PAL DVD video is 1024 x 576 - wrong resolution?

[draig-llofrudd]

Hi,

I have a video from a DVD (not Blu-ray), and it has the resolution 1024 x 576. Is this not the real resolution? I heard that actual PAL rips are always up to maximum 720 x 576. I guess the person has re-encoded it? And if it natively is 720 x 576, I guess, assuming the screen isn't stretched, there would be black bars above and below the video, is this right?

[jagabo]

PAL DVD is always 720x576* with either a 4:3 or 16:9 display aspect ratio (DAR). Either the player or TV will adjust for the DAR at playback. If the DVD is 16:9 DAR the the 720x576 frame is stretched horizontally to a ratio of 1024x576. If it's 4:3 DAR the frame is stretched to a ratio of 768x576. Whether black bars are added depends on the shape of the display. If the DAR of the DVD doesn't match the aspect ratio of the screen lettebox or pillarbox bars will be added. For example to display a 4:3 DAR DVD on a 1920x1080 (16:9) display, the 720x576 frame is upscaled to 1440x1080 (4:3) and 240 pixel wide pillarbox bars are added to the left and right. 240+1440+240 = 1920. On the other hand, a 16:9 DAR DVD is simply upscaled to 1920x1080 because the DAR of the DVD matches the AR of the screen.

* Actually, a few other frame sizes are legal: 704x576, 352x576, 352x288. But those are rarely used.

[hello_hello]

I have a video from a DVD (not Blu-ray), and it has the resolution 1024 x 576. Is this not the real resolution?

The display aspect ratio can be different to the resolution (storage aspect ratio). When encoding a PAL DVD you can resize it to the correct display aspect ratio and encode it that way (ie 1024x576 for a 16:9 DVD) or you can encode it at the original resolution (ie 720x576) and leave it up to the player to resize it correctly on playback as it would for the original DVD. Assuming the player supports doing so for video in MP4s or MKVs etc.

If you use the first method, you can resize the video to any 16:9 dimensions for encoding. Back in the days of standard definition AVIs, the maximum width was 720 so dimensions such as 720x404 were often used. There's no 720 width limit for HD players though, and resizing the width to 1024 for 1024x576 will probably retain more detail than reducing the height instead (720x404).

For the second method, you could think of the player resizing the video from 720x576 to 1024x576 on playback, then upscaling it from there to fill a 16:9 screen, although it'd be all done in one step.

[draig-llofrudd]

I know that there is a set up aspect ratio in the MPEG header, but in my specific file the true resolution is 1024x576, not the playback resolution. I would like to stretch it back to 720x576 since I know that it is the original resolution. But yes, I'm wrong about the black borders. Thank you for that.

The stretch-back is my turn now. ^^

But does it mean, that videos are all recorded too narrow and just reproduced broadly? I've checked some normally looking 720x576 videos which get displayed by 1024x576. My conclusion is, that when it would be displayed in it's native resolutin, the video would look very weird.

[sneaker]

DVDs are ALWAYS anamorphic. They are supposed to be stretched on playback, never with 1:1 AR in what you called "original resolution".

[JVRaines]

PAL DVD is always 720x576* with either a 4:3 or 16:9 display aspect ratio (DAR). Either the player or TV will adjust for the DAR at playback. If the DVD is 16:9 DAR the the 720x576 frame is stretched horizontally to a ratio of 1024x576. If it's 4:3 DAR the frame is stretched to a ratio of 768x576.

Doesn't that 720-pixel resolution include 16 pixels of overscan? This is something I've never been clear about. I thought that the active picture area is 704 pixels and that's what should be scaled to a 4:3 display ratio.

[hello_hello]

I know that there is a set up aspect ratio in the MPEG header, but in my specific file the true resolution is 1024x576, not the playback resolution. I would like to stretch it back to 720x576 since I know that it is the original resolution.

That doesn't make sense to me. You can't change the resolution without resizing and re-encoding the video.

But does it mean, that videos are all recorded too narrow and just reproduced broadly? I've checked some normally looking 720x576 videos which get displayed by 1024x576. My conclusion is, that when it would be displayed in it's native resolutin, the video would look very weird.

It would look weird because the display aspect ratio would be wrong. For DVD video the resolution and display aspect ratio aren't the same.

Has your video been re-encoded or are you referring to the original mpeg2 source? You're not referring to a 4:3 PAL DVD that was incorrectly resized to 1024x576 when it was re-encoded are you? One that should have been resized to 768x576 and/or encoded with a 4:3 aspect ratio instead?

[jagabo]

PAL DVD is always 720x576* with either a 4:3 or 16:9 display aspect ratio (DAR). Either the player or TV will adjust for the DAR at playback. If the DVD is 16:9 DAR the the 720x576 frame is stretched horizontally to a ratio of 1024x576. If it's 4:3 DAR the frame is stretched to a ratio of 768x576.

Doesn't that 720-pixel resolution include 16 pixels of overscan? This is something I've never been clear about. I thought that the active picture area is 704 pixels and that's what should be scaled to a 4:3 display ratio.

Jeez, here we go again...

The DVD spec is quite clear: The flagged aspect ratio is the display aspect ratio and the full 720x480/576 frame comprises that DAR.

The problem is the DVD spec differs from the ITU digital video capture spec where DAR reflects the inner 704x480/576 portion of the frame and the extra 16 pixels of the width are padding (in case the capture is off center). DVDs made from analog tapes are usually captured via the ITU spec then written directly to DVD without correcting for the difference between the two specs. Nobody in the industry cares about the difference. Nobody can see the ~2 percent difference without measuring it. And anybody watching on an analog TV probably has a bigger error than that in the TV. DVD/BD players are usually schizophrenic on this issue. They follow the ITU spec on the composite/s-video outputs, the MPEG spec at the digital outputs. Ie, if you use an upscaling DVD player it will upscale the entire 720x480/576 16:9 frame to 1920x1080 at the HDMI output.

The DVD spec even has a provision for ITU caps -- just crop the frame down to 704 pixels. But nobody in the industry does that.

[hello_hello]

And the ambiguity still persists because the official mpeg4 pixel aspect ratios used for Bluray standard definition are almost identical to the ITU pixel aspect ratios and result in 4:3 having a display aspect ratio of around 1.364:1, and the same applies to 16:9 with an aspect ratio of around 1.819:1. The HDMI spec says 4:3 is exactly 4:3 and 16:9 is exactly 16:9 though, and most modern hardware players resize that way, at least via HDMI. Most software players resize to exactly 4:3 or 16:9 too.

My rule of thumb when encoding is to assume all 4:3 DVDs are ITU (ie 704x576 = 4:3) and all 16:9 DVDs are not ITU (ie 720x576 = 16:9) unless they have a large amount of crud down each side, in which case they might be ITU, or they might not.

[draig-llofrudd]

That doesn't make sense to me. You can't change the resolution without resizing and re-encoding the video.

Yes, I guess the video has been re-encoded. That is what I was thinking all the time and why I asked. [/QUOTE]

[DB83]

Well it's your prerogative to believe what you like and dismiss the opinion of those who know better than you.

Just do simple maths. 720*576 != 4:3 nor != 16:9 and you only have to read 'What is a DVD' (Check top of this page) to see that all dvds are 720*576.

But then a dvd does not store square pixels >> the variation depends whether you have a PAL or NTSC DVD.

And simple maths of 1024*576 does = 16:9. Still not convinced ?

And this has nothing to do with re-encoding. Correct 1:1 sizing yes since not all players/codecs will read Aspect Ratio flags. This flag is present on the original dvd which does then resize the stored image from 720*576 to 1204*576 for 16:9

[JVRaines]

Jeez, here we go again...

Thank you for a comprehensive explanation.

[KarMa]

Jeez, here we go again...

[aedipuss]

wow. lots of to do over nothing. 1024x576 is a perfectly acceptable correct size to rip a 16/9 pal dvd to in square pixel format like mp4. nothing else had to be said.