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 Post subject: Looking for a free multiple image grabber from video
PostPosted: Sat Nov 17, 2012 5:51 pm 
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I want to grab multiple images from a video but it seems more complicated than I expected. I found this site- http://www.labnol.org/software/extract- ... deo/18137/ . It talks about using VLC (which I have) command line but I don't really get what that is. Is it the same as command prompt? Yes I have searched but just got more confused. AV Cutty is in German and seems complicated. I also looked at ffmpeg but again they talk about command lines and I don't understand really what ffmpeg is anyway.
I can grab individual images easily but I need something where I can grab loads in one swoop.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sat Nov 17, 2012 6:05 pm 
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I don't have time to cook up a more useful answer, but yes, command line is the same thing as command prompt. You can bring it up by typing cmd from the start menu.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sat Nov 17, 2012 7:24 pm 
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TomZ wrote:
I don't have time to cook up a more useful answer, but yes, command line is the same thing as command prompt. You can bring it up by typing cmd from the start menu.

Thanks, that's a great help. I don't like playing around with that stuff unless I am sure I know what I am doing.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sun Nov 18, 2012 7:28 am 
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Tony, yes, you open a DOS window "Start - Run - cmd" and change to the folder where vlc is installed usually "C:\Program Files\VideoLAN\VLC\" (copy the path including the quotes, open the DOS window, right click, select paste and press return). Now you start vlc with the extra parameters to tell it what you want to capture: Note that if you put the video file in the same folder as vlc then "path to video file" = video file name (including extension type e.g. .avi., .mov etc.) Also, you should create a folder called images in the vlc installation folder, and let's say the video you have copied there is called vid.avi and you need the images for 1 second starting 301 seconds in:

vlc vid.avi --video-filter=scene --vout=dummy --start-time=301 --stop-time=302 --scene-ratio=1 --scene-prefix=img- --scene-path=images vlc://quit

(You can copy and paste the entire command string into the DOS window, just right click in the DOS box and select paste. I don't know why the forum software has made the final command a hyperlink, it is just text)

For me, this saved 23 files img00001.png to img00023.png in the folder images. For some reason img00001.png is blank, and img00002.png to img00012.png are zero size. I tried again with a time of 4 seconds, which created 74 files and only the first 3 were blank. :?

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sun Nov 18, 2012 12:37 pm 
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Tony, Gus' information is almost complete, let me fill in the blanks...

I don't know which system you have, but on Windows Vista 64-bit or Windows 7 64-bit, the default path for the standard 32-bit version of VLC is:
Code:
"C:\Program Files (x86)\VideoLAN\VLC"

Also, in DOS, to move to another directory, you need to add the "change directory" command (cd), so on the command prompt, you type the following (including the quotes), obviously the path might be different depending on your system and vlc version
Code:
cd "C:\Program Files (x86)\VideoLAN\VLC"

Once you are on vlc's folder, you can call vlc with options. Gus' list of parameters did not work for me, maybe it has something to do with the version of vlc. Here's one that works perfectly on VLC media player 2.0.3:
Code:
vlc videofile.avi --video-filter=scene --vout=dummy --start-time=25 --stop-time=30 --scene-format=png --scene-ratio=1 --scene-path=c:\images\ vlc://quit

On this first example, the file name is "videofile.avi" and I copied the file to the vlc folder for clarity. Also, I created a folder called "images" on the root of the C hard drive. This code will create a bunch of PNG files from second 25 to second 30 (like Gus said, some are empty, this might have something to do with vlc buffering). The "scene-ratio" is the ratio of frames to export (in this example, all frames are exported).

Here's another example, for clarity:
Code:
vlc d:\videos\videofile.avi --video-filter=scene --vout=dummy --start-time=5 --stop-time=10 --scene-format=png --scene-ratio=3 --scene-path=c:\images\ vlc://quit

On this second example, the file name is "videofile.avi" and it is in a folder called "videos" on the D hard drive. Again, the path for the exported images is a folder on the root of the C hard drive. This code will create a bunch of PNG files from second 5 to second 10 (like Gus said, some are empty). The "scene-ratio" in this example will export every third image only, but the file names remain the same, so technically, some files are missing.

More information about the vlc command line options can be found here: http://wiki.videolan.org/VLC_command-line_help

Skarabajo.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Mon Nov 19, 2012 1:28 pm 
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Thanks guys. I am running VLC portable (for some reason) on a 32 bit vista machine. I will have to read through everything written very carefully. I am amazed though there isn't any easier way to do it directly through some software editing program.

Edit: To make life easier I have now installed VLC 2.0.4

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Mon Nov 19, 2012 1:45 pm 
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You are welcome Tony, glad to help. :D

There are several ways to do this directly inside video editing/encoding software. For instance, the process takes a couple of clicks on Adobe Media Encoder.

But the problem was the restriction on the title of your first post; you wanted free software. :wink:

Skarabajo.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Mon Nov 19, 2012 1:51 pm 
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Whether or not VLC works for you seems dependent on the video format. I've tried this on a few different videos that play fine in real-time but when I have VLC extract scene images, most of them are zero-byte or not properly rendered.

Most video codecs don't actually store frames as individual images. There are lots of different tricks but there are usually "keyframes" that are stored intact and then later frames describe the delta from the keyframe to the next frame and then from the previous frame to the next frame. This includes motion vectors to anticipate where blocks of pixels are moving. Because of this it is non-trivial to extract a random frame of a video without rendering a bunch of previous frames. I suspect this is what is breaking VLC in my case.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Mon Nov 19, 2012 2:03 pm 
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Ok, I just tried this and after a few changes to the paths it works! Brilliant, thanks again.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sun Nov 25, 2012 3:02 pm 
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I have using this method for a few days now. Something that I noticed was that although the pictures are full size they are still very pixelated compared to a single grab within a program like Power Director. Is there any way of getting maximum quality? To be honest I am not sure if they are really usable.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sun Nov 25, 2012 5:32 pm 
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Tony,

Maybe this has something to do with what bmenrigh mentioned above; maybe not all the information on a given frame is stored as is. Maybe some of the information comes from other frames.

Do you have access to the Adobe Creative Suite? If so, this might work better in Adobe Media Encoder. Do you have a lot of these to do? Adobe Media Encoder can also work in with several files as input and even several files as output in one go.

In the meantime, maybe sharing some more data about the specific video files you want to convert might give us some clues on what is wrong. Information like: Codec, decoded format, resolution, pixel ratio, frame rate, number of streams (if more than one video stream), bit rate, etc.

Skarabajo.

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 Post subject: Re: Looking for a free multiple image grabber from video
PostPosted: Sun Nov 25, 2012 9:39 pm 
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This is now resolved. A kind forum member advised me to use Free-Video-to-JPG-Converter. It is far simpler than the command line stuff and quality is maintained.

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