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Topic: Storing the Aspect Ratio (Read 4913 times) previous topic - next topic
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Storing the Aspect Ratio

What formats support storing the AR? Should it be done in the video stream or in the container? How good is the playback compatibility (Software/hardware players)?

I'm thinking of capturing in 704x576 and storing a"4:3"-tag, but I couldn't find such an option anywhere ChristianHJW said that Matroska supports it, but I would prefer an MP4-solution...

Storing the Aspect Ratio

Reply #1 –
Both MPEG and matroska support AR flags, but these are the only 2 containers i know where AR is stored on the container level.

MPEG4 and RealVideo embed the AR ratio in the video stream itself. To be able to use the AR flag in a MPEG4 video contained in a MP4 container, you have to switch to Linux and use mencoder for encoding and mplayer for playback, or wait for the new 3ivX MPEG4 encoder and MP4 parser .... it should be released pretty soon i heard.

Storing the Aspect Ratio

Reply #2 –
already working solutions (also on windows) are

matroska, with the ffdshow decoder (overlay option ticked)

mp4, with the 3ivx dshow filters
I know, that I know nothing (Socrates)

Storing the Aspect Ratio

Reply #3 –
Quote
I'm thinking of capturing in 704x576 and storing a"4:3"-tag, but I couldn't find such an option anywhere ChristianHJW said that Matroska supports it, but I would prefer an MP4-solution...

You shouldn't capture 704*576. The aspect ratio issues just are so freaky that you should capture 720*576 using a "normal" tv/capture-card which will add some borders around your image and screw up the aspect ratio issues if you use 704*576. You also should set aspect ratio to 128/117 if you use 720*576 resolution if you'll use 704*576 nothing can save you. More information: http://www.uwasa.fi/~f76998/video/conversion/

Storing the Aspect Ratio

Reply #4 –
Latexxx, i get this is all aproximation, but why not capture at 704x576 and add an ar of 391/300 ? (that should be close, if you take that 720x576 is ar 400/300 for example)

edit: but actually if you consider that data on that page is corect then :

On 625/50 systems, only the centermost 702×576 pixels (of 720×576) belong to the actual 4:3 (or anamorphic 16:9) frame.  (so it would be pretty close to use 4:3 for 704x576)

PANIC: CPU 1: Cache Error (unrecoverable - dcache data) Eframe = 0x90000000208cf3b8
NOTICE - cpu 0 didn't dump TLB, may be hung

Storing the Aspect Ratio

Reply #5 –
Actually I was thinking of capturing at any XXXx576 resolution and let the player stretch it to 768x676 or any 4:3 resolution I want. 704 seems particulary interesting, as this is said to be the highest actual resolution that is retrievable from an analogue TV source.

Storing the Aspect Ratio

Reply #6 –
Quote
On 625/50 systems, only the centermost 702×576 pixels (of 720×576) belong to the actual 4:3 (or anamorphic 16:9) frame.  (so it would be pretty close to use 4:3 for 704x576)


But the phucking capture cards digitize the image normally at 720*576 and then resize the picture to 704*576 and you'll end up having smaller active resolution than capturing 720*576.
 

Storing the Aspect Ratio

Reply #7 –
Quote
capture cards digitize the image normally at 720*576 and then resize the picture to 704*576
ic.  (i thought it is about cropping)
PANIC: CPU 1: Cache Error (unrecoverable - dcache data) Eframe = 0x90000000208cf3b8
NOTICE - cpu 0 didn't dump TLB, may be hung