please explain SAR/DAR/PAR

[shun]

In particular, what setting should I use for HDV clips when editing in Vegas and saving to x264. When I use the default setting the image becomes 4:3 when it should be 16:9

[poisondeathray]

In mpeg4-avc terminology (which is different than standard historical mpeg2 terminology) , SAR is the sample aspect ratio - but it's called PAR historically or pixel aspect ratio . I'm going to confuse you and introduce another term, FAR or frame aspect ratio which with the w:h of the actual frame dimension . These terms are called different names by different official publications, but the math is the same. That is the bottom line

Display Aspect Ratio = Frame Aspect Ratio x Sample Aspect Ratio
DAR=FARxSAR

16/9 = 1440/1080 x 4/3

Aspect Ratio = (w:h of frame dimensions) x (w:h of pixels)




FYI, Historically in MPEG2 terminology:
DAR = display aspect ratio
SAR = storage aspect ratio (frame size)
PAR = pixel aspect ratio (shape of individual pixels)

Display Aspect Ratio = Storage Aspect Ratio x Pixel Aspect Ratio

Note the confusion here: SAR can be either storage aspect ratio or sample aspect ratio . There is no right or wrong, both governing bodies have used different conventions, although MPEG2 came out first. All the official specs for blu-ray etc. use AVC terminology , so they use Sample Aspect Ratio , not Storage Aspect Ratio. If they stuck with conventional terminology, there would be no confusion



The bottom line is the ratios and math are the same , regardless of what you call the terms

[RabidDog]

Please, PAR, You've gone too FAR, this is really really DAR, after all I am your SAR, stop, or I'll tell MAR

[tb582]

I'm looking to understand this as well, I have a 1280x720 source that I encode to 720x480 as I want to watch it in SD on my PC. I figure encoding it to 720x480 will give my SD encode more pixels to work with rather than going directly to 640x360? This should allow me to set my player to a PAR to 32:27 which will actually playback at 640x360. Am I flawed in my thinking?

[aedipuss]

very, and bizarre to boot. why the heck re-encode 720 to watch it at 480 on a pc. 720 will play it fine, any software will resize it to the monitor.

[jagabo]

I have a 1280x720 source that I encode to 720x480 as I want to watch it in SD on my PC. I figure encoding it to 720x480 will give my SD encode more pixels to work with rather than going directly to 640x360?

It will play it at whatever size it plays it. But the final display aspect ratio will be 16:9. For example, if you have a 1280x960 monitor and play the video full screen, it will be displayed as 1280x720 with letterbox bars top and bottom. If you leave it in a window... Some players will keep the width and resize the height, others will keep the height and resize the width. So your video will play as either ~720x405 or ~853x480. And, of course, most player will let you manually resize the window to whatever size you want. But the player should keep the picture at 16:9 with letterbox bars or pillarbox bars to fill the window.

All that assumes your player is set to keep the aspect ratio. If you have the player set to ignore the aspect ratio it will stretch the video to fit the window or monitor. Or whatever other behavior you have it set to.

[tb582]

Thanks guys, It does sound strange but playback ability aside. I believe since I want to watch it in SD encoding at 720x480 vs 640x360 will result in more pixels thus better quality.

[jagabo]

Thanks guys, It does sound strange but playback ability aside. I believe since I want to watch it in SD encoding at 720x480 vs 640x360 will result in more pixels thus better quality.

Of course. Assuming you use sufficient bitrate.