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