Scenalyzer captures wrong field order, how to reverse fields.

[SF01]

I have noticed many times that scenalyzer will randomly ssign fields to frames when the input is analog video converted to DV.

The clearest example is when two scenes are joined together, the result is a frame with a set of fields from the previous scene and the other field is from the next one.
So instead of having frame composed of fields 1 and 2, the frames are 2 and 3, 4 and 5, etc.

Is there a quick way to reverse the field assigned to each frame? DV is intraframe compression, so shouldn't cause transcoding.

[jagabo]

The only way to fix it is to convert to TFF -- but then it can't be DV.

[Skiller]

I'm pretty certain it is not Scenalyzer phase shifting the fields but whatever capture device you are using does it. Well, it's not even "wrong" per se. It's analog video. It's a stream of fields.

In DV compression the fields are stored within frames, so unfortunately they cannot be rearranged without re-encoding.

But why bother? Phase shifted fields are not an issue, just a slight nuisance.

[SF01]

I'm pretty certain it is not Scenalyzer phase shifting the fields but whatever capture device you are using does it. Well, it's not even "wrong" per se. It's analog video. It's a stream of fields.

In DV compression the fields are stored within frames, so unfortunately they cannot be rearranged without re-encoding.

But why bother? Phase shifted fields are not an issue, just a slight nuisance.

Yes, it's the device that is receiving the video signal, I'm just capturing with Scenalyzer.
It is a nuisance and I'm perfectionist. But apparently not enough to recapture.

I guess it can be closed now.

[Skiller]

But apparently not enough to recapture.

Which may not fix it anyways.


Aren't you going to do any kind of processing and encoding to a more watch-friendly format? Because if you do, while at it, all it would take to phase shift the fields again and thus re-pairing them is:

SeparateFields()
Trim(1,0)
Weave()
#Field order is reversed as a side-effect, so is now TFF

[Alwyn]

Yes, it's the device that is receiving the video signal

Out of interest, what is it? A camera? ADVC?

[SF01]

But apparently not enough to recapture.

Which may not fix it anyways.


Aren't you going to do any kind of processing and encoding to a more watch-friendly format? Because if you do, while at it, all it would take to phase shift the fields again and thus re-pairing them is:

SeparateFields()
Trim(1,0)
Weave()
#Field order is reversed as a side-effect, so is now TFF

I convert only at the request, how do I incorporate it into ffmpeg command?

Yes, it's the device that is receiving the video signal

Out of interest, what is it? A camera? ADVC?

It depends, I use DCR-TRV828E, DSR-2000AP, or HVR-M15AE.

[poisondeathray]

For ffmpeg equivalent command would be like this

-vf setfield=tff,separatefields,trim=start_frame=1,weave,setfield=bff

[SF01]

For ffmpeg equivalent command would be like this

-vf setfield=tff,separatefields,trim=start_frame=1,weave,setfield=bff

Thanks.

The code I am using no is:

for %A in ("*.*") do ffmpeg -i "%A" -c:v libx264 -profile:v main -crf 16 -filter:v "crop=702:576:9:0,scale=768:576,setsar=1" -c:a aac -b:a 384k "F:\%~nA.mp4"

[jagabo]

Another way to reverse field order is to shift the frame up or down by one (or any other odd number) scan line. That won't "fix" your issue at scene changes but it keeps you from losing a field at the start and end of a clip.

Crop(0,1,0,0).AddBorders(0,0,0,1) # crop one line off the top, add one to the bottom, ie, shift the frame up by one scan line

Subsampled chroma restrictions apply.

[poisondeathray]

For ffmpeg equivalent command would be like this

-vf setfield=tff,separatefields,trim=start_frame=1,weave,setfield=bff

Thanks.

The code I am using no is:

for %A in ("*.*") do ffmpeg -i "%A" -c:v libx264 -profile:v main -crf 16 -filter:v "crop=702:576:9:0,scale=768:576,setsar=1" -c:a aac -b:a 384k "F:\%~nA.mp4"

You can just add it to the filter chain.

-filter:v "setfield=tff,separatefields,trim=start_frame=1,weave,setfield=bff,crop=702:576:9:0,scale=768:576,setsar=1"

Don't forget to encode and flag interlaced for libx264 , otherwise it will be encoded and flagged progressive

x264opts bff=1