Alliance for Open Media Video Codec reference implementation (Mozilla branch)
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Yaowu Xu 88e24f07ae added code to clear 2nd order block when appropriate
It is discovered that in rare situations the 2nd order block may
produce a few small magnitude coefficients that has no effect on
reconstruction. The situations are a combination of low quantizer
values (high quality) and low energy in residual signals (content
dependent). This commit added code to detect such cases and reset
the 2nd order block to all 0.

Patch 1 to 4 used code to do all-zero-check on idct result buffer,
and tests on derf set showed a consistent gain of .12%-.14% on all
metrics.But due to a recent change Ie31d90b, the idct result buffer
is not longer populated. So patch 5&6 use an alternative method to
detect the situations. Tests on derf set now shows a consistent
quality gain of .16%-.20%.

As suggested by Jim, Patch 7&8 removed the condition of all first
order block not having any coefficient, instead we reset 2nd order
coefficients to all 0 if sum of absolute value of the coefficients
is small. So it does slightly more than just detecting the oddity
as discussed above, but tests on derf set now show a consistent
gain of .20%-.23% on all metrics.

It is worth noting here that this change does not have any effect
on mid/high quantizer range, it only affects the quantizer value
18 or blow. Within this range, the change helps compression by up
to 2.5% on clips in the derf set.

Change-Id: I718e19cf59a4fc2462cb7070832759beb9f7e7dd
2011-10-28 12:07:21 -07:00
build Add license text to configure generated files. 2011-10-20 16:37:02 -04:00
examples Added rate-targeted temporal scalability 2011-10-11 12:49:12 -07:00
libmkv Fix vpxenc encoding incorrect webm file header on big endian machines(Issue 331) 2011-07-12 14:49:57 -04:00
nestegg ivfdec: webm reader support 2010-10-25 22:01:40 -04:00
tools tools: author_first_release.sh 2011-08-19 15:44:45 -04:00
vp8 added code to clear 2nd order block when appropriate 2011-10-28 12:07:21 -07:00
vpx Bump ABI version number for temporal scalability 2011-10-11 12:57:17 -07:00
vpx_mem Replace vpx_ports/config.h with vpx_config.h 2011-09-22 13:33:54 +03:00
vpx_ports Replace vpx_ports/config.h with vpx_config.h 2011-09-22 13:33:54 +03:00
vpx_scale Fix incorrect pointer definition 2011-10-24 16:24:57 -07:00
.gitattributes Initial WebM release 2010-05-18 11:58:33 -04:00
.gitignore Added rate-targeted temporal scalability 2011-10-11 12:49:12 -07:00
.mailmap Update .mailmap entry for Ralph Giles 2011-08-02 10:09:36 -04:00
AUTHORS Update AUTHORS 2011-08-02 10:09:59 -04:00
CHANGELOG Update CHANGELOG for v0.9.7-p1 2011-08-15 17:02:45 -04:00
LICENSE LICENSE: update with latest text 2010-06-04 16:19:40 -04:00
PATENTS LICENSE: update with latest text 2010-06-04 16:19:40 -04:00
README purge wince configuration 2011-02-22 14:42:00 -05:00
args.c Add psnr/ssim tuning option 2010-12-17 10:01:05 -05:00
args.h Add psnr/ssim tuning option 2010-12-17 10:01:05 -05:00
configure Add license text to configure generated files. 2011-10-20 16:37:02 -04:00
docs.mk Remove examples.doxy dep w/--disable-examples 2011-02-24 15:11:05 -08:00
example_xma.c Use WebM in copyright notice for consistency 2010-09-09 10:01:21 -04:00
examples.mk Added rate-targeted temporal scalability 2011-10-11 12:49:12 -07:00
keywords.dox Initial WebM release 2010-05-18 11:58:33 -04:00
libs.doxy_template Use WebM in copyright notice for consistency 2010-09-09 10:01:21 -04:00
libs.mk Reduce grep match when generating offset files. 2011-09-20 15:36:44 -07:00
mainpage.dox documentation: minor cosmetics 2011-02-16 17:59:33 -08:00
md5_utils.c Adds "armvX-none-rvct" targets 2011-01-28 12:47:39 +02:00
md5_utils.h Use public domain implementation for MD5 algorithm 2010-06-14 08:48:22 -04:00
solution.mk obj_int_extract for Visual Studio 2011-03-10 18:49:54 -05:00
tools_common.c fix pipe support on windows 2010-11-02 09:14:24 -04:00
tools_common.h fix pipe support on windows 2010-11-02 09:14:24 -04:00
usage.dox documentation: minor cosmetics 2011-02-16 17:59:33 -08:00
usage_cx.dox Initial WebM release 2010-05-18 11:58:33 -04:00
usage_dx.dox Initial WebM release 2010-05-18 11:58:33 -04:00
vp8_api1_migration.txt Initial WebM release 2010-05-18 11:58:33 -04:00
vp8_scalable_patterns.c Added rate-targeted temporal scalability 2011-10-11 12:49:12 -07:00
vpxdec.c vpxdec updated to use !feof() instead of *buf_sz in readframe() 2011-09-22 15:03:28 -04:00
vpxenc.c vpxenc: fix rollover in status output 2011-10-18 17:34:10 -07:00
y4minput.c clean up unused variable warnings 2011-05-09 12:56:20 -04:00
y4minput.h Use WebM in copyright notice for consistency 2010-09-09 10:01:21 -04:00

README

vpx Multi-Format Codec SDK
README - 19 May 2010

Welcome to the WebM VP8 Codec SDK!

COMPILING THE APPLICATIONS/LIBRARIES:
  The build system used is similar to autotools. Building generally consists of
  "configuring" with your desired build options, then using GNU make to build
  the application.

  1. Prerequisites

    * All x86 targets require the Yasm[1] assembler be installed.
    * All Windows builds require that Cygwin[2] be installed.
    * Building the documentation requires PHP[3] and Doxygen[4]. If you do not
      have these packages, you must pass --disable-install-docs to the
      configure script.

    [1]: http://www.tortall.net/projects/yasm
    [2]: http://www.cygwin.com
    [3]: http://php.net
    [4]: http://www.doxygen.org

  2. Out-of-tree builds
  Out of tree builds are a supported method of building the application. For
  an out of tree build, the source tree is kept separate from the object
  files produced during compilation. For instance:

    $ mkdir build
    $ cd build
    $ ../libvpx/configure <options>
    $ make

  3. Configuration options
  The 'configure' script supports a number of options. The --help option can be
  used to get a list of supported options:
    $ ../libvpx/configure --help

  4. Cross development
  For cross development, the most notable option is the --target option. The
  most up-to-date list of supported targets can be found at the bottom of the
  --help output of the configure script. As of this writing, the list of
  available targets is:

    armv5te-linux-rvct
    armv5te-linux-gcc
    armv5te-symbian-gcc
    armv6-darwin-gcc
    armv6-linux-rvct
    armv6-linux-gcc
    armv6-symbian-gcc
    iwmmxt-linux-rvct
    iwmmxt-linux-gcc
    iwmmxt2-linux-rvct
    iwmmxt2-linux-gcc
    armv7-linux-rvct
    armv7-linux-gcc
    mips32-linux-gcc
    ppc32-darwin8-gcc
    ppc32-darwin9-gcc
    ppc64-darwin8-gcc
    ppc64-darwin9-gcc
    ppc64-linux-gcc
    x86-darwin8-gcc
    x86-darwin8-icc
    x86-darwin9-gcc
    x86-darwin9-icc
    x86-linux-gcc
    x86-linux-icc
    x86-solaris-gcc
    x86-win32-vs7
    x86-win32-vs8
    x86_64-darwin9-gcc
    x86_64-linux-gcc
    x86_64-solaris-gcc
    x86_64-win64-vs8
    universal-darwin8-gcc
    universal-darwin9-gcc
    generic-gnu

  The generic-gnu target, in conjunction with the CROSS environment variable,
  can be used to cross compile architectures that aren't explicitly listed, if
  the toolchain is a cross GNU (gcc/binutils) toolchain. Other POSIX toolchains
  will likely work as well. For instance, to build using the mipsel-linux-uclibc
  toolchain, the following command could be used (note, POSIX SH syntax, adapt
  to your shell as necessary):

    $ CROSS=mipsel-linux-uclibc- ../libvpx/configure

  In addition, the executables to be invoked can be overridden by specifying the
  environment variables: CC, AR, LD, AS, STRIP, NM. Additional flags can be
  passed to these executables with CFLAGS, LDFLAGS, and ASFLAGS.

  5. Configuration errors
  If the configuration step fails, the first step is to look in the error log.
  This defaults to config.err. This should give a good indication of what went
  wrong. If not, contact us for support.

SUPPORT
  This library is an open source project supported by its community. Please
  please email webm-users@webmproject.org for help.