interlaced pc/TV

[pantsdavies]

Hay all, bare with me a mo

retail Pal DVD films are interlaced and play on an interlaced dvd player to a interlaced TV!!!!!(correct?!!!!!))

Pc monitors are progressive, If you play your Retail Pal DVD in the PC dvd reader, Does the Graphics card
Deinterlace the film to play it nice on the progressive Monitor??????

Reason I ask is im messing about hdv camcorder footage and if I convert the footage to interlaced 720 x 576 mpeg2 file, it can look terrible at somepoints, playing on pc monitor.

Why is my interlaced footage bad and retail interlaced dvd's appear perfect playing on pc monitor ??????

the converted footage looks not to bad on dvd player to Pal Tv????????

Cheers

[GMaq]

Hello,
Although I'm not from a PAL Country I think I can answer. The PAL Television Standard dictates that sources need to be 25fps with 625 lines of resolution and "draws" the TV picture using 2 fields. DVD Players take a film source like DVD's Progressive Film 23.98fps and add frames so the DVD will match up with the TV Standard and display properly. When you play a DVD on your computer the playing software and monitor are not bound to the PAL (or NTSC Standard) so many software players play back at the 23.98fps Progressive Film frame rate and thus display properly. Your HDV Camera sources are filmed according to the PAL Standard so will display properly on your TV however having 2 interlaced fields will display on a monitor with interlaced "Comb" artifacts. Clear as mud?

[jagabo]

Retail PAL movie DVDs may be encoded as interlaced or progressive (this is a matter of how the video is handled internally by the MPEG codec) -- but the contents of the frames is almost always progressive. Each video frame represents one film frame. When played by a DVD player to an interlaced PAL TV it sends one field at a time to the TV. When played on a PC both fields are show. But since the contents of the frames are progressive they look fine.

Camcorder footage is pure interlaced video. Each field comes from a different point in time. Pairs of fields are woven together to make frames. So each video frame contains two half-pictures (fields). These are then stored as MPEG in interlaced mode (again this is a matter of how the frames are handled internally by the codec). When these are played an an interlaced TV the DVD player sends (and you see) one field at a time to the TV. But on a computer you see both fields at the same time unless you use a player that deinterlaces for you.

[edDV]

retail Pal DVD films are interlaced and play on an interlaced dvd player to a interlaced TV!!!!!(correct?!!!!!))

Correct. Source video can be full interlace or progressive (film frames or 480p camcorders).

Progressive video can be split and sent to the TV as fields 576i mode or as frames 576p mode.

If an interlace source is sent by the player as 576p, the player must first deinterlace the video. Deinterlace quality depends on the player.

Pc monitors are progressive, If you play your Retail Pal DVD in the PC dvd reader, Does the Graphics card
Deinterlace the film to play it nice on the progressive Monitor??????

The display card (or chipset) will deinterlace by some method all interlace video presented to it. The lazy way is to read 50Hz fields into a frame buffer and read them out as 25Hz progressive frames. This causes lines to separate at the monitor during motion because even and odd lines represent pictures offset in time by 1/25 sec. This method is called a weave deinterlace. A weave gives great quality for a still but results in line split during motion.

Other deinterlace methods can be used (e.g. discard field, blend, bob, average, etc.). Each of those have advantages/disadvantages for still vs. motion video. Advanced deinterlacers analyze the frames for motion and apply different techniques to moving objects vs. nonmoving objects or backgrounds. The result can be progressive video at either 25fps or 50fps. Advanced deinterlacers first determine if the video is true interlace, 25Hz progressive film or NTSC processed film. It will use different methods for each type. The card also needs methods to adapt to different sequences of different types of sources without loosing sync at the transition.

Picture quality depends on the deinterlacer performance. Poor deinterlacers just default to blurring the picture during motion.

Latest PC card deinterlace technologies are "Purevideo" from NVidia or "AVIVO" from ATI. Intel also has different deinterlacer technologies on its various chipsets.

Reason I ask is im messing about hdv camcorder footage and if I convert the footage to interlaced 720 x 576 mpeg2 file, it can look terrible at somepoints, playing on pc monitor.

That is because HDV is 1440x1080i interlace and needs special handling to get from 1080i to 576i without deinterlace. If 576p is the goal, 1080i is first deinterlaced to 1080p and then that is down scaled to 576p. Low end software will deinterlace everything often by cheating. First they drop a field leaving 1440x540p/25fps, then resize to 1024x576p. 576i will be created from the 576p/25fps downscale. The result is jerky motion.

Why is my interlaced footage bad and retail interlaced dvd's appear perfect playing on pc monitor ??????

the converted footage looks not to bad on dvd player to Pal Tv????????

Poor deinterlace and poor scaling causes poor video. A good progressive DVD player or a good HDTV processor will analyze an input video and adapt the process for improved display.

A movie DVD is natively progressive so only needs a weave followed by upscale.

[ntscuser]

retail Pal DVD films are interlaced and play on an interlaced dvd player to a interlaced TV!!!!!(correct?!!!!!))

No, PAL movies are transfered to DVD at 24fps (progressive) and speeded up to 25fps during playback. PAL videos are transferred to DVD at 25fps (interlaced).

[jagabo]

...PAL movies are transfered to DVD at 24fps (progressive) and speeded up to 25fps during playback.

That has not been my experience. Usually 24 fps film is sped up to 25 fps and encoded as 25 fps progressive MPEG on a PAL DVD. Although it's possible to encode at 24 fps and then use pulldown flags to create 50 fields per second for display, I've never seen this done on a commercial DVD. The latter also leaves the video with 2 little jerks every second.

[ntscuser]

...PAL movies are transfered to DVD at 24fps (progressive) and speeded up to 25fps during playback.

That has not been my experience. Usually 24 fps film is sped up to 25 fps and encoded as 25 fps progressive MPEG on a PAL DVD. Although it's possible to encode at 24 fps and then use pulldown flags to create 50 fields per second for display, I've never seen this done on a commercial DVD. The latter also leaves the video with 2 little jerks every second.

From: http://dvddemystified.com/dvdfaq.html#1.19

Video from film is usually encoded at 24 frames/sec but is preformatted for one of the two required display rates. Movies formatted for PAL display are usually sped up by 4% at playback, so the audio must be adjusted accordingly before being encoded.

[Midzuki]

As I said many posts ago, the site dvddemystified-dot-com
does need a serious revision and a general update.

*****

[jagabo]

From: http://dvddemystified.com/dvdfaq.html#1.19

Video from film is usually encoded at 24 frames/sec but is preformatted for one of the two required display rates. Movies formatted for PAL display are usually sped up by 4% at playback, so the audio must be adjusted accordingly before being encoded.

Every film source PAL DVD I have seen was encoded at 25 fps. Rip a VOB file from any commercial PAL DVD and examine it with GSpot or DGIndex. You'll almost certainly see 25 fps.

[manono]

retail Pal DVD films are interlaced and play on an interlaced dvd player to a interlaced TV!!!!!(correct?!!!!!))

No, PAL movies are transfered to DVD at 24fps (progressive) and speeded up to 25fps during playback. PAL videos are transferred to DVD at 25fps (interlaced).

pantsdavies is correct. They've been encoded and stored on the DVD at 25fps (and more often than not encoded as interlaced 25fps - even movies - and always output as interlaced 25fps (or, more accurately, 50 fields per second)). There are no flags set to speed up the video during output.

And for movies, even though they've usually been encoded as interlaced, the source is usually progressive. There's a distinction there.