[gst-devel] MPEG video format

[Edward Hervey]

On Mon, 2009-03-23 at 20:57 -0700, Dan Taylor wrote:
> I am having a problem with the output video aspect ratio from mpeg2dec.
> 
> A sample that illustrates the problem is available at
> http://www.w6rz.net/parkrun1280_18mbps.ts.,
> although it also happens on live DVB streams.
> 
> The video is supposed to be 1920x1080, but during caps negotiation, it
> is offered as 1280x1080.
> The header appears to have 1280x1080, but aspect code 3, which is 16:9.
> 
> The result is that after scaling the picture appears roughly 5:4, rather
> than 16:9.

   Here I see the following caps: video/x-raw-yuv, format=(fourcc)I420,
width=(int)1280, height=(int)1080, pixel-aspect-ratio=(fraction)3/2,
framerate=(fraction)30000/1001

  Which is:
  pixel_width: 1280
  pixel_height: 1080
  Framerate: 30000/10001
  Pixel aspect ratio (PAR) : 3/2

  The relationship between display-aspect-ratio (DAR) and PAR is as
follows:
  pixel_width / pixel_height * PAR = DAR

  We therefore have DAR = 1280 / 1080 * (3/2) = 16/9

  Everything is correct (a Display Aspect Ratio of 16:9)

     Edward

> 
> Should the mpeg decoder be putting out the 1920x1080 caps, or should the
> other elements of the
> stream be looking at some other caps?
> 
> 
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