Output Display Properties - "Retain Film Mode"

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DB83
Posts: 80
Joined: Wed Feb 01, 2006 12:52 am

Output Display Properties - "Retain Film Mode"

Post by DB83 »

There is a tick box on the above property 'right click on title in list' .

Now I have a source video which was originally an avi at 23.96 fps. I have re-encoded that to :

Mpeg2 - 720*576
24 fps
frame based
8000 kbps
mpeg audio 224 kbps

The properties for this as shown in DVDWS do say 'PAL-DVD'

Now the help page tell me that I should be able to select this property if I have a PAL compliant source at 24 fps progressive to set the flag and there will not be any re-encoding. Unless I miss something, I now have such a source but DVDWS still wants to re-encode.

Confused ???
Devil
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Post by Devil »

I can make only a wild guess. Could it be that the encoder insists on 25 fps for PAL DVD? As I remember it, it does not offer you the choice of 24 fps: if you choose PAL DVD it is 25 fps.
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DB83
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Post by DB83 »

I'll quote the exact wording in the help file :-

"Retain Film mode is only enabled when the active title is in a PAL-compliant format. Selecting this option indicates that the video is in 24 fps progressive scan and will be flagged to 25 fps to comply with PAL specifications. Note that the video's frame rate is not accelerated to 25 fps but only "flagged" as 25 fps."

What I did notice is that 'Convert to Disc Template' option is dimmed out which does suggest that the clip will be re-encoded.

But the question remains that if this clip is not 'PAL DVD Compliant 24fps' then what is.

And surely if it is going to re-encode then I will end up with a 25fps video which is not what I want in this instanstance.
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Post by skier-hughes »

Hve you tried using the file? Does it encode it? As if you don't tick "convert to disc template", if it is a compliant file, it shouldn't touch it.
Devil
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Post by Devil »

OK, It's becoming slightly clearer. The bitstream, which starts about each half-second, contains a sequence header with codes for x and y size codes, aspect ratio code and frame rate code. The latter is a 4-bit code:
24/1.001 - 0001
24 - 0010
25 - 0011 etc...

It would seem that, as 24 fps is not included in the DVD spec, the code is changed to 0011. This means that every sequence header has to be modified, hence the re-encoding. There are a number of other codes that could force it, as well, such as any colour space other than 4:2:0. Thhe problem is that MPEG-2 covers an enormous number of formats but only a very limited sub-set is acceptable for DVD-compliancy. Any one of these can enforce re-encoding if it is in any way non-compliant.
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DB83
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Post by DB83 »

Well, as suggested, I used the file 'as-is' and some form of re-encoding was done.

The properties are now reported as 25fps but the file plays to the same time as previous.

It does not seem to matter now but as this cat is so curious he would like one day to know how you can actually access that tick-box.
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