[Ffmpeg-devel] Illegal instruction error for ffmpeg and x264 on Intel iMac

Laine Lee llee
Fri Mar 31 23:46:22 CEST 2006

I have managed to isolate the problem to the x264 Intel-built executable by
creating an intermediate file rather than piping ffmpeg output to x264. I
used a small test file of just under 7 seconds of mpeg2 video.

When run on the Intel, the following ffmpeg command is successful:

$ ffmpeg -i /video.mpg  -s 320x240 -pix_fmt yuv420p -f rawvideo

When run on the Intel, the following x264 command is successful only if the
version of x264 used is compiled for PPC (output results included):

$ x264 -o /output.mp4 /intermediate.y4m 320x240

x264 [info]: using cpu capabilities Altivec
mp4 [info]: initial delay 0 (scale 25)
x264 [info]: slice I:3     Avg QP:23.00  size:  3259  PSNR Mean Y:44.50
U:46.44 V:47.81 Avg:45.20 Global:45.07
x264 [info]: slice P:166   Avg QP:26.00  size:   575  PSNR Mean Y:42.71
U:45.22 V:46.46 Avg:43.51 Global:43.38
x264 [info]: mb I  I16..4: 57.3%  0.0% 42.7%
x264 [info]: mb P  I16..4: 13.9%  0.0%  0.7%  P16..4: 31.5%  9.5%  0.9%
0.0%  0.0%    skip:43.5%
x264 [info]: PSNR Mean Y:42.737 U:45.246 V:46.482 Avg:43.540 Global:43.410

encoded 169 frames, 2.95 fps, 125.14 kb/s

Here are the results if the same command is issued to the Intel-built x264:

$ x264 -o /output.mp4 /intermediate.y4m 320x240
could not open input file '/intermediate.y4m'

The Intel-built version of x264, although apparently successfully compiled,
appears to be incapable of performing the task at hand.

Laine Lee

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