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Old 24th September 2015, 20:51   #121  |  Link
wonkey_monkey
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Quote:
Originally Posted by kolak View Post
It does- there are tons of 25p DVDs encoded as 50i.
Aren't they all encoded as 50i?

Or is that just Blu-ray, where 25p isn't even in the spec?
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Old 24th September 2015, 21:05   #122  |  Link
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Does 25p encoded as 50i actually produce a different effect on the screen than would that same content encoded and played at 25p? Since there is no temporal difference between the two fields in a 50i encode that originates from 25p material, part of me thinks that the person viewing the screen would not be able to tell the difference.
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Old 24th September 2015, 21:13   #123  |  Link
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Originally Posted by johnmeyer View Post
Does 25p encoded as 50i actually produce a different effect on the screen than would that same content encoded and played at 25p? Since there is no temporal difference between the two fields in a 50i encode that originates from 25p material, part of me thinks that the person viewing the screen would not be able to tell the difference.
in worst case scenario it is bob deinteralced and this is visible.

nearly all TV have some kind of field matching and will notice that the fields match and it will look the same.

BD and DVD doesn't support 25p only 50i.

you can just treated a 25p/30p stream as interlaced and nothing will happen with it it's just deintelaced and the result from a pretty normal deinterlacer is 50p with 2:2
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Old 24th September 2015, 21:36   #124  |  Link
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Originally Posted by huhn View Post
nearly all TV have some kind of field matching and will notice that the fields match and it will look the same.
Chroma is also encoded (not in the sense of video compression; what's the word I really mean?!) slightly differently for interlaced video, though you wouldn't be able to tell unless you look really closely.
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Old 24th September 2015, 22:09   #125  |  Link
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Quote:
Originally Posted by davidhorman View Post
Aren't they all encoded as 50i?

Or is that just Blu-ray, where 25p isn't even in the spec?
Yes and same for DVD and BD due to lack of 25p support in the spec.

If payer/TV is good enough than you get back original 25p, in other cases it may be treated by player/TV as 50i, which is of course not the best, but not the end of the world neither.
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Old 24th September 2015, 22:11   #126  |  Link
Music Fan
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Originally Posted by davidhorman View Post
Chroma is also encoded (...) slightly differently for interlaced video
Could you develop this point please ?
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Old 24th September 2015, 22:14   #127  |  Link
kolak
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Chroma placement for progressive and interlaced is different, but I never saw this be a problem when watched even on big TV (maybe it actually gets "corrected" by TV filtering system).

Maybe encoders knowing that source is progressive already "correct" it, eg. when x264 encodes as fake interlaced.
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Old 24th September 2015, 22:16   #128  |  Link
Sharc
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Originally Posted by davidhorman View Post
Aren't they all encoded as 50i?
That's what I thought as well, but kolak wrote that they are encoded as 25p and just flagged as interlaced.
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Old 24th September 2015, 22:19   #129  |  Link
kolak
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It depends on the master. If master is originally interlaced than it's encoded as interlaced, but many movies etc are shot at 25p (or 24p and speed up, which also happens in Europe) and these are encoded as fake interlaced.
For the Blu-ray is similar thought I always use to ask for 24p masters. When possible I use to speed up/slow down extras to match main movie fps, so such a disc causes less TV switching, which sometimes is slow and annoying.

Last edited by kolak; 24th September 2015 at 22:23.
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Old 24th September 2015, 22:31   #130  |  Link
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Going back to my earlier question:
Does changefps(60000,1001) applied on a 25p source break the 3:2:3:2:2 pattern? If so, does it cause playback issues say every 1000 frames?
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Old 24th September 2015, 22:35   #131  |  Link
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It depends on how it is played back.
- When IVTC is applied to the 3:2:3:2:2 pattern, playback will be at 30 (29.97) fps with 1 duplicated frame out of 6. So both methods produce the same judder (long frame = 2*short frame duration, happening once every 200ms)
- When bobbing is applied to the 3:2:3:2:2 pattern the judder amplitude is lower (long frame = 1.5 * short frame, but the change happens 3 times within 200ms), which I feel is smoother to watch.
Interesting, it probably depends on players.

There is another solution quickly mentioned on 1st or 2nd page : DGPulldown (if the encoding is for dvd).
I believe it allows to encode 25p and play it at 29.97 fps without speed change, thanks to a flag.
The main advantage is that the bitrate is higher by frame (compared to 30p or 60i), because there are less frames to encode by second (the maximal bitrate allowed on dvd is always the same, whatever the framerate).
Other advantage : the encoding is simpler, there is nothing to do with Avisynth about framerate.
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Old 24th September 2015, 22:43   #132  |  Link
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Yes, but as I said- this is mainly for broadcast transmission.

Saying this- they could do this on the headers level themselves during last stage before transmission
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Old 24th September 2015, 22:43   #133  |  Link
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DGPulldown is found here:
http://rationalqm.us/dgpulldown/dgpulldown.html

As I understand it uses soft-pulldown based on flags and timecode, as opposed to hard-pulldown produced by changefps().
DGPulldown hence preserves the original video.
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Old 24th September 2015, 22:50   #134  |  Link
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Yes, but this is strictly for mpeg2. What if I need to deliver AVC-I (which is now becoming new standard) file as master or HDCAM tape ?

Last edited by kolak; 24th September 2015 at 23:13.
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Old 24th September 2015, 22:57   #135  |  Link
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Right, for mpeg-2 only. But I thought from your original post that's what you need.
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Old 24th September 2015, 23:34   #136  |  Link
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Originally Posted by Music Fan View Post
Interesting, it probably depends on players.

There is another solution quickly mentioned on 1st or 2nd page : DGPulldown (if the encoding is for dvd).
I believe it allows to encode 25p and play it at 29.97 fps without speed change, thanks to a flag.
The main advantage is that the bitrate is higher by frame (compared to 30p or 60i), because there are less frames to encode by second (the maximal bitrate allowed on dvd is always the same, whatever the framerate).
Other advantage : the encoding is simpler, there is nothing to do with Avisynth about framerate.
I should add that correct IVTC will include decimation, as mentioned by vivian. Means playback will be restored at the original rate, means no duplicated frames = no judder.
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Old 25th September 2015, 08:19   #137  |  Link
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I should add that correct IVTC will include decimation, as mentioned by vivian. Means playback will be restored at the original rate, means no duplicated frames = no judder.
This also means a Ntsc dvd would be displayed in 50 hz, that's strange.
The DGpulldown trick allows to encode in 25p with the mpeg-2 encoder, but as the framerate for the player is 29.97 fps (thanks to DGpulldown's flag), the resolution has to be 720*480, not 720*576.
But it's maybe possible if player's resolution is set on 1080p. Because if it's set on 480p, I don't believe the player will be able to send 480p with a 25p (or 50p actually) framerate.


edit : actually I believe that the mpeg-2 encoder needs the final framerate (29.97 in this case), thus it has to be fed with 720*480 @ 29.97 fps, not 25 (unless the encoder accepts to encode 720*480 @ 25 fps). But don't use changefps() in avs script to convert 25p in 29.97, use assumefps(30000, 1001), but not for the sound which will keep its 25p speed.
DGpulldown's flag will change it (as if assumefps(25) was done) and will add the 29.97 fps flag.
It also means the encoding bitrate can be higher than 10 Mbps because of the slowdown made by DGpulldown : 11,5 Mbps @ 29.97 fps means 9,59 Mbps when slowed down @ 25 fps.

Last edited by Music Fan; 25th September 2015 at 09:07.
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Old 25th September 2015, 08:24   #138  |  Link
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Originally Posted by Sharc View Post
Going back to my earlier question:
Does changefps(60000,1001) applied on a 25p source break the 3:2:3:2:2 pattern? If so, does it cause playback issues say every 1000 frames?
I would say yes, but make a test and look around the 1000th frame and compare with changefps(60) to be sure.
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Old 25th September 2015, 10:18   #139  |  Link
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I would say yes, but make a test and look around the 1000th frame and compare with changefps(60) to be sure.
ChangeFPS(60000,1001) breaks the cyclic pattern of the fields, like
...3:2:3:2:2:3:2:3:2:2:3:2:2:3:2:3:2:2:3:2:3:2:2......

or in case of ChangeFPS(30000,1001) the frame pattern becomes
....2:1:1:1:1:2:1:1:1:1:1:2:1:1:1:1:2:1:1:1:1 .....

I don't know if and how these hickups affect the playback, I didn't test on player + TV.

It is definitely better to do the pulldown with ChangeFPS(60) or ChangeFPS(30) respectively, and add the slight slowdown AssumeFPS(...) for standards compliance at the end of the script. But kolak wrote that he does not want any speed change, if I remember correctly.
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Old 25th September 2015, 10:58   #140  |  Link
manono
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This also means a Ntsc dvd would be displayed in 50 hz...
No it doesn't. It'll be output by the DVD player at 59.94 fields per second, just like any other NTSC DVD.
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I don't believe the player will be able to send 480p with a 25p (or 50p actually) framerate.
It doesn't. It sends 59.94 fields per second, just as any other NTSC DVD.
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actually I believe that the mpeg-2 encoder needs the final framerate (29.97 in this case), thus it has to be fed with 720*480 @ 29.97 fps,
No, it can encode at a number of progressive framerates, including 25fps. I've encoded 720x480@25fps many times. And even if your own MPEG-2 encoder doesn't allow it for one reason or another, you can make it come out alright in the end by a proper use of DGPulldown.
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It also means the encoding bitrate can be higher than 10 Mbps
If you encode at 25fps, you use the 'normal' bitrate settings. Yes, if you encode at some other framerate with the intent of changing it afterwards when using DGPulldown then, yes, you can 'adjust' the bitrates. For example, if you want to encode as progressive a silent film at 19.98fps, you can't because 19.98 isn't allowed by an MPEG-2 encoder. You encode at 23.976fps and adjust all the bitrates upwards by 20% (23.976/19.98=1.2). Then when done get the framerate correct again by applying DGPulldown set for 19.98->29.97. I don't know why, though, you'd want to encode a 25fps source at 29.97fps when you can just as easily encode for 25fps, at least when using the MPEG-2 encoders with which I'm familiar (CCE and HCEnc).

Last edited by manono; 25th September 2015 at 11:01.
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