MPEG2 to DV25 field ordering problem

[jayradhart]

Hi all,

I have recently been given some SD MPEG2 files that I need to re-encode into an Avid Media Composer friendly format. I always use Avanti to convert pretty much anything to DV25 so that was the first thing I tried. This did not work because the dominant field of MPEG2 is upper field first but the dominant field of DV25 is lower field first so it looked really screwy! So I tried a basic AVISynth "swapfields" script but this still doesn't solve the problem. It doesn't look as bad but looks very jerky (like it's been film effected) when imported into avid.

I have also tried using Virtualdub and the Reverse Field Dominance filter to move the whole frame up one field but this still produces the jerky effect when imported into Avid. The filed are definitely the right order temporally because I can skip through the footage field by field and it is not jumping back and forward, so I know that is right at least.

Does anyone have any ideas because I'm starting to lose my mind after three days of trying to get this to work?!!!

[minidv2dvd]

why not go with a lossless intermediate? try huffyuv RGBa or yuy2 if you don't need the alpha channel. to go to dv25 entails a lossy recode.

[jayradhart]

Unfortunately they either produce the same jerky result or will not import into Avid, I don't think it's the codec that's the problem but the fact that the footage has been shot upper field first.

Also, there are a LOT of files so wanted to re-encode to a native Avid format that will fast import.

I'm working in a PAL project by the way as well, should probably have mentioned that!

[filmboss80]

I also had similar problems with VirtualDub's internal field swapping filters until I downloaded Scott Elliott's Field Reorder filter. That one worked for me.

You can find it here: http://home.earthlink.net/~tacosalad/video/fldorder.htm

Give it a try.

[Gavino]

I tried a basic AVISynth "swapfields" script but this still doesn't solve the problem.

Try stickboy's JDL_ReverseFieldDominance function from http://avisynth.org/stickboy/jdl-interlace.avsi.

[minidv2dvd]

could you use mediafio in text mode on the mpg and paste the text here?

[jagabo]

Be careful with VirtualDub's handling of interlaced YV12 (4:2:0) sources. It does not handle the chroma channels properly. Get your decoder to output YUY2 (4:2:2) instead of YV12 if possible. Otherwise use AviSynth to convert to YUY2:

WhateverSource("filename.ext") #outputs interlaced YV12
ConvertToYUY2(interlaced=true)

Or, since VirtualDub is going to convert to RGB for filtering anyway:

WhateverSource("filename.ext") #outputs interlaced YV12
ConvertToRGB(interlaced=true)

You can reverse field dominance in VirtualDub by cropping one scanline off the top and then using the resize filter's letterbox option to add one scanline to the bottom.

[jayradhart]

Thanks for all the suggestions guys, I'll give them a try and report back.

Here is the file information from MediaInfo:

General
Complete name : C:\Documents and Settings\edit1\Desktop\body sd.MPG
Format : MPEG-PS
File size : 137 MiB
Duration : 2mn 1s
Overall bit rate : 9 416 Kbps

Video
ID : 224 (0xE0)
Format : MPEG Video
Format version : Version 2
Format profile : Main@Main
Format settings, Matrix : Default
Duration : 2mn 1s
Bit rate mode : Variable
Bit rate : 8 786 Kbps
Nominal bit rate : 9 100 Kbps
Width : 720 pixels
Height : 576 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 fps
Standard : PAL
Colorimetry : 4:2:0
Scan type : Interlaced
Scan order : Top Field First
Bits/(Pixel*Frame) : 0.847
Stream size : 128 MiB (93%)

Audio
ID : 128 (0x80)
Format : AC-3
Format/Info : Audio Coding 3
Duration : 2mn 1s
Bit rate mode : Constant
Bit rate : 256 Kbps
Channel(s) : 2 channels
Channel positions : L R
Sampling rate : 48.0 KHz
Video delay : -80ms
Stream size : 3.72 MiB (3%)

[filmboss80]

Another bit of advice: try the suggestions with just short, 20 second clips that have a lot of motion (video streams only). That should help you find the best solution quickly.

[jayradhart]

I have tried all the suggestions and the best result has come from using AVISynth to Convert the video to YUY2 as jagabo suggested and then use Scott Elliot's short AVISynth script to reorder the fields as filmboss80 suggested. I did not use Virtualdub in the end but put the script into the AVISynth section of Avanti and outputted DV25 so that I can fast import into Avid.

If anyone is interested Scott Elliot's short AVISynth script to reorder the fields is as follows:

AviSource(“sourcefile.avi”) #I used DirectShowSource as I have an MPEG2 file, so DirectShowSource("sourcefile.mpg")
ConvertToYUY2(interlaced=true) #I added this here as described above
AssumeFrameBased
ComplementParity
SeparateFields
Trim(1,0)
Weave

[jagabo]

You can try this too:

DirectShowSource("sourcefile.mpg")
ConvertToYUY2(interlaced=true)
Crop(0,1,-0,-0) #take one scan line off the top
AddBorders(0,0,0,1)#add one scanline to the bottom

The video must be in YUY2 or RGB for this to work. You can't crop or add one scanline in YV12.