Now that you mention it I used my waveform on the Tri-Level sync generator to view the broad pulses on a Tek 1750 a few years back. It was kind of a kludge but I could see how a true progressive Tri Level sync one set of broad pulses per frame. A Psf Tri Level was two sets of broad pulses per frame and a 1080i Tri Level was two sets of broad pulses with twice the number of broad pulses at half the duration judging by the look of things. I perhaps jumped to an incorrect conclusion that the same sync structure carried over to the sync signals in the HDSDI stream. I could not use my analogue scope to see the sync pulses of an SDI stream so I may be miss speaking. I thought I had also looked up the Vertical Sync structure in a Broadcast Engineering book too but I will have to double check.
When I was doing my tests I was trying to check that the Tri Level was locked to house black which I could see by referencing the 1750 to house black and looking for drift when set to external sync. The other thing I was looking for was how monitors know to display the various signal types they are receiving with their on screen displays and how a scope knows the difference between Psf and I. I figured the same differences I saw in the Tri Level sync must occur in the SDI stream which was what allowed the scopes and monitors to determine the type of signal they are receiving. I'm at work now but I will check my book at home to see if I can find it there.
If it's not the sync pulses in the HDSDI stream what is it that identifies the signal type? Perhaps I'm missing the obvious.
--- In Avid-L2@yahoogroups.com, Bogdan Grigorescu <bogdan_grigorescu@...> wrote:
>
> 'In the HDSDI stream the vertical broad pulses for Psf are twice the duration of those for interlace for a total of 5 and in interlace there are 10 broad pulses'
> Any reference to backup this statement John?
>
> To the best of my knowledge the fields and segments are absolutely identical, including the blanking intervals(H and V), as described in the standard: http://read.pudn.com/downloads160/ebook/723748/s274m.pdf
>
> BG
> http://www.finale.tv
>
>
>
> ________________________________
> From: johnrobmoore <bigfish@...>
> To: Avid-L2@yahoogroups.com
> Sent: Saturday, December 7, 2013 6:16 PM
> Subject: [Avid-L2] Re: Is it I or is it P?
>
>
>
>
> When you originally transcoded in the 25P project did you check how Avid had interpreted the field motion of the ama'd clips? Avid does a poor job of properly estimating the field motion. A lot of time it chooses default which isn't always correct. Job is correct that electronically i and psf are basically the same except there is temporal displacement in i media that isn't there in psf media. The difference is in how it is flagged. In the HDSDI stream the vertical broad pulses for Psf are twice the duration of those for interlace for a total of 5 and in interlace there are 10 broad pulses.
>
> I'm wondering if when you ama'd for the original transcode if you manually set the clips field motion to interlace if Avid would then chuck out the second Psf of the frame and double the first. In essence halving the vertical resolution. Similar to motion adapters choosing one field over both field. Worth a try just for the fun of it.
>
> --- In Avid-L2@yahoogroups.com, "Job ter Burg (L2B)" <Job_L2@> wrote:
> >
> >
> > It makes perfect sense.
> >
> > If you have 50i footage and you store it as P, you are in essence folding both fields (1920x540 x2) into a single frame (1920x1080 x1).
> >
> > If you open that footage in a 1080i project, the field stepping command will let you step from one field to the next, where a field is nothing more and nothing less than half of the lines of any frame.
> >
> > Transcoding to P doesn't make it progressive.
> >
> > I or P, both are stored as a frame, but they are flagged differently.
> >
> > J
> >
> > On 7 dec. 2013, at 18:48, Roger <rogershuff@> wrote:
> > >
> > > Came a cross a weird thing (well, maybe not if someone knows the answer). I had a card full of 1080i/50 footage from a Panasonic camera. For a rough edit, I decided to transcode to DNxHD36 (P) to keep the file sizes down. I set the Project format to 1080/25P and transcoded everything I needed. I then happened to examine some of this transcoded footage in a 1080i/50 format project, at full quality. I was able to step through field by field and both fields are still there. This is a dance studio so lots of movement - and I'm not just seeing the nudging up and down of the image that you usually get with progressive footage viewed in an interlaced project. It looks just like interlaced would. Am I mad? Symphony 6.0.4 on Mac OS 10.7.5.
> >
>
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