！关于linux下执行mencoder命令的问题

Question

我在linux服务器命令行环境下执行mencoder来转换wmv2格式的视频文件  和  用户php的exec执行同样的命令，文件转换出来的大小不一样，申明命令一摸一样。

以下是用exec执行的结果
MEncoder 1.0pre8-3.4.4 (C) 2000-2006 MPlayer Team CPU: Intel(R) Xeon(TM) CPU 3.06GHz (Family: 15, Model: 2, Stepping: 9) CPUflags: Type: 15 MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1 Compiled for x86 CPU with extensions: MMX MMX2 SSE SSE2 success: format: 0 data: 0x0 - 0x7c1792 ASF file format detected. VIDEO: [WMV2] 320x240 24bpp 1000.000 fps 0.0 kbps ( 0.0 kbyte/s) [V] filefmt:6 fourcc:0x32564D57 size:320x240 fps:1000.00 ftime:=0.0010 ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders AUDIO: 32000 Hz, 2 ch, s16le, 40.0 kbit/3.91% (ratio: 5000->128000) Selected audio codec: [ffwmav2] afm: ffmpeg (DivX audio v2 (FFmpeg)) ========================================================================== OK, exit Opening video filter: [expand osd=1] Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 0.000000, round: 1 Opening video filter: [scale w=320 h=240] ========================================================================== Opening video decoder: [dshow] DirectShow video codecs Win32 LoadLibrary failed to load: wmv8ds32.ax, /usr/local/lib/codecs/wmv8ds32.ax, /usr/lib/win32/wmv8ds32.ax, /usr/local/lib/win32/wmv8ds32.ax Warning: DS_Filter() could not open DirectShow DLL. (DLL=wmv8ds32.ax, r=0x857c89f) Failed to create DirectShow filter You need to upgrade/install the binary codecs package. Go to http://www.mplayerhq.hu/dload.html VDecoder init failed Opening video decoder: [dmo] DMO video codecs Win32 LoadLibrary failed to load: wmvdmod.dll, /usr/local/lib/codecs/wmvdmod.dll, /usr/lib/win32/wmvdmod.dll, /usr/local/lib/win32/wmvdmod.dll IMediaObject ERROR: 0x859282a could not open DMO DLL (0x0 : 0) Failed to create DMO filter You need to upgrade/install the binary codecs package. Go to http://www.mplayerhq.hu/dload.html VDecoder init failed Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family Selected video codec: [ffwmv2] vfm: ffmpeg (FFmpeg M$ WMV2/WMV ========================================================================== Forcing output FourCC to 31564c46 [FLV1]. VDec: vo config request - 320 x 240 (preferred colorspace: Planar YV12) VDec: using Planar YV12 as output csp (no 0) Movie-Aspect is undefined - no prescaling applied. SwScaler: using unscaled Planar YV12 -> Planar YV12 special converter videocodec: libavcodec (320x240 fourcc=31564c46 [FLV1]) VIDEO CODEC ID: 22 AUDIO CODEC ID: 15001, TAG: 0 Writing header... Pos: 0.1s 1f ( 1%) 0.00fps Trem: 0min 0mb A-V:0.000 [0:0] Pos: 0.1s 2f ( 1%) 0.00fps Trem: 0min 0mb A-V:0.003 [0:0] Pos: 0.1s 3f ( 1%) 0.00fps Trem: 0min 0mb A-V:0.007 [0:0] Pos: 0.2s 4f ( 1%) 0.00fps Trem: 0min 1mb A-V:0.013 [0:0] Pos: 0.3s 5f ( 1%) 0.00fps Trem: 0min 1mb A-V:0.020 [0:0] Pos: 0.3s 6f ( 1%) 0.00fps Trem: 0min 2mb A-V:0.026 [0:0] Pos: 0.3s 7f ( 1%) 0.00fps Trem: 0min 2mb A-V:0.030 [0:0] Pos: 0.4s 8f ( 1%) 0.00fps Trem: 0min 2mb A-V:0.033 [0:0] Pos: 0.5s 9f ( 1%) 0.00fps Trem: 0min 2mb A-V:0.040 [0:0] Pos: 0.5s 10f ( 1%) 0.00fps Trem: 0min 2mb A-V:0.046 [0:0] Pos: 0.5s 11f ( 1%) 0.00fps Trem: 0min 2mb