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
posted on 2012-01-06 17:03 freshair_cn 阅读(1435) 评论(0) 编辑 收藏 举报