Extracting frames from VOB files

[omkar.parkhi]

Hi,
I have PAL 720x576 formatted VOB file.
Display aspect ratio is set to 16:9
I want to extract frames from this file with size 720x405.
I can specify the size in ffmpeg while extracting. Is there
any other way to extract the frames with this resolution?
Do I need to change VOB header somewhere?

Regards,
Omkar

[hech54]

What is "extracting frames"?

[omkar.parkhi]

I want to save every frame of this video in 720x405 format as a jpeg file

[omkar.parkhi]

What I essentially want to do is set aspect ratio of the VOB file to 16:9 720x405 without reencoding the video.

[titigrom]

VirtualdubMod can open your VOB, you apply the resize filter to output 720*405. Save "image sequence" as bmp and later convert your files to jpeg

[intracube]

ffmpeg -i video.vob -vf scale=720:405 -qscale 1 image%04d.jpg

The command will obviously generate a lot of files, so it would be a good idea to create an empty folder for the conversion.

'-qscale' controls the quality (and filesize) of the jpeg images. A lower value = higher quality (bigger jpegs).

The formatting of the image filenames can be changed:
'image%04d.jpg' will create jpegs with the filenames image0001.jpg, image0002.jpg, image0003.jpg
'image%02d.jpg' will create jpegs with the filenames image01.jpg, image02.jpg, image03.jpg
'image%08d.jpg' will create jpegs with the filenames image00000001.jpg, image00000002.jpg, image00000003.jpg etc

You can also output png, tga, tif images by changing the extension:
image%04d.png for example.

[omkar.parkhi]

Ok, What changes should I make to the header so that any player will stream it as 720x405?

[omkar.parkhi]

Hi intracub, thanks.. I was told that if I change some headers of the VOB file, I can use ffmpeg without vf scale option and it will extract 720x405 files. Is there any way to do it?

[intracube]

I want to save every frame of this video in 720x405 format as a jpeg file

What I essentially want to do is set aspect ratio of the VOB file to 16:9 720x405 without reencoding the video.

You can change the aspect ratio of a VOB file to 16:9 without re-encoding, but that doesn't involve changing the resolution - the resolution will still be 720x576.

Hi intracub, thanks.. I was told that if I change some headers of the VOB file, I can use ffmpeg without vf scale option and it will extract 720x405 files. Is there any way to do it?

You're asking several different questions. What is your end goal?

Do you want to create a directory of jpeg images from a .vob file? Or simply change the aspect ratio of a vob without re-encoding it?

[omkar.parkhi]

Hi, my end goal is to create directory of jpeg images of size 720x405 from vob.
This can be done using ffmpeg scaling parameter as you have shown.
Can I change the VOB aspect ratio and not use ffmpeg scaling parameter?
Meaning, after I fix VOB AR flags if I run
ffmpeg -i video.vob -qscale 1 image%04d.jpg
I get images of size 720x405?

[intracube]

Can I change the VOB aspect ratio and not use ffmpeg scaling parameter?
Meaning, after I fix VOB AR flags if I run
ffmpeg -i video.vob -qscale 1 image%04d.jpg
I get images of size 720x405?

I don't think ffmpeg will do that.

I've just experimented with a couple of VOB files. One is 4:3, the other is 16:9 (both are the same resolution - 720x576). In both cases ffmpeg outputs images with the same resolution as the original VOB files (720x576). The scale filter is the only way I've found to force a custom resolution.

Also, if your VOB file is interlaced, you might want to add the yadif filter to deinterlace the video and avoid jaggies on the outputted images:
ffmpeg -i video.vob -qscale 1 -vf yadif=0,scale=720:405 image%04d.jpg

It should be possible to use 'yadif=1' and output one image for each video field. However this doesn't seem to work when outputting images - only 'yadif=0' works as expected (one image for each pair of fields).