X264 Stats Output

From MeWiki

Typical x264 output on default log-level:

avis [info]: 1280x720 @ 1.77 fps (40997 frames)
yuv4mpeg: 640x480@30/1fps, 0:0
x264 [info]: 352x288 (given by file name) @ 25.00 fps

Depending on your input source, you should see one of these lines in some form. they correspond to avisynth, y4m, and yuv input respectively.

These lines are specific to the x264 CLI and are not displayed when using libx264.

x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64

Note this does not necessarily match up with the capabilities your CPU has. On some chips, x264 won't use a certain instruction set as it is actually slower.

x264 [info]: profile High 4:2:2, level 3.1, 4:2:2 8-bit

Information on the h264 profile, selected colorspace and level for the stream. The profile is implied by the options used (eg, B-frames implies at least main profile, 8x8dct implies at least high profile) and is given here for information only. The level is a number written into the bitstream. You can either explicitly set the level you want with --level, or not do so and let x264 guess (reasonably accurately). Bit depth displayed along with level (depends from build or encoding options).

x264 [info]: frame I:461   Avg QP:16.16  size: 51489  PSNR Mean Y:45.96 U:50.20 V:49.59 Avg:46.85 Global:44.69
x264 [info]: frame P:11836 Avg QP:17.35  size: 28198  PSNR Mean Y:42.89 U:47.43 V:46.95 Avg:43.81 Global:42.82
x264 [info]: frame B:28700 Avg QP:16.99  size: 11522  PSNR Mean Y:41.85 U:45.69 V:45.32 Avg:42.68 Global:42.27

For each of the three frame types, show the total number of frames, the average quantizer of every macroblock in the frame type, the average size of said frame type, and PSNR results (if requested).

x264 [info]: consecutive B-frames:  3.5% 10.8% 20.6% 28.2% 16.8%  4.5% 15.6%

Percentage of consecutive B-frames within a sequence. P = 1, PB = 2, PBB = 3, etc.

x264 [info]: mb I  I16..4: 18.3% 52.4% 29.2%
x264 [info]: mb P  I16..4:  3.6%  9.4%  3.0%  P16..4: 45.3% 18.5% 10.0%  0.0%  0.0%    skip:10.3%
x264 [info]: mb B  I16..4:  0.3%  1.0%  0.2%  B16..8: 35.2%  1.4%  1.6%  direct: 6.1%  skip:54.3%  L0:50.6% L1:43.0% BI: 6.3%

For each of the three macroblock types (I,P,B), show what percentage of partitions within are either I or the native type of partitions (which is P for P MBs and B for B MBs).

• The three numbers for I partitions represent 16x16, 8x8 and 4x4.
• For P partitions, the five numbers represent 16x16, 16x8/8x16, 8x8, 8x4/4x8 and 4x4.
• For B partitions, the three numbers represent 16x16, 16x8/8x16, 8x8.
• Skip shows the number of macroblocks using the skip vector (encoder doesnt write motion vector in bitstream, skips it) without residual, while Direct shows the number of MBs using the skip vector with a residual. Decoder derives motion vectors for direct/skip blocks by itself: taking into account near, already decoded blocks and averaging known, already estimated MVs.
• L0/L1 means references to past/future frames respectively.

x264 [info]: field mbs: intra: 0.0% inter:10.2% skip:3.0%

Printed when MBAFF used. Shows percent of macroblocks coded as fields.

x264 [info]: mb I  I16..4..PCM:, P I16..4..PCM:, mb B I16..4..PCM:

When encoder decide to use PCM macroblocks (raw uncompressed blocks of constant size) it prints table that looks same as for macroblock types, but blocknames with PCM prefix.

x264 [info]: final ratefactor: 27.45

Appears when doing an ABR pass, which indicates the average QP used for the encode

x264 [info]: 8x8 transform  intra:59.0%  inter:63.9%

x264 [info]: direct mvs  spatial:99.3%  temporal:0.7%

Percentage of frames using each method of direct/skip vector calculation. See above note about the skip vector.

x264 [info]: ref P L0  46.2% 18.9% 13.6%  7.7%  6.9%  6.6%
x264 [info]: ref B L0  51.2% 20.8% 13.7%  9.2%  5.2%
x264 [info]: ref B L1  84.7% 15.3%

Percentage of MBs (for each frame type) that use this many references. ref B L1 line appears when X264_Settings#b-pyramid is used and show usage of future B and P frames. Otherwise L1 always refs to next P-frame so no need to show it. L0/L1 ratio information printed above (in mb-B section).

x264 [info]: coded y,uvDC,uvAC intra: 39.9% 60.7% 56.2% inter: 29.3% 47.8% 37.6%

What percentage of blocks are coded as intra or inter, split between luma, chroma DC and chroma AC

x264 [info]: i16 v,h,dc,p: 47% 42%  8%  3%
x264 [info]: i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  3% 87%  7%  0%  0%  1%  0%  0%  1%
x264 [info]: i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 24% 27% 18%  6%  5%  5%  4%  5%  7%
x264 [info]: i8c dc,h,v,p: 33% 51% 12%  4%

i8c line appears only in cases when chroma resolution not match luma (output colorspace: yuv420, yuv422) Shows usage of each intra prediction modes, where:

• v - vertical
• h - horizontal
• dc - mean of corner pixels touching this macroblock
• ddl - diagonal down-left
• ddr - diagonal down-right
• vr - vertical-right
• hd - horizontal-down
• vl - vertical-left
• hu - horizontal-up
• p - plane

For detailed explanation see: H.264 intra predicion

x264 [info]: Weighted P-Frames: Y:5.2%

Percentage of weighted-p ref frames

x264 [info]: SSIM Mean Y:0.9851369 (17.254db)

When requesting SSIM calculations, the result is displayed and decibels.

x264 [info]: PSNR Mean Y:42.506 U:46.641 V:46.212 Avg:43.374 Global:42.523 

When requesting PSNR calculations, the result is displayed with final output bitrate (excluding container overhead)

x264 [info]: kb/s:237.1

The final output bitrate of x264, without container overhead, is displayed in this fashion when PSNR calculation is not requested.

encoded 300 frames, 119.24 fps, 722.37 kb/s

Is printed last to indicate the number of frames encoded, the average encoding rate, and the final bitrate (with container overhead).

This line is specific to the x264 CLI and is not displayed when using libx264.

When log-level set to debug x264 alse prints additional info per each frame/slice

x264 [debug]: frame=0 QP=31.40 NAL=3 Slice:I Poc:0   I:8160 P:0    SKIP:0 size=176884 bytes PSNR Y:47.26 U:48.93 V:48.83 SSIM Y:0.99550