记录一种avi文件

第一次见到这种avi文件，下面是用MPlayer播放的输出，无图像，

==========================================================================
Opening video decoder: [vfwex] Win32/VfWex video codecs
Loading codec DLL: 'vp7vfw.dll'
Win32 LoadLibrary failed to load: vp7vfw.dll, /usr/lib/win32/vp7vfw.dll, /usr/local/lib/win32/vp7vfw.dll
Can't open library vp7vfw.dll
ICOpen failed! unknown codec / wrong parameters?
VDecoder init failed :(
Cannot find codec matching selected -vo and video format 0x30375056.
Read DOCS/HTML/en/codecs.html!
==========================================================================
==========================================================================
Trying to force audio codec driver family libmad...
Opening audio decoder: [libmad] libmad mpeg audio decoder
AUDIO: 48000 Hz, 2 ch, s16le, 128.0 kbit/8.33% (ratio: 16000->192000)
Selected audio codec: [mad] afm: libmad (libMAD MPEG layer 1-2-3)
==========================================================================
AO: [pulse] Init failed: Connection refused
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
Video: no video
Starting playback...
A:   1.2 (01.1) of 11377.3 ( 3:09:37.3)  1.1%
Exiting... (Quit)

显然需要安装解码，于是下载并安装了 ，出画像了。用file查一下它的格式:

 RIFF (little-endian) data, AVI, 576 x 384, 23.98 fps, video:, audio: MPEG-1 Layer 3 (stereo, 48000 Hz)

一般来说，用file查看视频文件，在video:后面应该有具体的视频格式，曾经见过的avi文件的视频格式是DivX和XviD，但这里在video:后面没有告诉视频格式，还说需要.dll，说不清是不是微软的什么技术。