Posted: Mon 17 Oct 2005, 2:24 Post subject: Aspect Ratio - Clarification of Anomorphic 16:9 in MPEG2
Being a bit of a video purist I am always trying to get the BEST Quality possible from my video work. My source material format is PAL Anomorphic 16:9 miniDV. I edit using Canopus DVRexM1 hardware (as placed in previous post). Currently I convert to MPEG2 using Canopus's (or is that Canopi) Soft MPEG plug in. I can render with the Aspect ratio flag set on/off.
The standard says that PAL MPEG2 is 720x576 with an aspect ratio of 4:3 or Anomorphic 16:9.
Now using 16:9 Anomorphic WS material as my source if I encode with the aspect ratio flag set to 4:3 then my output file is 4:3 (squished up WS), plays back on my PC DVD player as 4:3 squished up but appears correctly on my Widescreen TV using my DVD player. If I encode with the aspect ratio flag set to 16:9 then the output file appears as a letterbox in 4:3 mode on my PC DVD Player software and normal on a Widescreen TV.
Question. After encoding with the 16:9 flag set, Is the created MPEG2 file a Full frame 4:3 with animorphed 16:9 video or is it a Letterboxed 16:9 video inside a 4:3 frame thereby losing 33% of the quality (due to Top and bottom black letterbox bars)?
In otherwords I am a bit confused as to whether the Aspect ratio flag causes an anomorphed 16:9 source image to be encoded with Letterbox bars, removing the anomorphing and hence with reducing the quality in the final output file.
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Mon 24 Oct 2005, 18:33 Post subject: Re: Aspect Ratio
mnicotra wrote:
Question. After encoding with the 16:9 flag set, Is the created MPEG2 file a Full frame 4:3 with animorphed 16:9 video or is it a Letterboxed 16:9 video inside a 4:3 frame thereby losing 33% of the quality (due to Top and bottom black letterbox bars)?
It should be a full frame 16:9 anamorphic file.
mnicotra wrote:
In otherwords I am a bit confused as to whether the Aspect ratio flag causes an anomorphed 16:9 source image to be encoded with Letterbox bars, removing the anomorphing and hence with reducing the quality in the final output file.
No, the flag is just a flag (it simply tells the player which aspect ratio to use for playback). The fact that it plays in full-screen on your 16:9 TV set (presumably set to "true" 16:9 mode, and not "Zoom") suggests that everything is alright.
Canopus have a history of reporting the wrong resolution and lying about the pixel aspect ratio of their files, though, so, if I were you, I'd still run some tests just to confirm this. When you say:
Quote:
the output file appears as a letterbox in 4:3 mode on my PC DVD Player
That is a bit suspicious. Do you mean that the video window is auto-sized to 4:3? If you resize it vertically, do the bars go away, or does the whole image shrink to keep the bars?
Another way to test if the bars are part of the video is to load the resulting M2V file into PowerDVD and export one frame. If the frame has the letterboxing, then the encoder is faking it. If the frame is 1024x576 or 720x576 with no bars, everything is working as it should.
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