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PAC-12 HD TV channel video: 1080i - Printable Version

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PAC-12 HD TV channel video: 1080i - M T - 01-06-2013

I TiVo'ed both the UConn-Stanford WBB game from the ESPNUHD channel and the Stanford-Colorado WBB game from the PAC-12 HD TV channel.  The first was in 720p format; the second, in 1080i.

Until I did this, I hadn't really looked closely at the PAC-12 HD video.  Because it broadcasts sports, I believe I would prefer it in 720p format, with cameras for that format.  I was wondering what the opinion of others was.  If others felt the same way, maybe we could suggest to the PAC-12 to change the format.  Or, maybe someone can educate me and tell me why the PAC-12 format is better.  (This is not in my field of expertise.)

Technical info
1080i single frames are two interlaced fields totalling 1920x1080 pixels, where each field takes a 60th of a second, so a single frame is a 30th of a second.  An image (a "field") is taken, and all the odd-numbered lines are transmitted; then another image (the second field) is taken a 60th of a second later and all the even lines are transmitted.  Together both fields comprise a single frame, which is the composite image with all the odd & even lines combined (interlaced).  The next frame begins 1/30 second later.  If originally captured by a 1080i camera, if something is moving, those fields will show slightly different images and things may look odd.  Also, you are basically updating the picture every 30th of a second.

720p (p="progressive") has a single field in a frame which is 1280x720, where all the pixels are captured and shown at basically the same time.  A new frame is shown every 60th of a second.  All the lines come from a single image.

Why it matters
If you are showing static detail, such as text or a picture of a painting, then 1080i gives you more detail.  Movement isn't an issue.

If you are watching sports, then movement is critical.  The interlace effect can be quite annoying.  Even without the interlace effect, the fact that frames are 1/30 of a second versus 1/60 of a second can mean that you can't quite tell whether the ball arrived first at first base, or who wins a race, or whether a finger touched a volleyball, etc.  With 720p, you can see twice as many consecutive stills of an athlete's technique in a fraction of a second.  I recorded video in HD from the first Olympics with HD broadcast and really enjoyed the 60 frames/second.

It isn't only the participants that are moving.  The camera is moving too, thus causing the same problem for fixed objects (the ground, the spectators).  720p doesn't eliminate blur but it seems more natural to me.

Examples
I can't post full frames as they are too big for attachments.  I'll post
1) a single image with both 720p and 1080i full frame images, scaled to be the same size (as on your TV screen)
2) a cropped, raw 1080i frame (interlaced) and a deinterlaced (ie, a merging of the two fields of a frame) image.  Note how the ball in the first field was to the bottom right, and in the second field had moved to the upper left of the blurry area.  The sorta-solid center area was its overlap in the two fields.
3) a cropped frame from the 720p image.  #2 and #3 are scaled to be the same size as shown on your TV screen (that is, the pixels in the 720p would be 50% bigger in each dimension than the 1080i so either would fully fill the TV screen).


(The 1080i original image was cropped because my computer screen couldn't show it uncropped. The images in #1 are scaled by 50% and are shown with a jpeg quality of 50, in order to meet the restrictions on attachments. Shrinking the 1080i altered much of the interlace effect. The images in #2 and #3 are true size, but shown with a jpeg quality of 75.)



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Ummmm - Redrum - 01-06-2013

Can you repeat the question?

Re: PAC-12 HD TV channel video: 1080i - Farm93 - 01-06-2013

For Sports?
First Choice - 1080P
Second Choice - 720P
Third Choice - 1080i

For Everything Else?
First Choice - 1080P
Second Choice - 720P or 1080i

1080P and 720P you can create your own slow motion reviews of plays while the live feed is watching Chevy Truck commercials.  That is harder with 1080i since the image will often be a touch blurry in slow motion.

Re: PAC-12 HD TV channel video: 1080i - M T - 01-06-2013

1080p isn't in the running as it isn't broadcast, so PAC-12 networks can't use it.  But even so, I would prefer 720p at 60 frames per second over 1080p at 30 frames per second.  With 1080p you get 50% more linear resolution, but with 720p you get double the temporal resolution.

My vote would be for temporal resolution in sports.

(Redrum, if you did miss the question, I was looking for other people's thoughts about whether PAC-12 networks should use 1080i (as they do) or 720p (as ESPNU HD does). )


Re: PAC-12 HD TV channel video: 1080i - Bruce Wang - 01-06-2013

The best HD picture is over the air broadcast because there is no compression.

Re: PAC-12 HD TV channel video: 1080i - jayasena - 01-07-2013

(01-06-2013, 06:37 PM)Publius link Wrote:The best HD picture is over the air broadcast because there is no compression.

Over-the-air is still compressed -- popular video coding formats all have inherent lossy compression. Over-the-air bandwidth isn't as constrained as over satellite or cable, so the degree of compression is usually less, but it's not uncompressed.

Also, I' don't think 1080p60 is in wide use even in OTA broadcasts in the US. It's typically 1080i or 720p. However, the fact that OTA still looks significantly better tells you there's more to this than 720p vs. 1080i (there are lots of knobs that can be dialed in the encoding process without changing the resolution to trade-off video quality vs. the bandwidth consumed). But almost everything else being equal, progressive is better than interlaced for fast motion even if it's at a lower resolution (as is the case with 720p vs. 1080i), modulo the vagaries of video scaling if you are watching on a 1080-line display (TV).

Re: PAC-12 HD TV channel video: 1080i - yvonne - 01-07-2013

http://video.pac-12.com/video/80cWVqNTrBzaC6ZfCZWP11Kzur0aw0Dj

;)