DV PAL Resolution is stretching when transcoding??

[Gibson's Squares]

I'm digitising PAL VHS using a Canopus ADVC-100 & iMovie, and MediaInfo reports the resulting DV files to be:

Width : 720 pixels
Height : 576 pixels
Display aspect ratio : 4:3


When I transcode to DivX using ffmpegx, I set the frame size to be the same, 720 x 576, but MediaInfo reports the exported AVI as:

Width : 720 pixels
Height : 576 pixels
Display aspect ratio : 5:4

And when I flick between the two files in VLC, the AVI is stretched vertically.


If I compare them in QuickTime the DV is much wider, and actually has two dimensions listed:
Format: DV, 720 x 576 (768 x 576), Millions

Whereas the AVI has one dimension:
Format: DivX 6.0, 720 x 576, Millions


Can someone explain what is happening? How can the DV have two values? Is it some kind of embedded exif info?

How can I make the DivX behave the same as the DV within media players? I basically want an exact same size transfer from DV to AVI, and I can't tell if I've got it!

[hech54]

I'm probably wrong but....shouldn't DV be 640 x 480?

[DB83]

DV has a capture ratio for PAL at 720*576 pixels. But it has the display flag set at 4:3. That means AFAIK it adjusts to 768*576 when displayed.

A pixel for pixel copy at 720*576 Divx would give you a 5:4 aspect ratio. So you either reencode to 768 to 576 or, more commonly, 720*544(or 540)

And if you want a simple 4:3 DIVX you encode at 640*480

[poisondeathray]

Not sure of the equivalent programs on a mac but you can use mpeg4modifier on a windows machine to set the DAR flag for xvid/divx encodes . The xvid vfw interface also has this ability.

I think in ffmpeg CLI you can set -aspect 4:3 , not sure how to do it with ffmpegx

Or you can do as DB83 suggests and use square pixels (resize to 640x480)

[Gibson's Squares]

Ahh.. that's exactly what I want to do - change the display flag without re-encoding or changing the physical dimensions of the file.

There must be some program on the mac that does this??

I tried setting the display dropdown to 4:3 in ffmpegx and then putting the dimensions to 720*576, but it ignored the aspect ratio and set it to 5:4. I think that dropdown is to auto calculate a 4:3 ratio rather than set it.

If I ever manage to use ffmpeg from the command line, can you specify a 4:3 flag with it even though you might be exporting a non 4:3 file?

[Gibson's Squares]

Anyone got any more suggestions how I can do this on a Mac?

[DB83]

I would ask a moderator to move this topic to the dedicated Mac forum (when I first replied I did not appreciate it was Mac related).

You are likely to get more answers there then in this general/Windows area.

[poisondeathray]

Avidemux allows you to set PAR for xvid encoding, and it works

But there are differences between the PC version and Mac version, but you can give it a try

"AVI" is a windows format, designed by Microsoft. So proper support on a Mac is "dicey" at best

Are you encoding interlaced xvid? (since you have VHS source, and using DV)

[Gibson's Squares]

Good idea DB83.

Yes, am transcoding the DV to xvid. Still undecided on whether to keep the interlacing, but probably will in this instance.

[Baldrick]

Moving you to our mac section.

[Herve]

Ahh.. that's exactly what I want to do - change the display flag without re-encoding or changing the physical dimensions of the file.

There must be some program on the mac that does this??

use my soft : launch it > menu item "Windows" > "Studio…" : "Modify"
PS: the app is a shareware but your don't have to register to use this module

PPS: 5:4 is the "native pixels contents" ratio (whitout any aspect flag, nor 4:3 nor 16:9). So -during encoding- you forget to specify the aspect…

PPPPPPPPs: gimme some news about the modify module, I wrote it to handle 4:3<->16:9, not to handle from noting to something (so I didn't tested your exact need )

bye

[Gibson's Squares]

Thanks Herve, will give it a try.

In the install assistant, what is the difference between selecting 'Broadcasting' and 'Editing'?

What will each option do to my files?

[Gibson's Squares]

Just seen neither Herve's MovieConverter-Studio nor the earlier suggested Avidemux support DV, which is my input format. Bahhh!

Can anyone confirm that using ffmpeg within Terminal to set '-aspect 4:3' (even if the video isn't truly 4:3) will result in the output XviD file playing as 4:3 in media players?

[poisondeathray]

No, I tested it and ffmpeg's -aspect switch seems broken with xvid

avidemux supports dv-avi (.avi container), but you probably have .dv . You might be able to rewrap it to dv-avi with mpegstreamclip (or ffmpeg can for sure)

...even if the video isn't truly 4:3

The DAR is truly 4:3 . The Frame Aspect Ratio is 5:4 (because 720 / 576 = 5:4)

[poisondeathray]

Supposedly you can run mpeg4modifier (even the GUI version) on linux or mac with mono
http://www.mono-project.com/Main_Page

See details here
http://forum.doom9.org/showthread.php?t=117553

[Herve]

In the install assistant, what is the difference between selecting 'Broadcasting' and 'Editing'?

you don't mind, assistant if for "the whole stuff", not for your specific use

[Herve]

oops (seems I mistaook your needs)

Can anyone confirm that using ffmpeg within Terminal to set '-aspect 4:3' (even if the video isn't truly 4:3) will result in the output XviD file playing as 4:3 in media players?

"no", …not really
official AVI specifications do not support anamorphous files (aka DisplayAspectRatio = a forced display). Some players do, but it's not compliant with the norm, so avoid it to obtain a reliable result.
So, you have to manually convert anamorphous pixels to square pixels, during encoding to Xvid
eg:
- your input file is "an anamorphous file that have to be displayed as 4:3", just make a real 4:3 file: eg: force/scale pixels weight to 640 and height to 480
- your input file is "an anamorphous file that have to be displayed as 16:9", just make a real 16:9 file: eg: force/scale pixels weight to 640 and height to 360

An encoding step is the most reliable way to do (forget the "flag change step", here, it's not really a good feature for your need)
bye

[Gibson's Squares]

No, I tested it and ffmpeg's -aspect switch seems broken with xvid

official AVI specifications do not support anamorphous files (aka DisplayAspectRatio = a forced display). Some players do, but it's not compliant with the norm, so avoid it to obtain a reliable result.

Is this why Poisondeathray's test in ffmpeg failed? It's perhaps not that ffmpeg was broken, but that XviD/AVI doesn't support it?

Maybe I'll have to choose another end format. What formats support ratio flags?

I know I could force the video into a square pixel/4:3 size, but I really wanted to keep it as it was.

[manono]

I know I could force the video into a square pixel/4:3 size, but I really wanted to keep it as it was.

Bah. You'll never be able to tell the difference. Don't forget your source is a crummy VHS tape.

[poisondeathray]

No, I tested it and ffmpeg's -aspect switch seems broken with xvid

official AVI specifications do not support anamorphous files (aka DisplayAspectRatio = a forced display). Some players do, but it's not compliant with the norm, so avoid it to obtain a reliable result.

Is this why Poisondeathray's test in ffmpeg failed? It's perhaps not that ffmpeg was broken, but that XviD/AVI doesn't support it?

Maybe I'll have to choose another end format. What formats support ratio flags?

I know I could force the video into a square pixel/4:3 size, but I really wanted to keep it as it was.

That's true about the spec, but it's definitely limited to ffmpeg implementation. It works with mpeg4modifier encoding through offical xvid/vfw encoding (as well as avidemux). I can post some examples if you want.

If you read that thread linked, some mac user on older osx version used mpeg4modifer through mono and reported it working

Most hardware players seem to be fine with it (In fact I haven't seen any DivX DVD player that doesn't, and most software players seem fine with it as well)


Having said that, you can use h.264 (Better quality and compression than xvid anyway) with mp4 or mkv container which officially support "non square pixels" both in the stream information, and container flags. It depends on how you intend to view it and what devices. Many newer devices support mp4, mkv containers and h.264 compression. Some only support mp4.

[Herve]

(about DAR)[QUOTE=poisondeathray;2166832]

Most hardware players seem to be fine with it

I didn't say it does not work, I just said is not reliable (for .AVI/"Divx", it's safer to always use square pixels )

bye

Edit: typo

[Gibson's Squares]

I've been giving h.264 a whirl since reading up on its superior compression, and wrapping it in MP4.

By chance I then found a mac tool called MP4tools which does change the ratio flag of an MP4 to 4:3.
I can't work out yet if it's re-encoding the video to do this, but it's very quick so I suspect not.