i hope this is the right subforum to post this.

this isn't really about recorders; more about a discussion on recording (or capturing).

i'm not sure how the whole process works, but i'm guessing that before 1080i broadcasting, the original stream from the broadcasting company is in full 1080p or some higher resolution..? then it gets split up into even and odd frames, thus making 1080i. then processing at the client's side puts the image back together as best as it can, making a pseudo-1080p image (probably not even good enough to be called "pseudo-1080p"; just 1920x1080).

progressive, to me anyway, means that each frame is a single solid image.

now, there's hardware that can receive and record 1080i broadcasting. if the hardware can record a 1080i stream into 1920x1080, can we then call it 1080p, or at least pseudo-1080p? or will it still be called 1080i?

i know we can get interlaced video, which really sucks. but i'm guessing the capturing hardware will deinterlace it before recording or displaying the image, or it can be done in post-processing; and i know this wouldn't make it a true progressive image.

can you actually record something into 1080i? or is that just something reserved for hardware output?

can someone bridge the gap?

i know we can get interlaced video, which really sucks. but i'm guessing the capturing hardware will deinterlace it before recording or displaying the image, or it can be done in post-processing; and i know this wouldn't make it a true progressive image.Actually, 1080p24 and 1080p30 signals can be sent -- without loss -- as 1080i.

i'm not sure how the whole process works, but i'm guessing that before 1080i broadcasting, the original stream from the broadcasting company is in full 1080p or some higher resolution..? then it gets split up into even and odd frames, thus making 1080i. then processing at the client's side puts the image back together as best as it can, making a pseudo-1080p image (probably not even good enough to be called "pseudo-1080p"; just 1920x1080).Some 24p content is initially distributed as 1080i60 with the flags to repeat the appropriate fields, and then passed on that way by broadcasters and cable companies. Other 24p content is initially distributed as high-bitrate 1080i60 without flags; flags are added -- and repeated fields removed -- with re-encoding for broadcast.

The original 1080p signal can be perfectly reconstructed with inverse telecine. See below:Film-sourced and 1080p24 content

In the case of 1080p24 content -- such as movies and television series -- all this is interpolation is unnecessary. Few people realize that virtually all movies and series content shown on CBS, NBC, HBO, Starz, and Showtime is actually full 1080p, just like Blu-ray and HD-DVD. There is no need to interpolate anything, because the full information for all twenty-four 1080p frames is already there. With 1080p24 content delivered in a 1080i60 signal, you have the following:

Frame1, Field1
Frame1, Field2
Frame1, Field1
Frame2, Field1
Frame2, Field2
Frame3, Field1
Frame3, Field2
Frame3, Field1
Frame4, Field1
Frame4, Field2
Frame5, Field1
Frame5, Field2
Frame5, Field1

This is known as a 3/2 cadence. You have three fields of one frame, two fields of the next, and the cycle repeats.

The fields highlighted in bold are sent using repeat flags, a few bytes which tell the MPEG-2 decoder to repeat a previous field. Only 48 unique fields of information -- each containing half the information in a full 1080p frame -- is typically transmitted every second with 24p content. Compare that to 1080i video, such as sports, where 60 different fields of information is sent every second. For that reason, 1080p24 source content requires less bandwidth to broadcast than video, not more.

The only hardware that has access to those repeat flags is the MPEG decoder inside the STB/DVR or HD-DVD player. Once the MPEG (or VC-1) bitstream from broadcast, cable, or HD-DVD is decoded by the STB, DVR, or HD-DVD player, there are no more flags. All you have at that point is the cadence.

The display processor can't simply combine every two fields, because they don't match up. Instead, the display must reconstruct the original 24 1080p frames through a process known as inverse telecine. Inverse telecine produces an image that is identical to the original 1080p source. To do this, the display processor must determine the cadence of the input signal by comparing the fields. If every field is unique, then the source is video. If every fifth field is a duplicate, then the display processor knows that the source is 24p**; it can eliminate the duplicate fields and reconstruct the original 24p frames. Once this is done, pull-down is applied to repeat the full 1920x1080p frames to match the refresh rate of the display (i.e. 60Hz). At that point, depending on your TV, the image is output directly to the screen, [or] digitally scaled to add overscan, or digitally scaled to fit a lower-resolution panel. On a display that correctly performs inverse telecine, there will be no difference between the 1080i and 1080p output from a Blu-ray player.

Most modern displays can detect the 3/2 cadence on 480p24 content flagged as 480i60 (i.e. DVD), but only a minority can do the same with 1080i60 signals. It is more computationally intensive to do this with high-definition, and many display makers skimp on high-def processing to cut costs. On displays that cannot detect the 3/2 cadence necessary to reconstruct the original 1080p frames, they treat the source as video. They either bob to display the signal as 540p -- as was the case on older/cheaper displays -- or they do motion-adaptive video deinterlace to interpolate the remaining information for the 1080p frame.

Progressive frames created from interlaced content through interpolation will never be as good as material originally acquired in 1080p and reconstructed with inverse telecine. The greatest differences are seen when there is a lot of movement on the screen -- such as horizontal pans -- because the information for that motion exists in a progressive source, but does not exist in an interlaced source.

If you've ever seen combing, blurring, moire, stairstepping, or other interlace artifacts on movies or series content shown on CBS, NBC, TNT, HBO, or SHowtime, chances are it was because your display could not correctly perform inverse-telecine. Unfortunately, most displays do not have quality deinterlace -- of the displays tested by Home Theater Magazine (http://www.hometheatermag.com/hookmeup/1106hook/index.html) (more results here (http://hdguru.com/?p=17)), only seven of the 61 tested would offer the same performance with a 1080i input as they do with a 1080p input. In its latest issue, Home Theater Magazine reviewed and compared (http://www.hometheatermag.com/rearprojectiontvs/207rptvface/) the top 60" 1080p RPTVs from JVC, Mitsubishi, Olevia, Samsung, Sony, and Toshiba. Only two of the six could correctly detect and display 1080p24 content delivered in a 1080i60 transmission, such as Heroes on NBC and CSI on CBS.

Things become a bit more complicated when you have content with "bad edits," as you often get when film and video sources are mixed together. Further, while the actual movie or series may be a 1080p24 source, it's common for commercials to be video sourced. Hence, the display's processing has to be able to switch between video and film modes on the fly, based on what it detects as the source content (60i or 24p). Not all video processors and displays are able to do this well. Some display processors can detect and switch between video and film mode relatively fast (within a few seconds), whereas others may take 30-60 seconds.

** It's not actually quite this simple. Most film-sourced content on cable and broadcast is distributed with the appropriate repeat flags to minimize bandwidth use. But there are times when film-sourced content is distributed and compressed like video. Generally, broadcasters and cable companies like to avoid that, because it wastes bandwidth, but not every broadcast affiliate uses modern encoding equipment.

When content is distributed without those flags and compressed like video, the cadence is still 3/2, but due to compression, every fifth field may not be bit-for-bit identical to a previous field. Hence, to provide reliable inverse telecine, a display processor must not only detect identical repeated fields, but it must also detect when every fifth field is nearly identical. This analysis requires more computational power. Some implementations like the Silicon Optix ReonVX (http://www.siliconoptix.com/contentEngine/dspDocumentDownload.cfm?PCVID=2d4893ca-f663-2e08-c62e-314dbfaf0518) and Realta (http://www.siliconoptix.com/contentEngine/dspDocumentDownload.cfm?PCVID=2d432425-a82d-4ad0-d280-92e6c8f3c801) have the processing power necessary to do this, while other solutions, like those found in Pioneer plasmas, apparently do not.Home Theater Hi Fidelity also posted a more comprehensive article with illustrations below:

High Definition 1080p TV: Why You Should Be Concerned (http://www.hometheaterhifi.com/volume_14_1/feature-article-1080p-3-2007-part-1.html)

but i'm guessing that before 1080i broadcasting, the original stream from the broadcasting company is in full 1080p or some higher resolution..?

No, its most likely already compressed as 1080i mpeg2, and then goes into a decoder/encoder box at the broadcasting station to recompress it into available channel bitrate, and this is what you get out of your TV set.

bfdtv...
that was a good read. it's pretty interesting that hardware can *perfectly* reconstruct the original signal. can it really be considered a perfect 1:1 copy of the original signal? if i capture a 1080i broadcasting, will i get away with saying i have a 1080p capture of a particular show?


timecop...
this is where some of the confusion lies; how can you compress something into 1080i mpeg2? is there such an option in a mpeg conversion program? or, again, is "1080i" something reserved for hardware?

"Program"?
Its just MPEG2@HL, >15<30mbit, with some encoding specifics changed, otherwise its just stadnard MPEG2.

"How do you compress something into that?" Very carefully and expensively (Realtime MPEG2HD capture/encode boards are > $15,000 USD).

I'm not sure I understand the purpose or the question, but it seems neither do you.

well, ok. in the case of encoding something (say home video) into dvd format, it's encoded with the resolution of 720x480 - each frame is a single solid picture with the that resolution. now, after the video has finished encoding and before burning it onto the actual dvd media, is it 480i or 480p?

Depends on the DVDs, I've created homemade DVD out of HDV material (1440x1080i), by dropping half the fields (1440x540), resizing to 720x480 and encoding as 29p w/16:9 flag set.

Again, depends on your source, if you captured from DV or S-Video/etc input into a PC, then the source is already 480i as there are no (cheap) progressive frame capture cards.

"How do you compress something into that?" Very carefully and expensively (Realtime MPEG2HD capture/encode boards are > $15,000 USD).
Some realtime MPEG-2 HD encoders are cheaper than $15K, for professional use, such as these:
$7000 Edirol VC-200HD (http://www.edirol.com/index.php?option=com_content&task=view&id=222&Itemid=424) (without HD-SDI)
$9500 Edirol VC-300HD (http://www.edirol.com/index.php?option=com_content&task=view&id=222&Itemid=424) (with HD-SDI)
$8500 Canopus ADVCHDM1 (http://www.canopus.com/products/ADVCHDM1/index.php) (with HD-SDI)

By the way, the LibraENC encoder chip (http://www.nel-world.com/products/video/products/libraenc/index.html) costs about $60 per chip in volume, according to the press release (http://neasia.nikkeibp.com/dailynewsdetail/005207). Also, HDV camcorders contain MPEG-2 HD encoders, and some cost under $1K (although they don't have inputs for uncompressed HD signals).