In a sensible world there would be a relationship between the frame-size aspect ratio, pixel aspect ratio and display aspect ratio given by
format frame size far par dar NTSC 704x480 22/15 10/11 4/3After doing some research there seem to be some differences of opinion what the pixel aspect ratio is for DV NSTC and D1 NTSC formats. Some sources state that ITU-R BT.601-6 infers a pixel aspect ratio of 10/11 for all these NTSC 480i formats.
format frame size far par dar D1 NTSC 720x486 40/27 10/11 4/3 DV NTSC 720x480 3/2 10/11 4/3In this case the equation far*par=dar doesn't hold exactly for D1 or DV NTSC video. In particular, there are more pixels in the frames of these video formats than needed. Sources that promote the constant value of 10/11 for the pixel aspect ratio state that the reason for these extra pixels is to protect the image from minor pixel shifts that might result from analog technology.
Other sources indicate the pixel aspect ratio is not 10/11 for D1 and DV NTSC formats, but instead takes on the mathematical values so far*par=dar holds exactly for each frame size.
format frame size far par dar D1 NTSC 720x486 40/27 9/10 4/3 DV NTSC 720x480 3/2 8/9 4/3Note that if far*par=dar were to hold exactly for widescreen NTSC video then
format frame size far par dar NTSC 704x480 22/15 40/33 16/9 D1 NTSC 720x486 40/27 6/5 16/9 DV NTSC 720x480 3/2 32/27 16/9
Note that dvgrab was used to download the DV source video and mplayer was used to obtain unscaled 720x480 frames with the command line
$ mplayer -aspect 720:480 -vf screenshot src001.dvFrames obtained using vlc give the same results.
When the camera is held level
width of window pixels in width ---------------- = par * --------------- height of window pixels in heightand when the camera is held tilted
height of window pixels in height ---------------- = par * ---------------- . width of window pixels in widthSetting
width of window lambda = --------------- height of windowand using the pixel measurements obtained from the extracted video frames leads to
lambda = par * 349/347 1/lambda = par * 385/306.These equations have the solution
par = 0.88896.This agrees to more than 3 significant digits with a pixel aspect ratio of 8/9. Therefore, the Canon Elura 90 appears to obey far*par=dar rather than ITU-R BT.601-6.
Repeat the same experiment for the Canon Elura 90 in widescreen mode with image stabilization turned off. The frames are
The equations are
lambda = par * 342/364 1/lambda = par * 302/400which have the solution
par = 1.18731.This agrees to more than three significant digits with the aspect ratio 32/27. The Canon Elura 90 also appears to obey far*par=dar for widescreen.
I repeated the calculations for the Canon Vixia HV30 for HDV source exported as DV through firewire. The computed value for the pixel aspect ratio of the DV footage was 1.18374 which again agrees to more than three significant digits with 32/27.
$ ./make-mpg 720x480.jpg $ ./make-mpg 704x480.jpg $ ./make-mpg 720x480pad.jpgPlaying the first of these video streams using mplayer yields output which contained the lines
Playing 720x480.mpg. VO: [xv] 720x480 => 720x540 Planar YV12This indicates that mplayer plays NSTC video streams with a 720x480 frame size using a pixel aspect ratio 8/9. This is consistent with the camcorder.
Now make a test DVD for determining the pixel aspect ratio of a DVD player. Each video stream needs to be in a separate titleset for dvdauthor to recognize the different resolutions. The dvdauthor configuration file dvd.xml will create a DVD that plays in a loop switching between files. It's an infinite loop, so don't leave it in your DVD player overnight. Author and burn the DVD with the commands
$ dvdauthor -o final -x dvd.xml $ su # growisofs -dvd-compat -dvd-video -speed=1 -Z/dev/dvd final/ # exitThe results from playing the test DVD may be interpreted as follows:
I tested the Toshiba HD-A2 HD-DVD player and the Panasonic DMP-BD70V Blu-ray player. Both players displayed 720x480 video with a 10/11 pixel aspect ratio. The Panasonic player cropped the extra pixels and the Toshiba displayed a slightly wider image by including them.
format frame size far par dar HDV 1440x1080 4/3 4/3 16/9 1080p 1920x1080 16/9 1/1 16/9 720p 1280x720 16/9 1/1 16/9
This means the 720x480 DV source from the Canon Elura 90 in both fullscreen and widescreen modes should be rescaled and encoded as a 704x480 mpeg2 DVD compliant video stream in order to play without image distortion on the Toshiba HD-A2 or the Panasonic DMP-BD70V players. Otherwise, the picture will appear wider by about 2.3 percent.
Many sites on the internet suggest that the pixel aspect ratio of DV source is 10/11 for fullscreen and 40/33 for widescreen. A reliable source supporting this claim is the Sony DVCAM Overview. However, this is not what my measurements show for the camcorders I tested. One reference supporting what I found is at afterdawn.com which stated