From f5373be10ee16f04b11440be97c6c36cd9803f82 Mon Sep 17 00:00:00 2001 From: gpoirier Date: Sun, 27 Nov 2005 19:48:39 +0000 Subject: Add indicative QP for ASP and AVC codecs git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@17057 b3059339-0415-0410-9bf9-f77b7e298cf2 --- DOCS/xml/en/encoding-guide.xml | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/DOCS/xml/en/encoding-guide.xml b/DOCS/xml/en/encoding-guide.xml index e2ad01f228..53e4f1a268 100644 --- a/DOCS/xml/en/encoding-guide.xml +++ b/DOCS/xml/en/encoding-guide.xml @@ -1043,6 +1043,9 @@ Computing the resolution + The following steps will guide you to compute the resolution of your + encode without taking too much distortion by taking into account several + information about the souce video. First, you should compute the encoded aspect ratio: ARc = (Wc x (ARa / PRdvd )) / Hc @@ -1079,17 +1082,30 @@ - The CQ depends both on the bitrate and the movie resolution. + The CQ depends both on the bitrate, the video codec efficiency and the + movie resolution. In order to raise the CQ, typically you would downscale the movie given that the bitrate is computed in function of the target size and the length of the movie, which are constant. - A CQ below 0.18 usually ends up in a very blocky picture, because there + With MPEG-4 ASP codecs such as XviD + and libavcodec, a CQ below 0.18 + usually ends up in a pretty blocky picture, because there are not enough bits to code the information of each macroblock (MPEG4, like many other codecs, groups pixels by blocks of several pixels to compress the image; if there are not enough bits, the edges of those blocks are visible). It is therefore wise to take a CQ ranging from 0.20 to 0.22 for a 1 CD rip, - and 0.26-0.28 for 2 CDs. + and 0.26-0.28 for 2 CDs with standard encoding options. + More advanced encoding options such as those listed here for + libavcodec + and +XviD + should make it possible to get the same quality with CQ ranging from + 0.18 to 0.20 for 1 CD rip, and 0.24-0.26 for 2 CDs + With MPEG-4 ASP codecs such as x264, + you can use a CQ ranging from 0.14 to 0.16 with standard encoding options, + and should be able to go as low as 0.10 to 0.12 with + x264's advanced encoding settings. @@ -1098,6 +1114,8 @@ to a movie such as The Matrix, which contains many high-motion scenes. On the other hand, it is worthless to raise CQ higher than 0.30 as you would be wasting bits without any noticeable quality gain. + Also note that as said earlier on this quide, low resolution comparatively + need a bigger QP to look good. -- cgit v1.2.3