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    Why 1080 25P is not possible on HDMI out?
    #1
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    Hi everyone, I made a search on this forum and on Google, but I wasn't able to find an answer. I've been wondering for a while why all recent (and not-so-recent) cameras that are able to perfectly record 1920x1080 or 3840x2160 progressive footage at 25 frames in camera, will only output 50i interlaced from the HDMI out.

    I've seen this limitation on EX1R, Z150, Z190, Z280 that my company owns. All those cameras (except the EX1R) can output 1920x1080 25P from the SDI connection.

    It's not a massive problem, but when using HDMI wireless transmitters to a mixer set up on 25P, it all needs to be deinterlaced to 25P.

    To sum it up (on Sony Z150):

    Camera recording in 1920x1080 25P
    - SDI out : 25P
    - HDMI out : 50i - why?

    Camera recording in 1920x1080 50P
    - SDI out : 50P
    - HDMI out : 50P

    Is this a limitation of how the progressive scan is achieved on Sony cameras? Or am I missing a combination of settings that allows me to output 1920x1080 25P from the HDMI? I did take a look at the manual and Doug's video on the Z280 but I wasn't able to find an answer.


    Cheers
    -M
    Last edited by MasterOfWombats; 06-27-2019 at 03:59 AM.


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    #2
    Senior Member
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    I'll probably stand correcting on this as I'm dragging this up from memory. In earlier days, prior to cameras being capable of 50p they were nearly all 50i and monitors were mostly were CRT based. When the first 25p cameras came out CRT monitors could not handle 25 frame progressive output. To get around this the signal was output as PSF (Progressive Segmented Frames) 25p PSF is in fact progressive but each frame is split into two identical half frame segments. This way CRT interlace monitors could accept the signal as they saw the two frame segments as interlaced. True interlace in PAL has a 50th second temporal displacement between fields on movement. The PSF half frames are called segments, not fields, because there is no temporal difference between them. This display method was referred to as PSF (Progressive segmented Frame) recording. The 'gottcha' here was in earlier NLE days NLEs were treating 25p footage as interlace. You had to make sure your project settings were set to 25p and had not defaulted to 50i. By the time 50p had become an established frame rate CRT monitors had all but disappeared and flat panels by in large were all progressive. In other words it is a legacy thing but PSF still exists in the technical specs world.

    Chris Young


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    #3
    Senior Member Cary Knoop's Avatar
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    Location
    Newark CA, USA
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    Quote Originally Posted by MasterOfWombats View Post
    Hi everyone, I made a search on this forum and on Google, but I wasn't able to find an answer. I've been wondering for a while why all recent (and not-so-recent) cameras that are able to perfectly record 1920x1080 or 3840x2160 progressive footage at 25 frames in camera, will only output 50i interlaced from the HDMI out.

    I've seen this limitation on EX1R, Z150, Z190, Z280 that my company owns. All those cameras (except the EX1R) can output 1920x1080 25P from the SDI connection.
    Probably because the decision makers at those companies are all old grey haired men who think that the ye olde TV standard was and is the best thing since sliced bread.


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