From 7a424a473a6f1bc59b256d498caccc9a4943dd93 Mon Sep 17 00:00:00 2001 From: michael Date: Fri, 17 May 2002 11:50:23 +0000 Subject: lavc rate control tech-docs git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@6109 b3059339-0415-0410-9bf9-f77b7e298cf2 --- DOCS/tech/libavc-options.txt | 104 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 DOCS/tech/libavc-options.txt (limited to 'DOCS/tech') diff --git a/DOCS/tech/libavc-options.txt b/DOCS/tech/libavc-options.txt new file mode 100644 index 0000000000..ae8f2c89b0 --- /dev/null +++ b/DOCS/tech/libavc-options.txt @@ -0,0 +1,104 @@ +Description of what all thouse libavcodec options do ... +WARNING: iam no encoding expert so the recomanditions might be bad ... +if u find any errors, missing stuff, ... send a patch or cvs commit if u have an cvs account :) + +vqmin 1-31 (minimum quantizer) for pass1/2 + 1 is not recomanded (much larger file, little quality difference and possible other weird things) + 2 is recommanded for normal mpeg4/mpeg1video encoding + 3 is recommanded for h263(p)/msmpeg4 (default) + the reason for 3 instead of 2 is that 2 could lead to overflows (this will be fixed for h263(p) + by chageing 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 recomanded (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 + 15 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) + +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 or in lq mode currently + disabled by default + +keyint 0-300 (maximum interval between keyframes) + keyframes are needed for seeking as seeking is only possible to a keyframe but keyframes need more space + than non keyframes so larger numbers here mean slightly smaller files + 0 no keyframes + >300 is not recomanded as the quality might be bad (depends upon decoder & encoder & luck) + +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 missprediction) + +vpass + 1 first pass + 2 second pass + +vbitrate (kbits per sec) for pass1/2 + 800 is default + +vratetol (filesize tolerance in kbit) for pass1/2 + this is just approximate, the real difference can be much smaller or larger + 1000- 100000 is a sane range + 8000 is default + +vb_qfactor (1.0-31.0) (BFrame quantizer= PFrame quantizer * vb_qfactor) for pass1/2 + 2.0 is default + tip: to do constant quantizer encoding with different quantizers for I/P and B frames + u can use vqmin=:vqmax=:vb_qfactor= + +vqblur (0.0-1.0) quantizer blur (for 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 over time more so that the quantizer will be changed slower + +vqcomp (0.0-1.0) quantizer compression (for pass1/2) + 0.0 constant bitrate encoding, so fast moton frames will get as many bits as low motion + (high motion scenes look bad) + 0.5 (default) + 1.0 constant quantizer encoding (low motion scenes look bad) + +vrc_strategy (0,1,2) + FIXME + +Notes: 1. lavc will strictly follows 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: the file is much too small + A: vqmin=2 or 1 (be carefull with 1, it could cause strange things to happen) + Q: i want to use -pass 1 & -pass 2 with vmax_b_frames>0 + A: read DOCS/tech/patches.txt and send a patch ;) + +glossary: +MB Macroblock (16x16 luminance & 8x8 chrominance samples) +MV Motion vector +ME Motion estimation +MC Motion compensation + +example: +mencoder foobar.avi -lavcopts vcodec=mpeg4:vhq:keyint=300:vqscale=2 -o new-foobar.avi \ No newline at end of file -- cgit v1.2.3