Picture Aspect Ratio和Pixel Aspect Ratio

1、Picture Aspect Ratio：图像物理尺寸的Width与Height的比例，常见为4：3或16：9；

     Pixel Aspect Ratio：像素点的W：H。在电脑图像中，像素点Pixel是方形的，但视频图像的像素点是矩形的。

2、一些推论

     BT.601的视频，用13.5MHz的时钟采样，每行720个采样点。

     对于NTSC(525-line)，像素比为10：11；

     对于PAL(625-line)，像素比为59：54。

     因此，              

     An image with a standard display aspect ratio of 4:3 (i.e. TV) with 480 lines (i.e. NTSC) would thus have:

• 640 square pixels per line, or
• 704 non-square 10:11 pixels per line

     Note that a 720 pixel scanline has thus captured an extra 8 pixels on either side! A 720x480 frame is not actually a 4:3 image.

     An image with a standard display aspect ratio of 4:3 (i.e. TV) with 576 lines (i.e. PAL) would thus have:

• 768 square pixels per line, or
• 702+54/59 non-square 59:54 pixels per line

     Note that a 720 pixel scanline has thus captured an extra 17+5/59 pixels! (Too bad it doesn't work out to an even 8 per side...) A 720x576 frame is not actually a 4:3 image.

     NTSC、PAL信号，并非所有的采样数据都会被显示出来。

3、各种源的Picture Aspect Ratio和Pixel AspectRatio