Remove interlace flags from DVD

[STaRGaZeR]

As the title says. Some PAL DVDs are 25FPS progressive, but flagged as interlaced. The goal is to remove those flags and make some nice 25p MKVs with them as backups. I've been searching for a program able to do this but with no success. Any suggestions?

[Guest]

If it is encoded as interlaced, you can't just remove the flags and expect it to suddenly be encoded as progressive!

[STaRGaZeR]

Can you tell me what is it then?:

http://www.megaupload.com/?d=KL16VLN0 (demuxed with DGIndex)

It's not necessary to apply deinterlacing to that source. MeGUI also detects it as progressive, despite the interlace flags.

[Guest]

You have progressive PAL content that has frame structure, and progressive_frame=0 on all frames.

progressive_frame specifies how the frame should be upsampled from YV12 to RGB (strictly, from 4:2:0 to 4:4:4).

Upsampling wrongly can lead to two possible artifacts: 1) DOI (Destruction Of Interlacing, or 2) CUE (Chroma Upsampling Error).

You can assess the result of upsampling by testing these two scripts:

MPEG2Source("VTS_01_3.demuxed.d2v")
converttorgb(interlaced=false) # simulates progressive_frame = 1

...and:

MPEG2Source("VTS_01_3.demuxed.d2v")
converttorgb(interlaced=true) # simulates progressive_frame = 0

In this case, CUE can be seen when upsampled as interlaced, and DOI does not apply because the content is progressive. So you can indeed benefit from upsampling progressively, instead of interlaced as signaled by the stream.

It would be possible to change the flags in this stream, but in general, you have to be careful because it can also affect other flags and how they are interpreted, such as pulldown. But here it could be done.

If you are transcoding, you can just avoid an upconversion to RGB, or, if that cannot be avoided, force the upsampling to be progressive as shown above.

This page has some more information you may find helpful:

http://neuron2.net/autoyuy2/autoyuy2.html

Restream can change the progressive_frame flag. Just open your file, click "Frametype progressive", and then "Write!".

[SeeMoreDigital]

Originally Posted by STaRGaZeR

As the title says. Some PAL DVDs are 25FPS progressive, but flagged as interlaced....

Indeed... This practise was far too common on older PAL DVD's.

What I don't understand is that even newer PAL DVD's, include a "Top Field First" "Picture Coding Extension" and not a "Progressive Sequence" "Sequence Extension": -



Why would this be?

[Guest]

The TFF flag is there in the syntax, so it has to have a value of 0 or 1. It's irrelevant for progressive.

The progressive_sequence flag modifies the interpretation of pulldown flags, and so since there is no pulldown it, too, is irrelevant.

[SeeMoreDigital]

Many thanks for the clarification Donald

[STaRGaZeR]

Interesting info, thanks! I didn't know Restream, that's one hell of a program. Very useful indeed. I've used:

"Frametype progressive" checked because this particular stream has progressive frames, to indicate that chroma upsampling has to be done talking it into account. In the case of an interlaced stream, this should be unchecked for the same reason.

"Progressive sequence" checked, some decoders interpret the stream as interlaced if this is not checked.

Using these options the stream is now perfect.

BTW do you know about any guide explaining MPEG-2 flags for dummies? H.264 would be nice too.

[Guest]

Originally Posted by STaRGaZeR

Interesting info, thanks! I didn't know Restream, that's one hell of a program. Very useful indeed. I've used:

"Frametype progressive" checked because this particular stream has progressive frames, to indicate that chroma upsampling has to be done talking it into account. In the case of an interlaced stream, this should be unchecked for the same reason.

"Progressive sequence" checked, some decoders interpret the stream as interlaced if this is not checked.

Using these options the stream is now perfect.

BTW do you know about any guide explaining MPEG-2 flags for dummies?

You're clearly not a dummy, so I point you here:

http://neuron2.net/library/mpeg2/iso13818-2.pdf

Use the search function giving it the desired flag name:

progressive_frame
progressive_sequence

[STaRGaZeR]

Thanks neuron, questions solved. I'll look for the H.264 specification now

[Guest]

The H.264 spec is also in the library at my site.

[STaRGaZeR]

Yep, reading it right now