Autocrop adjust movie size or not

[Xonk]

Hi all once again. ffmpeg has been working great recently, I just had a question with the cropping/autocrop feature. (I am converting a VIDEO_TS to divX)

After I open the folder with ffmpegx, select the preset and adjust the movie length, I head down to the Filters Tab and select autocrop. It correctly finds the values needed to crop the movie at, which I confirm with the preview.

However, the cropped movie ratio is not the same as the output movie size selected in the video tab. Basically, the movie size never changes to compensate what the Autocrop says.

Is there something different I should be doing, or do I have to manually calculate (woohoo subtraction) the new size of the cropped movie and handle the movie size manually?

[major]

The autocropping should correctly adjust the movie size. Please provide an example with actual numbers -before/after cropping-, explain what you get and why you think it's not correct.

[Xonk]

Alright. When the folder is first opened, the video size is 720 x 480 (with menus set to 3:2 and NTSC FILM).

After doing the preset, it doesn't change anything.

I then go to the Filters tab, set the Preview to 10 min, and hit autocrop. I get these numbers: 720 360 0 60

Clicking back to the Video tab, the Size remains unchanged. It is still 720x 480 at 3:2 with NTSC FILM.

If I then go to the Bitrate calculator, put in the movie length (160 min), do 2 CDs, and click Auto, it does adjust.

The new numbers are 544 x 352. However, I am pretty sure this is not the ratio of the cropped movie. If I am reading the autocrop numbers right, the cropped movie is 720 x 360, or a ratio of 2:1. 544 x 352 is a ratio of 3:2.

Interestingly enough, if I then go back to the autocrop and hit it again, it gives me the same cropping numbers, but the video tab is reset. It goes back to the old Video Bitrate and the old video size of 720 x 480.

[major]

Alright. When the folder is first opened, the video size is 720 x 480 (with menus set to 3:2 and NTSC FILM).

Before autocropping, you must manually set the source movie ratio which may be eg. 16:9 or 2.35:1.

[Xonk]

Maybe I am misunderstanding you, but the source movie (before cropping) is 720x480, or a 3:2 ratio already. With the cropping, it goes to a 2:1 ratio, which isn't on the list.

Here is the text output at the top of the window, talking about the source:

VIDEO: mpeg-2, size: 720x480, 23.976 fps w/3:2, 7500 kbps. AUDIO: ac3, 48000Hz, 384 kbps.

[major]

There are two ratios. The physical image of a DVD has always the same size and ratio and you should not care about it. What matters, is that inside that rectangle, there is a movie, which has its own playback ratio. Typically it is 2.35:1, and sometimes 16:9, or 4:3. You can easily tell which one it is by looking at the image during full-screen playback. That is the ratio that you must specify and which will be used for resizing when you click "autocrop".

[Xonk]

There are two ratios. The physical image of a DVD has always the same size and ratio and you should not care about it. What matters, is that inside that rectangle, there is a movie, which has its own playback ratio. Typically it is 2.35:1, and sometimes 16:9, or 4:3. You can easily tell which one it is by looking at the image during full-screen playback. That is the ratio that you must specify and which will be used for resizing when you click "autocrop".

Alright, that all makes sense, thanks. But now I have another problem. The movie ratio that is inside that rectangle is 2:1, which I don't see on the ratio menu.

Looking around some, I guess I have to use the "Unconstrained" and manually type in a ratio of 2:1, is that correct?

[major]

To decide the source movie ratio you can't simply divide width/height. The pixels may be not square, the movie could be anamorphic, etc. You should, instead, look at the movie during playback. Does it look like normal TV? Use 4:3. Does it look like widescreen TV? Use 16:9. Does it look like a feature movie Cinemascope? Use 2.35:1. In almost all cases you have to choose between those values. If the ratio is really different (which is unlikely) you should apply the ratio after cropping by setting manually the image width and height.

[yonidass]

Xonk, if you're not sure about exactly which ratio to use, try making a 5 second test clip and then comparing the clip to the preview. Enlarge your clip (assuming you make it smaller than the original) until it's the same as the original preview. Both height and width should be exactly the same size no matter what size you encode with, as long as the ratio is the same.

Note: revent versions of ffmpegx now take a long time to pre-scan video_ts folders, even before making a 5 second clip (at least mine does). One way to get around this is to open Apple's Activity Monitor in the Utilities folder and quit mencoder right after you hit encode. This will stop the pre-scan and start the encoding. Not recommended for encoding the entire movie.