sequence.
Please view MSP/VS/MF: Encode MPEG's from clips with fast motion

philippe44 · Post by **philippe44** » Sat May 17, 2008 4:22 pm

sjj1805 wrote:Just wandering if it might be something to do with your GOP sequence.
Please view MSP/VS/MF: Encode MPEG's from clips with fast motion

Unfortunately not - the result is exactly the same when using raw uncompressed AVI ...

skier-hughes · Post by **skier-hughes** » Sat May 17, 2008 5:19 pm

Where did you get your raw uncompressed avi file from?
They are very rare and at 65gb per hour very large, so it's very unusual to find them.

philippe44 · Post by **philippe44** » Sat May 17, 2008 5:31 pm

skier-hughes wrote:Where did you get your raw uncompressed avi file from?
They are very rare and at 65gb per hour very large, so it's very unusual to find them.

This is a very small video clip I did with my camcorder. Then I render it in AVI, uncompressed using VS 11+. It is of course BIG, but as the clip is sort, this is not a problem. An a few seconds are enough to see this pattern of "a frame duplicated every 15" (btw, if you see my initial post, I solved this with VS10, but same solution did not work with 11+). I suspect a rendering problem but can't figure it out

philippe44 · Post by **philippe44** » Sat May 17, 2008 9:23 pm

Finally found a workaround (little bit painful but working) :

Use MP4Cam2AVI to have the .MP4 from my camcorder transformed in an AVI container which is then "instructed" to use DivX as a decoder which seems to then "please VS11 (no more the frame repeat problem in rendered files)
Hopefully, MP4Cam2AVI has a batch convert mode for multi-file independant processing and the possiblity to merge many .MP4 into a big .AVI, so I do only one pre-processing with MP4Cam2AVI then I edit in VS11

So it really shows, to my understanding, that the issue is in VS11 decoding engine of .MP4, no ?