mirror of https://github.com/mpv-player/mpv
171 lines
5.9 KiB
Plaintext
171 lines
5.9 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 1-31 (minimum quantizer) for pass1/2
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1 is not recommended (much larger file, little quality difference and
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possibly other weird things)
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2 is recommended for normal mpeg4/mpeg1video encoding
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3 is recommended for h263(p)/msmpeg4 (default)
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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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15 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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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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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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vb_qfactor (1.0-31.0) for pass1/2
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(B-Frame quantizer = IP-Frame quantizer * vb_qfactor)
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2.0 is default
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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 (only for 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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vqcomp (0.0-1.0) quantizer compression (for pass1/2)
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0.0 constant bitrate encoding, so fast motion frames will get as many
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bits as low motion (high motion scenes look bad)
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0.5 (default)
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1.0 constant quantizer encoding (low motion scenes look bad)
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vrc_strategy (0,1,2)
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FIXME (different rate control strategies)
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vlelim (0-1000) single coefficient elimination threshold for luminance
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0 disabled (default)
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4 (JVT recommendation)
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vcelim (0-1000) single coefficient elimination threshold for chrominance
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0 disabled (default)
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7 (JVT recommendation)
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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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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)
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0 (default)
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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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vbug manual workaround encoder bugs
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0 (default)
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1 (workaround for some old lavc generated msmpeg4v3 files)
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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 increase data partitioning or 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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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 vbug=1
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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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