[Libav-user] Building with MSVC toolchain resulting in seeking problem?

John Orr john.orr at scala.com
Tue Mar 12 16:04:07 CET 2013

On 3/12/2013 5:47 AM, Bjoern Drabeck wrote:
> Hi,
> as described in the ffmpeg documentation 
> http://ffmpeg.org/platform.html#Windows under 4.2, I have set up 
> MinGW/MSys to compile using the MSVC toolchain and c99-to-c89 tool. I 
> have got that to build, however compared to builds from the zeranoe 
> site (and also builds I have asked a friend of mine to make for me 
> using mingw with gcc), I always end up with seeking problems.

I think the MSVC builds use 32-bit fstat and lseek functions, so they 
don't play or seek correctly with files > 2GB.

I modified file_seek in libavformat/file.c locally like this:

/* XXX: use llseek */
static int64_t file_seek(URLContext *h, int64_t pos, int whence)
     FileContext *c = h->priv_data;
     int64_t ret;

     if (whence == AVSEEK_SIZE) {
#ifndef _MSC_VER
         struct stat st;

         ret = fstat(c->fd, &st);
         struct _stat64 st;
         ret = _fstati64( c->fd, &st );
         return ret < 0 ? AVERROR(errno) : (S_ISFIFO(st.st_mode) ? 0 : 
#ifndef _MSC_VER
     ret = lseek(c->fd, pos, whence);
     ret = _lseeki64(c->fd, pos, whence);
     return ret < 0 ? AVERROR(errno) : ret;


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