[MEncoder-users] new doom9 codec comparission (submission)

[Corey Hickey]

Doom9 Feedback Hotline wrote:
> Hi
> 
> Alright, I'm done encoding. The lavc rip turned out surprisingly close on 
> target size (I've seen different in the past), but the Snow rip didn't. I 
> set the bitrate to 580 kbit/s, mencoder reports 519 kbit/s and the final AVI 
> is 57 MB below target size. I have attached the mencoder output for both 
> passes including the commandlines so you can verify that I did everything 
> correctly. As per the rules of the comparison, you have the possibility to 
> explain / amend settings but if I need to redo the encoding, I need to redo 
> it asap.
> 
> Regards
> Doom9 

Hmm. I'm not sure about this one, so I'm hoping somebody on
mencoder-users will know what to do.

The video you're encoding is 196160 frames long. My source is 196070
frames. I don't know where the discrepancy arises. Does avisynth alter
the length at all? Were there more than one release of The Matrix and I
got a different one?

Also, I was under the impression that mencoder would be handling the
cropping and scaling, but I see you're using pre-scaled video for the
source. That should work fine, but it might be that you're using
significantly different video data than I tested with.

I'm fairly sure the low bitrate on the second pass is because of the low
bitrate on the first. As you can see, it ended up being only 479.429
kbit/sec. Since I found that vqscale value specifically for the source I
have and the target bitrate (which is unchanged), the only thing I can
think of is that for some reason the video you are providing to your
mencoder requires fewer bits to encode at that quantizer than the video
I tested. If you don't have a different source DVD, than perhaps your
downscaling lost more detail/noise than mine did.

Without being able to test your source directly, I would suggest using
vqscale=1.5 instead of vqscale=2.15. Don't take that to be my final
answer, though; I'm hoping to get some insight from other people on
mencoder-users. vqscale=1.5 is based on looking at a graph I have of
quantizer vs bitrate for snow, and erring on the low side (1.8 is my
closest guess, but 1.5 should be safe).

-Corey

> ------------------------------------------------------------------------
> 
> mencoder.exe "D:\DVDs\THE_MATRIX_16X9LB_N_AMERICA\VIDEO_TS\matrix.avs" -ovc lavc -lavcopts vco
> dec=snow:vstrict=-2:cmp=1:subcmp=1:mbcmp=1:qpel:vqcomp=0.6:vpass=1:vqscale=2.15
> -o NUL:
> MEncoder dev-CVS-051123-22:21-4.0.2 (C) 2000-2005 MPlayer Team
> CPU: Advanced Micro Devices Athlon 64 Newcastle; Athlon 64 X2 Manchester (Family
> : 15, Stepping: 1)
> CPUflags: Type: 15 MMX: 1 MMX2: 1 3DNow: 1 3DNow2: 1 SSE: 1 SSE2: 1
> Compiled for x86 CPU with extensions: MMX MMX2 3DNow 3DNowEx SSE SSE2
> 
> success: format: 0  data: 0x0 - 0x73
> AVS file format detected.
> VIDEO:  [YV12]  640x272  12bpp  23.976 fps    0.0 kbps ( 0.0 kbyte/s)
> [V] filefmt:38  fourcc:0x32315659  size:640x272  fps:23.98  ftime:=0.0417
> Opening video filter: [expand osd=1]
> Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 0.000000, round: 1
> ==========================================================================
> Opening video decoder: [raw] RAW Uncompressed Video
> VDec: vo config request - 640 x 272 (preferred colorspace: Planar YV12)
> VDec: using Planar YV12 as output csp (no 0)
> Movie-Aspect is undefined - no prescaling applied.
> videocodec: libavcodec (640x272 fourcc=574f4e53 [SNOW])
> Using constant qscale = 2.150000 (VBR)
> Selected video codec: [rawyv12] vfm: raw (RAW YV12)
> ==========================================================================
> Writing AVI header...
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> Pos:8181.5s 196160f (100%) 16.63fps Trem:   0min   0mb  A-V:0.000 [479:0]
> Flushing video frames
> 
> Writing AVI index...
> Fixing AVI header...
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> 
> Video stream:  479.429 kbit/s  (59928 B/s)  size: 490306587 bytes  8181.515 secs
>   196160 frames
> 
> mencoder.exe "D:\DVDs\THE_MATRIX_16X9LB_N_AMERICA\VIDEO_TS\matrix.avs" -ovc lavc -lavcopts vco
> dec=snow:vstrict=-2:cmp=1:subcmp=1:mbcmp=1:qpel:vqcomp=0.6:vpass=2:vbitrate=580
> -o "d:\matrix-snow.avi"
> MEncoder dev-CVS-051123-22:21-4.0.2 (C) 2000-2005 MPlayer Team
> CPU: Advanced Micro Devices Athlon 64 Newcastle; Athlon 64 X2 Manchester (Family
> : 15, Stepping: 1)
> CPUflags: Type: 15 MMX: 1 MMX2: 1 3DNow: 1 3DNow2: 1 SSE: 1 SSE2: 1
> Compiled for x86 CPU with extensions: MMX MMX2 3DNow 3DNowEx SSE SSE2
> 
> success: format: 0  data: 0x0 - 0x73
> AVS file format detected.
> VIDEO:  [YV12]  640x272  12bpp  23.976 fps    0.0 kbps ( 0.0 kbyte/s)
> [V] filefmt:38  fourcc:0x32315659  size:640x272  fps:23.98  ftime:=0.0417
> Opening video filter: [expand osd=1]
> Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 0.000000, round: 1
> ==========================================================================
> Opening video decoder: [raw] RAW Uncompressed Video
> VDec: vo config request - 640 x 272 (preferred colorspace: Planar YV12)
> VDec: using Planar YV12 as output csp (no 0)
> Movie-Aspect is undefined - no prescaling applied.
> videocodec: libavcodec (640x272 fourcc=574f4e53 [SNOW])
> Selected video codec: [rawyv12] vfm: raw (RAW YV12)
> ==========================================================================
> Writing AVI header...
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> Pos:8181.5s 196160f (100%) 17.46fps Trem:   0min 508mb  A-V:0.000 [519:0]]
> Flushing video frames
> 
> Writing AVI index...
> Fixing AVI header...
> ODML: Aspect information not (yet?) available or unspecified, not writing vprp h
> eader.
> 
> Video stream:  519.393 kbit/s  (64924 B/s)  size: 531178202 bytes  8181.515 secs
>   196160 frames