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471 lines
17 KiB
471 lines
17 KiB
Parts based on mplayers DOCS/tech/libavc-option.txt.
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Some (basic) options are supported through the transcode commandline and
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some through the config file ffmpeg.cfg or ~/.ffmpeg.cfg. The format of the
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config file is simple. It can consists of several sections, each prefixed
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by a header [codec] which is the same string you give to transcode through -F.
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WARNING: contrary to popular belief, it's NOT possible to supply libavcodec
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OPTIONS to the ffmpeg export module using -F. The -F option is solely used
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to select the CODEC. Libavcodec options go in the config file.
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To see all supported options, have a look at the output of 'transcode -y
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ffmpeg -F mpeg4 -q2'
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For the most up-to-date description of the options, have a look at your
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mplayer manual page. Note that not all options may be supported by transcode.
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--- ~/.ffmpeg.cfg ----
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[mpeg4]
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qpel = 1
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trellis = 1
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[mpeg1video]
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--- ~/.ffmpeg.cfg ----
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Now to the options.
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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 1-31 (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 quantizer 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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TRANSCODE: use --divx_quant min,max
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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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TRANSCODE: use --divx_quant min
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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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TRANSCODE: use --divx_quant min,max
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mbqmin 1-31 (minimum macroblock quantizer) for pass1/2
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2 default
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mbqmax 1-31 (maximum macroblock quantizer) for pass1/2
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31 default
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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 (experimantal, might change from time to time or be just broken)
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Note: 0-3 ignores the amount of bits spend currently, so dont complain
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about low quality
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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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enabled by default
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NOTE: this is option is obsolete and has been replaced by the mbd
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option, values:
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0: fast (real-time encoding) (default)
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1: hq mode 1
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2: hq mode 2
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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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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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TRANSCODE: use -w X,X,keyint
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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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Tip: u can try to use constant quantizer mode for pass1 (vqscale=<quantizer>)
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for huffyuv:
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pass 1 saves statistics
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pass 2 encodes with a optimal huffman table based upon the pass 1 stats
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TRANSCODE: use -R (1|2)
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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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TRANSCODE: use -w bitrate
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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 (-1,0,1) strict standard compliance
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0 (default)
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1 only recommended if you want to feed the output into the mpeg4 reference
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decoder
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-1 allows nonstandard YV12 huffyuv encoding (20% smaller files, but
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cant be played back by the official huffyuv codec)
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vdpart data partitioning
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adds 2 byte per video packet
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each videopacket will be encoded in 3 seperate partitions:
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1. MVs (=movement)
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2. DC coefficients (=low res picture)
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3. AC coefficients (=details)
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the MV & DC are most important, loosing them looks far worse than
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loosing the AC and the 1. & 2. partition (MV&DC) are far smaller than
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the 3. partition (AC) -> errors will hit the AC partition much more
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often than the MV&DC -> the picture will look better with partitioning
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than without, as without partitining an error will trash AC/DC/MV
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equally
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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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100-1000 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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idct (0-99) idct algorithm
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0 automatically select a good one (default)
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1 jpeg reference integer
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2 simple
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3 simplemmx
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4 libmpeg2mmx (inaccurate, DONT USE for encoding with keyint >100)
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5 ps2
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6 mlib
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7 arm
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note: all these IDCTs do pass the IEEE1180 tests AFAIK
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lumi_mask (0.0-1.0) luminance masking
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0.0 disabled (default)
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0.0-0.3 should be a sane range
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warning: be carefull, too large values can cause disasterous things
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warning2: large values might look good on some monitors but may look horrible
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on other monitors
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dark_mask (0.0-1.0) darkness masking
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0.0 disabled (default)
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0.0-0.3 should be a sane range
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warning: be carefull, too large values can cause disasterous things
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warning2: large values might look good on some monitors but may look horrible
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on other monitors / TV / TFT
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tcplx_mask (0.0-1.0) temporal complexity masking
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0.0 disabled (default)
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scplx_mask (0.0-1.0) spatial complexity masking
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0.0 disabled (default)
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0.0-0.5 should be a sane range
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larger values help against blockiness, if no deblocking filter is used
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for decoding
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Tip: crop any black borders completly away as they will reduce the quality
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of the MBs there, this is true if scplx_mask isnt used at all too
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naq normalize adaptive quantization (experimental)
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when using adaptive quantization (*_mask), the average per-MB quantizer
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may no longer match the requested frame-level quantizer. using naq will
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attempt to adjust the per-MB quantizers to maintain the proper average.
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ildct use interlaced dct
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format
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YV12 (default)
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422P (for huffyuv)
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pred (for huffyuv)
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0 left prediction
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1 plane/gradient prediction
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2 median prediction
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qpel use quarter pel motion compensation
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Tip: this seems only usefull for high bitrate encodings
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precmp comparission function for motion estimation pre pass
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cmp comparission function for full pel motion estimation
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subcmp comparission function for sub pel motion estimation
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mbcmp comparission function for macroblock decission
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0 SAD (sum of absolute differences) (default)
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1 SSE (sum of squared errors)
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2 SATD (sum of absolute hadamard transformed differences)
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3 DCT (sum of absolute dct transformed differences)
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4 PSNR (sum of the squared quantization errors) (dont use, low quality)
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5 BIT (number of bits needed for the block)
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6 RD (rate distoration optimal, slow)
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7 ZERO (0)
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+256 (use chroma too, doesnt work (correctly) with b frames currently)
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Tip: SAD is fast, SATD is good, SSE is something in between
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Tip2: when using SATD/DCT/BIT/RD for full pel search then a
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larger diamond something like dia=2 or dia=4 might improve
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quality, but only for some videos
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Note: mbcmp is only used if hq mode is disabled
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predia (-99 - 6) diamond type & size for motion estimation pre pass
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dia (-99 - 6) diamond type & size for motion estimation
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...
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-3 shape adaptive diamond with size 3
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-2 shape adaptive diamond with size 2
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-1 experimental
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1 normal size=1 diamond (default) =EPZS type diamond
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0
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000
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0
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2 normal size=2 diamond
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0
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000
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00000
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000
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0
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...
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Tip: the shape adaptive stuff seems to be faster at the same quality
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Note: the sizes of the normal diamonds and shape adaptive ones dont
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have the same meaning
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trell trellis quantization
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this will find the optimal encoding for each 8x8 block
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trellis quantization is quite simple a optimal quantization in the
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PSNR vs bitrate sense (assuming that there would be no rounding errors introduced
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by the IDCT, which is obviously not the case) it simply finds a block for the minimum of
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error + lambda*bits
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lambda is a qp dependant constant
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bits is the amount of bits needed to encode the block
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error is simple the sum of squared errors of the quantization
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last_pred (0-99) amount of motion predictors from the previous frame
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0 (default)
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a -> will use 2a+1 x 2a+1 MB square of MV predictors from the previous frame
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preme (0-2) Motion estimation pre-pass
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0 disabled
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1 only after I frames (default)
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2 allways
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subq (1-8) subpel refinement quality (for qpel)
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8 (default)
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Note: this has a significant effect on the speed
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psnr will print the psnr for the whole video after encoding and store the per frame psnr
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in a file with name like "psnr_012345.log"
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TRANSCODE: The decoder options are currently unused in transcode
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lavdopts: (decoder options)
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---------------------------
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ec error concealment
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1 use strong deblock filter for damaged MBs
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2 iterative MV search (slow)
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3 all (default)
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Note: just add the ones u want to enable
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er error resilience
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0 disabled
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1 carefull (should work with broken encoders)
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2 normal (default) (works with compliant encoders)
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3 agressive (more checks but might cause problems even for valid bitstreams)
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4 very agressive
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bug manual workaround encoder bugs (autodetection isnt foolproof for these)
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0 nothing
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1 autodetect bugs (default)
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2 for msmpeg4v3 some old lavc generated msmpeg4v3 files (no autodetect)
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4 for mpeg4 xvid interlacing bug (autodetected if fourcc==XVIX)
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8 for mpeg4 UMP4 (autodetected if fourcc==UMP4)
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16for mpeg4 padding bug
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32for mpeg4 illegal vlc bug (autodetected per fourcc)
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64for mpeg4 XVID&DIVX qpel bug (autodetected)
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Note: just add the ones u want to enable
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gray grayscale only decoding (a bit faster than with color ...)
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idct see lavcopts
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note: the decoding quality is highest if the same idct algorithm is used
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for decoding as for encoding, this is often not the most accurate though
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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: 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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DC The coefficient of the constant term in the DCT (avg value of block)
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JVT Joint Video Team Standard -- http://www.itu.int/ITU-T/news/jvtpro.html
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PSNR peak signal to noise ratio
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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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ftp://ftp.tek.com/mbd/manuals/video_audio/25W_11418_4.pdf
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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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