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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@7283 b3059339-0415-0410-9bf9-f77b7e298cf2
264 lines
9.4 KiB
Plaintext
264 lines
9.4 KiB
Plaintext
Description of what all those libavcodec options do ...
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WARNING: I am no encoding expert so the recommendations might be bad ...
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if you find any errors, missing stuff, ... send a patch or cvs commit if you
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have an cvs account :)
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lavcopts: (encoder options)
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---------------------------
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vqmin 2-31 (minimum quantizer) for pass1/2
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1 is not recommended (much larger file, little quality difference (if u are lucky)
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and other weird things (if u are less lucky))
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weird things: msmpeg4, h263 will be very low quality
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ratecontrol will be confused -> lower quality
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some decoders will not be able to decode it
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2 is recommended for normal mpeg4/mpeg1video encoding (default)
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3 is recommended for h263(p)/msmpeg4
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the reason for 3 instead of 2 is that 2 could lead to overflows
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(this will be fixed for h263(p) by changing the quanizer per MB in
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the future, but msmpeg4 doesnt support that so it cant be fixed for
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that)
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vqscale 1-31 quantizer for constant quantizer / constant quality encoding
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1 is not recommended (much larger file, little quality difference and
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possible other weird things)
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lower means better quality but larger files
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see vqmin
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vqmax 1-31 (maximum quantizer) for pass1/2
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31 default
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10-31 should be a sane range
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vqdiff 1-31 (maximum quantizer difference between I or P frames) for pass1/2
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3 default
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vmax_b_frames 0-4 (maximum number of B frames between non B frames)
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0 no b frames (default)
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0-2 is a sane range for mpeg4
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vme 0-5 (motion estimation)
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0 none (not recommanded, very lq)
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1 full (not recommanded, too slow)
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2 log (not recommanded, lq)
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3 phods (not recommanded, lq)
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4 EPZS (default)
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5 X1
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vhq (high quality mode)
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encode each MB as in all modes and choose the best (this is slow but
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better filesize/quality)
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disabled by default
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v4mv
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allow 4 MV per MB (little difference in filesize/quality)
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disabled by default
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cannot be used with B frames (should now work in lq mode)
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keyint 0-300 (maximum interval between keyframes)
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keyframes are needed for seeking as seeking is only possible to a
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keyframe but they need more space than non-keyframes so larger numbers here
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mean slightly smaller files, but less precise seeking
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0 no keyframes
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>300 is not recommended as the quality might be bad (depends upon
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decoder, encoder and luck)
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for strict mpeg1/2/4 compliance this would have to be <=132
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vb_strategy 0-1 for pass 2
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0 allways use the max number of B frames (default)
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1 avoid B frames in high motion scenes (this will cause bitrate
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misprediction)
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vpass
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1 first pass
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2 second pass
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(only need to specify if two-pass encoding is used)
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vbitrate (kbits per second) for pass1/2
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800 is default
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(if value is bigger then 16000 it is interpreted as bit not kbit!)
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vratetol (filesize tolerance in kbit) for pass1/2
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this is just an approximation, the real difference can be much smaller
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or larger
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1000-100000 is a sane range
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8000 is default
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vrc_maxrate (maximum bitrate in kbit/sec) for pass1/2
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vrc_minrate (minimum bitrate in kbit/sec) for pass1/2
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vrc_buf_size (buffer size in kbit) for pass1/2
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this is for stuff like VCD
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VCD: FIXME
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SVCD: ...
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DVD: ...
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Note: vratetol should not be too large during the 2.pass or there might
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be problems if vrc_(min|max)rate is used
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vb_qfactor (-31.0-31.0) for pass1/2
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1.25 is default
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vi_qfactor (-31.0-31.0) for pass1/2
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0.8 is default
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vb_qoffset (-31.0-31.0) for pass1/2
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1.25 is default
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vi_qoffset (-31.0-31.0) for pass1/2
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0.0 is default
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if v{b|i}_qfactor > 0
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I/B-Frame quantizer = P-Frame quantizer * v{b|i}_qfactor + v{b|i}_qoffset
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else
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do normal ratecontrol (dont lock to next P frame quantizer) and
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set q= -q * v{b|i}_qfactor + v{b|i}_qoffset
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tip: to do constant quantizer encoding with different quantizers for
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I/P and B frames you can use:
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vqmin=<ip_quant>:vqmax=<ip_quant>:vb_qfactor=<b_quant/ip_quant>
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vqblur (0.0-1.0) quantizer blur (pass1)
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0.0 qblur disabled
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0.5 is the default
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1.0 average the quantizer over all previous frames
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larger values will average the quantizer more over time so that it will
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be changed slower
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vqblur (0.0-99.0) quantizer blur (pass2)
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gaussian blur (gaussian blur cant be done during pass 1 as the future quantizers arent known)
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0.5 is the default
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larger values will average the quantizer more over time so that it will
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be changed slower
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vqcomp quantizer compression (for pass1/2)
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depends upon vrc_eq
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vrc_eq the main ratecontrol equation (for pass1/2)
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1 constant bitrate
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tex constant quality
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1+(tex/avgTex-1)*qComp approximately the equation of the old ratecontrol code
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tex^qComp with qcomp 0.5 or something like that (default)
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infix operators: +,-,*,/,^
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variables:
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tex texture complexity
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iTex,pTex intra, non intra texture complexity
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avgTex average texture complexity
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avgIITex average intra texture complexity in I frames
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avgPITex average intra texture complexity in P frames
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avgPPTex average non intra texture complexity in P frames
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avgBPTex average non intra texture complexity in B frames
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mv bits used for MVs
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fCode maximum length of MV in log2 scale
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iCount number of intra MBs / number of MBs
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var spatial complexity
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mcVar temporal complexity
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qComp qcomp from the command line
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isI, isP, isB is 1 if picture type is I/P/B else 0
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Pi,E see ur favorite math book
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functions:
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max(a,b),min(a,b) maximum / minimum
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gt(a,b) is 1 if a>b, 0 otherwise
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lt(a,b) is 1 if a<b, 0 otherwise
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eq(a,b) is 1 if a==b,0 otherwise
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sin,cos,tan,sinh,cosh,tanh,exp,log,abs
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vrc_override user specified quality for specific parts (ending credits ...) (for pass1/2)
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<start-frame>,<end-frame>,<quality>[/<start-frame>,<end-frame>,<quality>[/...]]
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quality 2..31 -> quantizer
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quality -500..0 -> quality correcture in %
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vrc_init_cplx (0-1000) initial complexity for pass1
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vqsquish (0 or 1) for pass1/2 how to keep the quantizer between qmin & qmax
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0 use cliping
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1 use a nice differentiable function (default)
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vlelim (-1000-1000) single coefficient elimination threshold for luminance
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0 disabled (default)
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-4 (JVT recommendation)
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negative values will allso consider the dc coefficient
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should be at least -4 or lower for encoding at quant=1
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vcelim (-1000-1000) single coefficient elimination threshold for chrominance
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0 disabled (default)
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7 (JVT recommendation)
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negative values will allso consider the dc coefficient
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should be at least -4 or lower for encoding at quant=1
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vstrict strict standard compliance
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only recommended if you want to feed the output into the mpeg4 reference
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decoder
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vdpart data partitioning
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adds 2 byte per video packet
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improves error-resistance when transfering over unreliable channels (eg.
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streaming over the internet)
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vpsize (0-10000) video packet size
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0 disabled (default)
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500-1000 good choice
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improves error-resistance (see vdpart for more info)
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gray grayscale only encoding (a bit faster than with color ...)
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vfdct (0-99) dct algorithm
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0 automatically select a good one (default)
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1 fast integer
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2 accurate integer
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3 mmx
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4 mlib
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lavdopts: (decoder options)
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---------------------------
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ver error resilience
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-1 needed for some very broken, encoders which completly ignore the
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standards (one M4S2 asf sample know to need this) (default)
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0
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1 more aggressive error detection, lavc might think that some correct
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streams contain errors
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bug manual workaround encoder bugs (cant be easily detected automatically)
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0 (default)
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1 for msmpeg4v3 workaround for some old lavc generated msmpeg4v3 files
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1 for mpeg4 workaround some opendivx? files
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see http://heroinewarrior.com for some samples
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2 for mpeg4 workaround xvid interlacing bug
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gray grayscale only decoding (a bit faster than with color ...)
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Notes: 1. lavc will strictly follow the quantizer limits vqmin, vqmax, vqdiff
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even if it violates the bitrate / bitrate tolerance
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2. changing some options between pass1 & 2 can reduce the quality
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FAQ: Q: Why is the filesize much too small?
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A: Try to increase vqmin=2 or 1 (be carefull with 1, it could cause
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strange things to happen).
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Q: Can I use -pass 1 & -pass 2 with vmax_b_frames>0 ?
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A: -pass x uses the divx4 twopass-encoding codem which is incompatible
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with the libavcodec encode.
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If you want to fix it read DOCS/tech/patches.txt and send a patch.
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Q: What provides better error recovery while keeping the filesize low?
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Should I use data partitioning or increase the number of video packets?
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A: Data partitioning is better in this case.
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Glossary:
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MB Macroblock (16x16 luminance and 8x8 chrominance samples)
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MV Motion vector
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ME Motion estimation
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MC Motion compensation
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RC Rate control
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DCT Discrete Cosine Transform
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IDCT Inverse Discrete Cosine Transform
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JVT Joint Video Team Standard -- http://www.itu.int/ITU-T/news/jvtpro.html
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Examples:
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mencoder foobar.avi -lavcopts vcodec=mpeg4:vhq:keyint=300:vqscale=2 -o new-foobar.avi
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mplayer foobar.avi -lavdopts bug=1
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Links:
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short intro to mpeg coding:
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http://www.eecs.umich.edu/~amarathe/mpeg.html
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longer intro to jpeg/mpeg coding:
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http://www.cs.sfu.ca/undergrad/CourseMaterials/CMPT479/material/notes/Chap4/Chap4.2/Chap4.2.html
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--
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Written 2002 by Michael Niedermayer and reviewed by Felix Buenemann.
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Check the MPlayer documentation for contact-addresses.
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