iantri
9th October 2004, 17:53
Hello,
I am converting some old 8mm film to NTSC DVD. Unfortunately, the original film is no longer intact, so I am forced to work off of a "professionally" done (in 1991) NTSC VHS transfer.
The transfer exhibits a strange telecine pattern. At first, I thought the film (8mm appearantly runs at 16 or 18fps, depending on who you ask) was just slowed to 15fps and then converted to 30fps with blending and duplication -- it appeared that out of every four fields, two fields were progressive, with the other two being blended. SelectEvery(2,0) works fine for this.
However, I am not so sure now. Strange things happen in the video:
1) The pattern shifts throughout the video -- this seems to happen at the end of each film clip, I assume due to the telecine being started/stopped. Am I correct in understanding MultiDecimate can take care of this?
2) In parts, the video appears to be a series of blended fields however, I still really don't know what is happening, since within the same clip it goes from the above described pattern to this one. Looks like a phase shift or something, but doesn't happen through the entire video..
3) In the "progressive" frames, the video seems ever so slightly 'shifted' horizontally (usually only in the top quarter of the frame) between the two fields that it is composed of. It is usually only noticable in fast motion -- it appears that two frames of film are slightly blended into one field, but only very, very slightly? The result of blending certain frames from the 18fps source to get 15fps?
I wouldn't mind just leaving it interlaced but it is rather difficult to do any noise reduction on it when the (large, excitingly chunky) dirt in one frame of 8mm film is in multiple video fields/frames..
I have posted a sample clip (http://iantri.ath.cx/hvclip.avi) that shows both situations described (it changes in mid-clip in this example). It is encoded as XVID interlaced.
I am converting some old 8mm film to NTSC DVD. Unfortunately, the original film is no longer intact, so I am forced to work off of a "professionally" done (in 1991) NTSC VHS transfer.
The transfer exhibits a strange telecine pattern. At first, I thought the film (8mm appearantly runs at 16 or 18fps, depending on who you ask) was just slowed to 15fps and then converted to 30fps with blending and duplication -- it appeared that out of every four fields, two fields were progressive, with the other two being blended. SelectEvery(2,0) works fine for this.
However, I am not so sure now. Strange things happen in the video:
1) The pattern shifts throughout the video -- this seems to happen at the end of each film clip, I assume due to the telecine being started/stopped. Am I correct in understanding MultiDecimate can take care of this?
2) In parts, the video appears to be a series of blended fields however, I still really don't know what is happening, since within the same clip it goes from the above described pattern to this one. Looks like a phase shift or something, but doesn't happen through the entire video..
3) In the "progressive" frames, the video seems ever so slightly 'shifted' horizontally (usually only in the top quarter of the frame) between the two fields that it is composed of. It is usually only noticable in fast motion -- it appears that two frames of film are slightly blended into one field, but only very, very slightly? The result of blending certain frames from the 18fps source to get 15fps?
I wouldn't mind just leaving it interlaced but it is rather difficult to do any noise reduction on it when the (large, excitingly chunky) dirt in one frame of 8mm film is in multiple video fields/frames..
I have posted a sample clip (http://iantri.ath.cx/hvclip.avi) that shows both situations described (it changes in mid-clip in this example). It is encoded as XVID interlaced.