Extracting basic info from animation file

Question

I'm writing an application that handles metadata for images and all kinds of animations, so I'm looking for a way to find basic info about an animation file, e.g:

• length (in minutes/seconds/frames)
• aspect ratio of pixels
• resolution of individual frames
• framerate

Right now, I let my program execute

mplayer -identify animfile.avi

and parse its console output, which contains all the info I need in a machine-readable format. This works fine, but I know that some potential users of the program prefer vlc as a media player so I'd rather avoid having a hard dependence on mplayer being installed.

I've tried

vlc -vv animfile.avi

which prints an ungodly amount of junk on the console, sometimes containing the stuff I'm looking for. The formatting and what data gets printed seems to vary depending on the file format of the animation though.

Is there an easier way to extract basic info from an animation of any format one has a decoder for (especially the length of the animation) using vlc or som other app/library that is usually available on a typical Linux installation?

Edit: I'd rather use another program to do the dirty work, as this is supposed to work for any animation format, e.g avi, mpg, mov, wmv, vob etc.

Edit: totem-video-indexer seems more promising, and was also included with the standard installation. Enough codecs to make it useful, however, was not. That could be fixed by installing the "non-free-codecs" package from medibuntu.

Answer 1

The output of totem-video-indexer is very easy to parse:

TOTEM_INFO_DURATION=5217
TOTEM_INFO_HAS_VIDEO=True
TOTEM_INFO_VIDEO_WIDTH=720
TOTEM_INFO_VIDEO_HEIGHT=480
TOTEM_INFO_VIDEO_CODEC=XVID MPEG-4
TOTEM_INFO_FPS=30
TOTEM_INFO_HAS_AUDIO=True
TOTEM_INFO_AUDIO_BITRATE=50
TOTEM_INFO_AUDIO_CODEC=MPEG 1 Audio, Layer 3 (MP3)
TOTEM_INFO_AUDIO_SAMPLE_RATE=48000
TOTEM_INFO_AUDIO_CHANNELS=Stereo

Answer 2

This is a little more difficult question than you may realize. The AVI file format grew over time, and often has nearly the same information in two or three different places. In some cases those are really supposed to agree (but sometimes don't) and in other cases they're subtly different.

Just for example, you asked about the width and height. There are actually four different width/height specs for a single frame: the screen width/height, the pixel width/height (from which you derive the pixel aspect ratio), the active width/height, and the compressed width/height. The frame width and height is the (theoretical) size of the screen. The active width/height excludes the overscan area. The compressed width/height takes into account rounding -- for example, JPEG compresses in blocks of 8x8 pixels, so the compressed width and height have to be multiples of 8 for a motion JPEG file. The active width/height tells you if (for example) some pixels at the border should be ignored.

In any case, since your question is tagged C++, I'm going to guess you'd rather read the file and get the data directly than depend on spawning something else to do the dirty work. If so, you probably want to look at the OpenDML AVI file spec. You can get at least some idea of the length, resolution, and framerate just from reading the basic AVI header, which is in a fixed spot at the beginning of the file, so that much is trivial to get. It'll take a bit more work to get to the pixel aspect ratio though...

Answer 3

mediainfo is a pretty useful program. It's LGPL, and is just a frontend for libmediainfo, which should be exactly what you want.

http://mediainfo.sf.net/