Native DVD and Blu-ray formats: 480i, 480p, 1080p, 16:9, 4:3, 24p, 60i, What the ?

[hydrogin]

I was wondering what kinds of frame rates can be expected to natively reside on a DVD video disc?

I know that 24hz (actually, 24000/1001) should be expected for blu-ray movie discs and that resolutions are typically 1080p or sometimes 1080i for music concerts, etc. But how about DVD? Using Google, I get conflicting answers.

I tried to figure this out using my Panasonic BD85. I inserted a movie DVD (Almost Famous) and using the Picture Information Window as well as the menu of my Panasonic G20 plasma, I was able to determine my default BD85 settings caused a 1080p/60hz to be output (upscaling to 1080p was enabled).

Next, I used the Display button on the BD85's remote to force the output to be 24hz and I confirmed a 1080p/24hz output.

So both 60hz and 24hz could be had from the DVD. But which frame rate was native and which was being "converted"?

I also tried playing a DVD from a TV series (Stargate SG-1) thinking it might natively use the NTSC ~30hz frame rate (not sure if that series was shot on film or video). Both 60hz and 24hz were available so no new information there.

Finally, regardless of what the native DVD resolution really is, I know that TV's typically handle only 24hz or 60 hz inputs. I doubt movies and TV programs are commonly shot with 60hz cameras. So I assume if I see 60hz coming out of my BD85 when playing a DVD, its internally using a 30hz frame rate but outputting at 60hz plus repeating frames for the TV. Did I guess right?

Thanks for any tips, I've always been curious about this.

[MrBoylan]

Blu-rays have a lot more flexibility than DVD. The Blu-ray format features a native 16:9 aspect ratio and resolutions (in North America) of 480i/60, 480p/60, 720p/24, 720p/60, 1080i/60, 1080p/24. Blu-ray 3D discs can be mastered at 720p/60 (frame-packed, MVC codec) or 1080p/24 (frame-packed MVC codec). Most movies are recorded onto film or digital media at 24 FPS (frames per second) and so are mastered on Blu-ray at 1080p/24 in a native 16:9 aspect ratio. Aspect ratios such as 2.4:1 and 2.35:1 (Cinemascope movies) have hard-coded black letterbox bars at the top and bottom of the screen so they do not take full advantage of the 1920x1080 pixel image (but they can still look great on a large screen set or projector).

Some concert films and nature shows, which are shot digitally in 1080p are shot at 30 frames/second. but Blu-ray does not support 1080p/30 so these get mastered onto Blu-ray at 1080i/60, with each half of the 1080p frame split using 2:2 pull down (in other words, no judder is introduced as the 30 FPS signal is evenly split between the interlaced frames). A Blu-ray player will only output this type of source at 1080i/60 (with no de-interlacing) or at 1080p/60 (doubling the frame rate). A good player will detect the underlying 2:2 cadence and output a correct 1080p/60 signal (without trying to do 3:2 pulldown processing). The BD85 handles this type of content fine.

Meanwhile, DVDs are an interlaced (not progressive) format. This was done in order to support the analog/interlaced TV formats that were most popular when DVD was first introduced. DVDs are recorded/mastered at 480i/60 in a 4:3 aspect ratio. Period. (I'll explain the interlaced/progressive thing later). To support widescreen (16:9) movies, an "anamorphic" flag was introduced to the DVD format which basically squeezes a 16:9 image into a 4:3 recording format, then the player (or the TV) stretches it back out to its proper geometry for playback. The benefit to that anamorphic flag is that it allows DVDs to record widescreen movies using the full horizontal and vertical resolution of the DVD format (720x480 pixels in North America), without hard-coding those black letterbox bars into the signal. If you've ever seen a non-anamorphic widescreen DVD ("Amadeus" and "The Abyss SE" come to mind), you'll know how terrible a nonanamorphic widescreen DVD looks once you start blowing it up to fill a large flat panel TV or projection screen (though they seemed fine on my old 32-inch 4:3 Sony XBR CRT back in the day).

As with Blu-ray, cinemascope aspect ratios (2.35:1, 2.4:1, etc.) on DVD do include hard-coded black letterbox bars at the top and bottom of the recorded image, which leads to a less than stellar image if you blow it up for a fixed height Cinemascope-style projection system.

In terms of supporting alternate frame rates on DVD (like 24 frames/second progressive, for movies, example), this is done simply by encoding the 24 frame/second film content using 2:3 pulldown processing to "embed" the 24 frame/second progressive content into that 60 Hz interlaced signal. 30 frame per second material is handled similarly - at 60 Hz but with a 2:2 pulldown. It's up to the player to recognize that cadence and then "extract" the underlying frame rate. Because (unlike Blu-ray) there is no definitive "meta data" in the actual DVD stream to make this a completely fool-proof process, providing a 24p output option for DVDs is a sticky proposition. On your BD85, if you pop in a DVD that was shot at 30 frames/second (2:2 cadence onto 60i disc), then manually put the BD85 into its 24p output mode in the display menu, the motion is going to look really weird and jerky. This is actually why Panasonic makes you set the 24p option for each DVD - this way if the content looks really weird, you'll know why and can set it back to 60 Hz output. For 24p-sourced content, when you set your BD85 to its 24p output mode (on a DVD), the player applies inverse telecine processing to restore the original 24p source material embedded in that 60i stream.

The progressive output of DVD players was something that was added to the format after the first couple of generations of players came out, once displays became available that could take advantage of progressive video signals. But the DVD disc itself is not technically "progressive" as it stores everything in an interlaced format.

These days, there are some Blu-ray players that offer a "source direct" option - this basically sets the player's output to match the native content on the disc itself, in other words, you'll get 480i output for DVD, and usually either 1080i/60 or 1080p/24 for Blu-ray, depending on the encoding on the disc itself. You'd then rely on your TV (or an external outboard video processor or receiver) to convert that signal into the output format that best matches the original source material, and matches the native resolution of your display. But good players like the BD85, the Toshiba BDX2700, the LG BD390 and the OPPO BDP-83 (among others), can be pretty safely relied upon to do a good job of either passing through the content in its native format (where appropriate) or de-interlacing/scaling the content up to either 1080p/60 or 1080p/24 to best match your display device.

I hope that helps!

-CB

[hydrogin]

Bookmarked! This was one of the best posts I've ever seen in an A/V forum. Very educational, thanks!

In terms of supporting alternate frame rates on DVD (like 24 frames/second progressive, for movies, example), this is done simply by encoding the 24 frame/second film content using 2:3 pulldown processing to "embed" the 24 frame/second progressive content into that 60 Hz interlaced signal.

I need to take a harder look at telecining/pulldown as it relates to interlacing/de-interlacing (as opposed to just changing frame rates) .... but does this mean that "judder" should be observable in DVD movies with slow pans if my disc player has 1080p/60 output enabled? Have critical viewers historically complained about this?

It's up to the player to recognize that cadence and then "extract" the underlying frame rate. Because (unlike Blu-ray) there is no definitive "meta data" in the actual DVD stream to make this a completely fool-proof process, providing a 24p output option for DVDs is a sticky proposition. On your BD85, if you pop in a DVD that was shot at 30 frames/second (2:2 cadence onto 60i disc), then manually put the BD85 into its 24p output mode in the display menu, the motion is going to look really weird and jerky. This is actually why Panasonic makes you set the 24p option for each DVD - this way if the content looks really weird, you'll know why and can set it back to 60 Hz output. For 24p-sourced content, when you set your BD85 to its 24p output mode (on a DVD), the player applies inverse telecine processing to restore the original 24p source material embedded in that 60i stream.

Speaking of meta data, my BD85 has an option in the HDMI Connection settings called "Contents Type Flag" (default value is Auto). Is this related to the above, or is this maybe related to HDCP?