[MPlayer-dev-eng] gcc 2.95 bug/oddity?

[Diego Biurrun]

Diego Biurrun writes:
> 
> I'm experiencing a peculiar bug that nobody can reproduce, when
> playing
> 
> http://mplayerhq.hu/~diego/cathedral-beta2-400extra-crop-avc.mp4
> http://mplayerhq.hu/~diego/nature_704x576_25Hz_1500kbits.h264
> 
> playback fails with the following errors:
> 
> Movie-Aspect is nan:1 - prescaling to correct movie aspect.
> VO Config (704x576->704x-2147483648,flags=0,'MPlayer',0x32315659)
> VO: invalid dimensions!
> FATAL: Cannot initialize video driver.
> 
> I usually use gcc 2.95.4, if I recompile libmpcodecs/vd.c with gcc 3.3
> the error goes away, changing -O4 to -O0 and/or -march=pentium,
> -mcpu=pentium does not help.
> 
> In libmpcodecs/vd.c line 125 the following variable is declared:
> 
> float movie_aspect=-1.0;
> 
> and tested in line 262:
> 
>   if(movie_aspect>-1.0) sh->aspect = movie_aspect; // cmdline overrides autodetect
> 
> If I change the initialization of movie_aspect to 0, the problem goes
> away, but I haven't read the code in depth to understand what it is
> supposed to be doing.
> 
> Can anybody give me some further clues about this?  Is this a compiler
> bug and/or what should I investigate to verify this?

I've been digging through the code some more and found the following:

The problem appears to originate in libmpcodecs/vd_ffmpeg.c line 464

  float aspect= av_q2d(avctx->sample_aspect_ratio) * avctx->width / avctx->height;

aspect is used a few lines below to set sh->aspect.

Now after adding a few printfs throughout the code it appears to be

  av_q2d(avctx->sample_aspect_ratio)

that returns nan and thus aspect is nan. av_q2d is defined in
libavcodec/rational.h as

  /**
   * converts the given AVRational to a double.
   */
  static inline double av_q2d(AVRational a){
      return a.num / (double) a.den;
  }

I'm stuck there for the moment.  Michael, can you comment on this?
It's your code..

Diego