libavdevice/vfwcap.c memory allocation error

[Rick Winkelman]

vfw_read_header()

line 358 a structure memory area is freed

av_free(bi);

a few lines later, lines: 384 & 385 the freed memory are is used.

codec->width = bi->bmiHeader.biWidth;
codec->height = bi->bmiHeader.biHeight;

by debugging it, i have found the memory is already been used and corrupted. This causes erratic behavior with ffmpeg.exe

I tried the obvious corrections by copying the height and width values from the memory (bi) values before the free, and then used the copied values to set the codec values. This causes a hang in av_read_packet()
in ffmpeg.exe and an abort when debugged using eclipse.

[Carl Eugen Hoyos]

This is a regression since 3e15ea21504a5cc1765afd78dd72ef486a10a27b.

commit 3e15ea21504a5cc1765afd78dd72ef486a10a27b
Author: Anton Khirnov <​anton@khirnov.net>
Date: Tue May 24 07:43:01 2011 +0200

vfwcap: add video_size private option.

[reimar]

I just sent a patch, it would be great if you could help by testing it.
​http://ffmpeg.org/pipermail/ffmpeg-devel/2011-August/114238.html