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• Dreamcast Serial Extractor

  31 décembre 2017, par Multimedia Mike — Sega Dreamcast

  It has not been a very productive year for blogging. But I started the year by describing an unfinished project that I developed for the Sega Dreamcast, so I may as well end the year the same way. The previous project was a media player. That initiative actually met with some amount of success and could have developed into something interesting if I had kept at it.

  By contrast, this post describes an effort that was ultimately a fool’s errand that I spent way too much time trying to make work.

  Problem Statement
  In my neverending quest to analyze the structure of video games while also hoarding a massive collection of them (though I’m proud to report that I did play at least a few of them this past year), I wanted to be able to extract the data from my many Dreamcast titles, both games and demo discs. I had a tool called the DC Coder’s Cable, a serial cable that enables communication between a Dreamcast and a PC. With the right software, you could dump an entire Dreamcast GD-ROM, which contained a gigabyte worth of sectors.

  Problem : The dumping software (named ‘dreamrip’ and written by noted game hacker BERO) operated in a very basic mode, methodically dumping sector after sector and sending it down the serial cable. This meant that it took about 28 hours to extract all the data on a single disc by running at the maximum speed of 115,200 bits/second, or about 11 kilobytes/second. I wanted to create a faster method.

  The Pitch
  I formed a mental model of dreamrip’s operation that looked like this :

  
  
  

  As an improvement, I envisioned this beautiful architecture :
  

  
  
  

  Architectural Assumptions
  My proposed architecture was predicated on the assumption that the disc reading and serial output functions were both I/O-bound operations and that the CPU would be idle much of the time. My big idea was to use that presumably idle CPU time to compress the sectors before sending them over the wire. As long as the CPU can compress the data faster than 11 kbytes/sec, it should be a win. In order to achieve this, I broke the main program into 3 threads :

  1. The first thread reads the sectors ; more specifically, it asks the drive firmware to please read the sectors and make the data available in system RAM
  2. The second thread waits for sector data to appear in memory and then compresses it
  3. The third thread takes the compressed data when it is ready and shuffles it out through the serial cable

  Simple and elegant, right ?

  For data track compression, I wanted to start with zlib in order to prove the architecture, but then also try bzip2 or lzma. As long as they could compress data faster than the serial port could write it, then it should be a win. For audio track compression, I wanted to use the Flake FLAC encoder. According to my notes, I did get both bzip2 compression and the Flake compressor working on the Dreamcast. I recall choosing Flake over the official FLAC encoder because it was much simpler and had fewer dependencies, always an important consideration for platforms such as this.

  Problems
  I worked for quite awhile on this project. I have a lot of notes recorded but a lot of the problems I had remain a bit vague in my memory. However, there was one problem I discovered that eventually sunk the entire initiative :

  The serial output operation is CPU-bound.

  My initial mental model was that the a buffer could be “handed off” to the serial subsystem and the CPU could go back to doing other work. Nope. Turns out that the CPU was participating at every step of the serial transfer.

  Further, I eventually dug into the serial driver code and learned that there was already some compression taking place via the miniLZO library.

  Lessons Learned

  • Recognize the assumptions that you’re making up front at the start of the project.
  • Prototype in order to ensure plausibility
  • Profile to make sure you’re optimizing the right thing (this is something I have learned again and again).

  Another interesting tidbit from my notes : it doesn’t matter how many sectors you read at a time, the overall speed is roughly the same. I endeavored to read 1000 2048-byte data sectors, 1 or 10 or 100 at a time, or all 1000 at once. My results :

  • 1 : 19442 ms
  • 10 : 19207 ms
  • 100 : 19194 ms
  • 1000 : 19320 ms

  No difference. That surprised me.

  Side Benefits
  At one point, I needed to understand how BERO’s dreamrip software was operating. I knew I used to have the source code but I could no longer find it. Instead, I decided to try to reverse engineer what I needed from the SH-4 binary image that I had. It wasn’t an ELF image ; rather, it was a raw binary meant to be loaded at a particular memory location which makes it extra challenging for ‘objdump’. This led to me asking my most viewed and upvoted question on Stack Overflow : “Disassembling A Flat Binary File Using objdump”. The next day, it also led me to post one of my most upvoted answers when I found the solution elsewhere.

  Strangely, I have since tried out the command line shown in my answer and have been unable to make it work. But people keep upvoting both the question and the answer.

  Eventually this all became moot when I discovered a misplaced copy of the source code on one of my computers.

  I strongly recall binging through the Alias TV show while I was slogging away on this project, so I guess that’s a positive association since I got so many fun screenshots out of it.

  The Final Resolution
  Strangely, I was still determined to make this project work even though the Dreamcast SD adapter arrived for me about halfway through the effort. Part of this was just stubbornness, but part of it was my assumptions about serial port speeds, in particular, my assumption that there was a certain speed-of-light type of limitation on serial port speeds so that the SD adapter, operating over the DC’s serial port, would not be appreciably faster than the serial cable.

  This turned out to be very incorrect. In fact, the SD adapter is capable of extracting an entire gigabyte disc image in 35-40 minutes. This is the method I have since been using to extract Dreamcast disc images.

  The post Dreamcast Serial Extractor first appeared on Breaking Eggs And Making Omelettes.

• What flags should enable to get maximum performance using ffpeg ?

  19 octobre 2017, par Sam

  I am using windows, my application is using opencv and for codecs, we have used ffmpeg. We see the performance is very slow, we want to improve it by compiling ffmpeg with all flags which could take hardware and GPU acceleation into consideration.
  I did ./configure --help inside the ffmpeg source, I see below list option, can you please tell which all can really imporve the performance. Note that we would like to take advantage of hardware and gpu capabilities.

      $ ./configure —help
  
      Usage : configure [options]
  
      Options : [defaults in brackets after descriptions]
      Help options :
  
        —help                   print this message
  
        —quiet                  Suppress showing informative output
  
        —list-decoders          show all available decoders
  
        —list-encoders          show all available encoders
  
        —list-hwaccels          show all available hardware accelerators
  
        —list-demuxers          show all available demuxers
  
        —list-muxers            show all available muxers
  
        —list-parsers           show all available parsers
  
        —list-protocols         show all available protocols
  
        —list-bsfs              show all available bitstream filters
  
        —list-indevs            show all available input devices
  
        —list-outdevs           show all available output devices
  
        —list-filters           show all available filters
      Standard options :
  
        —logfile=FILE           log tests and output to FILE [ffbuild/config.log]
  
        —disable-logging        do not log configure debug information
  
        —fatal-warnings         fail if any configure warning is generated
  
        —prefix=PREFIX          install in PREFIX [/usr/local]
  
        —bindir=DIR             install binaries in DIR [PREFIX/bin]
  
        —datadir=DIR            install data files in DIR [PREFIX/share/ffmpeg]
  
        —docdir=DIR             install documentation in DIR [PREFIX/share/doc/ffmpeg                                                                                                      ]
  
        —libdir=DIR             install libs in DIR [PREFIX/lib]
  
        —shlibdir=DIR           install shared libs in DIR [LIBDIR]
  
        —incdir=DIR             install includes in DIR [PREFIX/include]
  
        —mandir=DIR             install man page in DIR [PREFIX/share/man]
  
        —pkgconfigdir=DIR       install pkg-config files in DIR [LIBDIR/pkgconfig]
  
        —enable-rpath           use rpath to allow installing libraries in paths
  
                                 not part of the dynamic linker search path
  
                                 use rpath when linking programs (USE WITH CARE)
  
        —install-name-dir=DIR   Darwin directory name for installed targets
      Licensing options :
  
        —enable-gpl             allow use of GPL code, the resulting libs
  
                                 and binaries will be under GPL [no]
  
        —enable-version3        upgrade (L)GPL to version 3 [no]
  
        —enable-nonfree         allow use of nonfree code, the resulting libs
  
                                 and binaries will be unredistributable [no]
      Configuration options :
  
        —disable-static         do not build static libraries [no]
  
        —enable-shared          build shared libraries [no]
  
        —enable-small           optimize for size instead of speed
  
        —disable-runtime-cpudetect disable detecting CPU capabilities at runtime (sma                                                                                                      ller binary)
  
        —enable-gray            enable full grayscale support (slower color)
  
        —disable-swscale-alpha  disable alpha channel support in swscale
  
        —disable-all            disable building components, libraries and programs
  
        —disable-autodetect     disable automatically detected external libraries [no                                                                                                      ]
      Program options :
  
        —disable-programs       do not build command line programs
  
        —disable-ffmpeg         disable ffmpeg build
  
        —disable-ffplay         disable ffplay build
  
        —disable-ffprobe        disable ffprobe build
  
        —disable-ffserver       disable ffserver build
      Documentation options :
  
        —disable-doc            do not build documentation
  
        —disable-htmlpages      do not build HTML documentation pages
  
        —disable-manpages       do not build man documentation pages
  
        —disable-podpages       do not build POD documentation pages
  
        —disable-txtpages       do not build text documentation pages
      Component options :
  
        —disable-avdevice       disable libavdevice build
  
        —disable-avcodec        disable libavcodec build
  
        —disable-avformat       disable libavformat build
  
        —disable-swresample     disable libswresample build
  
        —disable-swscale        disable libswscale build
  
        —disable-postproc       disable libpostproc build
  
        —disable-avfilter       disable libavfilter build
  
        —enable-avresample      enable libavresample build [no]
  
        —disable-pthreads       disable pthreads [autodetect]
  
        —disable-w32threads     disable Win32 threads [autodetect]
  
        —disable-os2threads     disable OS/2 threads [autodetect]
  
        —disable-network        disable network support [no]
  
        —disable-dct            disable DCT code
  
        —disable-dwt            disable DWT code
  
        —disable-error-resilience disable error resilience code
  
        —disable-lsp            disable LSP code
  
        —disable-lzo            disable LZO decoder code
  
        —disable-mdct           disable MDCT code
  
        —disable-rdft           disable RDFT code
  
        —disable-fft            disable FFT code
  
        —disable-faan           disable floating point AAN (I)DCT code
  
        —disable-pixelutils     disable pixel utils in libavutil
      Individual component options :
  
        —disable-everything     disable all components listed below
  
        —disable-encoder=NAME   disable encoder NAME
  
        —enable-encoder=NAME    enable encoder NAME
  
        —disable-encoders       disable all encoders
  
        —disable-decoder=NAME   disable decoder NAME
  
        —enable-decoder=NAME    enable decoder NAME
  
        —disable-decoders       disable all decoders
  
        —disable-hwaccel=NAME   disable hwaccel NAME
  
        —enable-hwaccel=NAME    enable hwaccel NAME
  
        —disable-hwaccels       disable all hwaccels
  
        —disable-muxer=NAME     disable muxer NAME
  
        —enable-muxer=NAME      enable muxer NAME
  
        —disable-muxers         disable all muxers
  
        —disable-demuxer=NAME   disable demuxer NAME
  
        —enable-demuxer=NAME    enable demuxer NAME
  
        —disable-demuxers       disable all demuxers
  
        —enable-parser=NAME     enable parser NAME
  
        —disable-parser=NAME    disable parser NAME
  
        —disable-parsers        disable all parsers
  
        —enable-bsf=NAME        enable bitstream filter NAME
  
        —disable-bsf=NAME       disable bitstream filter NAME
  
        —disable-bsfs           disable all bitstream filters
  
        —enable-protocol=NAME   enable protocol NAME
  
        —disable-protocol=NAME  disable protocol NAME
  
        —disable-protocols      disable all protocols
  
        —enable-indev=NAME      enable input device NAME
  
        —disable-indev=NAME     disable input device NAME
  
        —disable-indevs         disable input devices
  
        —enable-outdev=NAME     enable output device NAME
  
        —disable-outdev=NAME    disable output device NAME
  
        —disable-outdevs        disable output devices
  
        —disable-devices        disable all devices
  
        —enable-filter=NAME     enable filter NAME
  
        —disable-filter=NAME    disable filter NAME
  
        —disable-filters        disable all filters
  
        —disable-v4l2_m2m       disable V4L2 mem2mem code [autodetect]
      External library support :
        Using any of the following switches will allow FFmpeg to link to the
  
        corresponding external library. All the components depending on that library
  
        will become enabled, if all their other dependencies are met and they are not
  
        explicitly disabled. E.g. —enable-libwavpack will enable linking to
  
        libwavpack and allow the libwavpack encoder to be built, unless it is
  
        specifically disabled with —disable-encoder=libwavpack.
        Note that only the system libraries are auto-detected. All the other external
  
        libraries must be explicitly enabled.
        Also note that the following help text describes the purpose of the libraries
  
        themselves, not all their features will necessarily be usable by FFmpeg.
        —disable-alsa           disable ALSA support [autodetect]
  
        —disable-appkit         disable Apple AppKit framework [autodetect]
  
        —disable-avfoundation   disable Apple AVFoundation framework [autodetect]
  
        —enable-avisynth        enable reading of AviSynth script files [no]
  
        —disable-bzlib          disable bzlib [autodetect]
  
        —disable-coreimage      disable Apple CoreImage framework [autodetect]
  
        —enable-chromaprint     enable audio fingerprinting with chromaprint [no]
  
        —enable-frei0r          enable frei0r video filtering [no]
  
        —enable-gcrypt          enable gcrypt, needed for rtmp(t)e support
  
                                 if openssl, librtmp or gmp is not used [no]
  
        —enable-gmp             enable gmp, needed for rtmp(t)e support
  
                                 if openssl or librtmp is not used [no]
  
        —enable-gnutls          enable gnutls, needed for https support
  
                                 if openssl is not used [no]
  
        —disable-iconv          disable iconv [autodetect]
  
        —disable-jack           disable libjack support [autodetect]
  
        —enable-jni             enable JNI support [no]
  
        —enable-ladspa          enable LADSPA audio filtering [no]
  
        —enable-libass          enable libass subtitles rendering,
  
                                 needed for subtitles and ass filter [no]
  
        —enable-libbluray       enable BluRay reading using libbluray [no]
  
        —enable-libbs2b         enable bs2b DSP library [no]
  
        —enable-libcaca         enable textual display using libcaca [no]
  
        —enable-libcelt         enable CELT decoding via libcelt [no]
  
        —enable-libcdio         enable audio CD grabbing with libcdio [no]
  
        —enable-libdc1394       enable IIDC-1394 grabbing using libdc1394
  
                                 and libraw1394 [no]
  
        —enable-libfdk-aac      enable AAC de/encoding via libfdk-aac [no]
  
        —enable-libflite        enable flite (voice synthesis) support via libflite [                                                                                                      no]
  
        —enable-libfontconfig   enable libfontconfig, useful for drawtext filter [no]
  
        —enable-libfreetype     enable libfreetype, needed for drawtext filter [no]
  
        —enable-libfribidi      enable libfribidi, improves drawtext filter [no]
  
        —enable-libgme          enable Game Music Emu via libgme [no]
  
        —enable-libgsm          enable GSM de/encoding via libgsm [no]
  
        —enable-libiec61883     enable iec61883 via libiec61883 [no]
  
        —enable-libilbc         enable iLBC de/encoding via libilbc [no]
  
        —enable-libkvazaar      enable HEVC encoding via libkvazaar [no]
  
        —enable-libmodplug      enable ModPlug via libmodplug [no]
  
        —enable-libmp3lame      enable MP3 encoding via libmp3lame [no]
  
        —enable-libopencore-amrnb enable AMR-NB de/encoding via libopencore-amrnb [no                                                                                                      ]
  
        —enable-libopencore-amrwb enable AMR-WB decoding via libopencore-amrwb [no]
  
        —enable-libopencv       enable video filtering via libopencv [no]
  
        —enable-libopenh264     enable H.264 encoding via OpenH264 [no]
  
        —enable-libopenjpeg     enable JPEG 2000 de/encoding via OpenJPEG [no]
  
        —enable-libopenmpt      enable decoding tracked files via libopenmpt [no]
  
        —enable-libopus         enable Opus de/encoding via libopus [no]
  
        —enable-libpulse        enable Pulseaudio input via libpulse [no]
  
        —enable-librsvg         enable SVG rasterization via librsvg [no]
  
        —enable-librubberband   enable rubberband needed for rubberband filter [no]
  
        —enable-librtmp         enable RTMP[E] support via librtmp [no]
  
        —enable-libshine        enable fixed-point MP3 encoding via libshine [no]
  
        —enable-libsmbclient    enable Samba protocol via libsmbclient [no]
  
        —enable-libsnappy       enable Snappy compression, needed for hap encoding [n                                                                                                      o]
  
        —enable-libsoxr         enable Include libsoxr resampling [no]
  
        —enable-libspeex        enable Speex de/encoding via libspeex [no]
  
        —enable-libssh          enable SFTP protocol via libssh [no]
  
        —enable-libtesseract    enable Tesseract, needed for ocr filter [no]
  
        —enable-libtheora       enable Theora encoding via libtheora [no]
  
        —enable-libtwolame      enable MP2 encoding via libtwolame [no]
  
        —enable-libv4l2         enable libv4l2/v4l-utils [no]
  
        —enable-libvidstab      enable video stabilization using vid.stab [no]
  
        —enable-libvmaf         enable vmaf filter via libvmaf [no]
  
        —enable-libvo-amrwbenc  enable AMR-WB encoding via libvo-amrwbenc [no]
  
        —enable-libvorbis       enable Vorbis en/decoding via libvorbis,
  
                                 native implementation exists [no]
  
        —enable-libvpx          enable VP8 and VP9 de/encoding via libvpx [no]
  
        —enable-libwavpack      enable wavpack encoding via libwavpack [no]
  
        —enable-libwebp         enable WebP encoding via libwebp [no]
  
        —enable-libx264         enable H.264 encoding via x264 [no]
  
        —enable-libx265         enable HEVC encoding via x265 [no]
  
        —enable-libxavs         enable AVS encoding via xavs [no]
  
        —enable-libxcb          enable X11 grabbing using XCB [autodetect]
  
        —enable-libxcb-shm      enable X11 grabbing shm communication [autodetect]
  
        —enable-libxcb-xfixes   enable X11 grabbing mouse rendering [autodetect]
  
        —enable-libxcb-shape    enable X11 grabbing shape rendering [autodetect]
  
        —enable-libxvid         enable Xvid encoding via xvidcore,
  
                                 native MPEG-4/Xvid encoder exists [no]
  
        —enable-libxml2         enable XML parsing using the C library libxml2 [no]
  
        —enable-libzimg         enable z.lib, needed for zscale filter [no]
  
        —enable-libzmq          enable message passing via libzmq [no]
  
        —enable-libzvbi         enable teletext support via libzvbi [no]
  
        —disable-lzma           disable lzma [autodetect]
  
        —enable-decklink        enable Blackmagic DeckLink I/O support [no]
  
        —enable-libndi_newtek   enable Newteck NDI I/O support [no]
  
        —enable-mediacodec      enable Android MediaCodec support [no]
  
        —enable-libmysofa       enable libmysofa, needed for sofalizer filter [no]
  
        —enable-openal          enable OpenAL 1.1 capture support [no]
  
        —enable-opencl          enable OpenCL code
  
        —enable-opengl          enable OpenGL rendering [no]
  
        —enable-openssl         enable openssl, needed for https support
  
                                 if gnutls is not used [no]
  
        —disable-sndio          disable sndio support [autodetect]
  
        —disable-schannel       disable SChannel SSP, needed for TLS support on
  
                                 Windows if openssl and gnutls are not used [autodetec                                                                                                      t]
  
        —disable-sdl2           disable sdl2 [autodetect]
  
        —disable-securetransport disable Secure Transport, needed for TLS support
  
                                 on OSX if openssl and gnutls are not used [autodetect                                                                                                      ]
  
        —disable-xlib           disable xlib [autodetect]
  
        —disable-zlib           disable zlib [autodetect]
        The following libraries provide various hardware acceleration features :
  
        —disable-audiotoolbox   disable Apple AudioToolbox code [autodetect]
  
        —disable-cuda           disable dynamically linked Nvidia CUDA code [autodete                                                                                                      ct]
  
        —enable-cuda-sdk        enable CUDA features that require the CUDA SDK [no]
  
        —disable-cuvid          disable Nvidia CUVID support [autodetect]
  
        —disable-d3d11va        disable Microsoft Direct3D 11 video acceleration code                                                                                                       [autodetect]
  
        —disable-dxva2          disable Microsoft DirectX 9 video acceleration code [                                                                                                      autodetect]
  
        —enable-libdrm          enable DRM code (Linux) [no]
  
        —enable-libmfx          enable Intel MediaSDK (AKA Quick Sync Video) code via                                                                                                       libmfx [no]
  
        —enable-libnpp          enable Nvidia Performance Primitives-based code [no]
  
        —enable-mmal            enable Broadcom Multi-Media Abstraction Layer (Raspbe                                                                                                      rry Pi) via MMAL [no]
  
        —disable-nvenc          disable Nvidia video encoding code [autodetect]
  
        —enable-omx             enable OpenMAX IL code [no]
  
        —enable-omx-rpi         enable OpenMAX IL code for Raspberry Pi [no]
  
        —enable-rkmpp           enable Rockchip Media Process Platform code [no]
  
        —disable-vaapi          disable Video Acceleration API (mainly Unix/Intel) co                                                                                                      de [autodetect]
  
        —disable-vda            disable Apple Video Decode Acceleration code [autodet                                                                                                      ect]
  
        —disable-vdpau          disable Nvidia Video Decode and Presentation API for                                                                                                       Unix code [autodetect]
  
        —disable-videotoolbox   disable VideoToolbox code [autodetect]
      Toolchain options :
  
        —arch=ARCH              select architecture []
  
        —cpu=CPU                select the minimum required CPU (affects
  
                                 instruction selection, may crash on older CPUs)
  
        —cross-prefix=PREFIX    use PREFIX for compilation tools []
  
        —progs-suffix=SUFFIX    program name suffix []
  
        —enable-cross-compile   assume a cross-compiler is used
  
        —sysroot=PATH           root of cross-build tree
  
        —sysinclude=PATH        location of cross-build system headers
  
        —target-os=OS           compiler targets OS []
  
        —target-exec=CMD        command to run executables on target
  
        —target-path=DIR        path to view of build directory on target
  
        —target-samples=DIR     path to samples directory on target
  
        —tempprefix=PATH        force fixed dir/prefix instead of mktemp for checks
  
        —toolchain=NAME         set tool defaults according to NAME
  
        —nm=NM                  use nm tool NM [nm -g]
  
        —ar=AR                  use archive tool AR [ar]
  
        —as=AS                  use assembler AS []
  
        —ln_s=LN_S              use symbolic link tool LN_S [ln -s -f]
  
        —strip=STRIP            use strip tool STRIP [strip]
  
        —windres=WINDRES        use windows resource compiler WINDRES [windres]
  
        —x86asmexe=EXE          use nasm-compatible assembler EXE [nasm]
  
        —cc=CC                  use C compiler CC [gcc]
  
        —cxx=CXX                use C compiler CXX [g++]
  
        —objcc=OCC              use ObjC compiler OCC [gcc]
  
        —dep-cc=DEPCC           use dependency generator DEPCC [gcc]
  
        —nvcc=NVCC              use Nvidia CUDA compiler NVCC [nvcc]
  
        —ld=LD                  use linker LD []
  
        —pkg-config=PKGCONFIG   use pkg-config tool PKGCONFIG [pkg-config]
  
        —pkg-config-flags=FLAGS pass additional flags to pkgconf []
  
        —ranlib=RANLIB          use ranlib RANLIB [ranlib]
  
        —doxygen=DOXYGEN        use DOXYGEN to generate API doc [doxygen]
  
        —host-cc=HOSTCC         use host C compiler HOSTCC
  
        —host-cflags=HCFLAGS    use HCFLAGS when compiling for host
  
        —host-cppflags=HCPPFLAGS use HCPPFLAGS when compiling for host
  
        —host-ld=HOSTLD         use host linker HOSTLD
  
        —host-ldflags=HLDFLAGS  use HLDFLAGS when linking for host
  
        —host-libs=HLIBS        use libs HLIBS when linking for host
  
        —host-os=OS             compiler host OS []
  
        —extra-cflags=ECFLAGS   add ECFLAGS to CFLAGS []
  
        —extra-cxxflags=ECFLAGS add ECFLAGS to CXXFLAGS []
  
        —extra-objcflags=FLAGS  add FLAGS to OBJCFLAGS []
  
        —extra-ldflags=ELDFLAGS add ELDFLAGS to LDFLAGS []
  
        —extra-ldexeflags=ELDFLAGS add ELDFLAGS to LDEXEFLAGS []
  
        —extra-ldlibflags=ELDFLAGS add ELDFLAGS to LDLIBFLAGS []
  
        —extra-libs=ELIBS       add ELIBS []
  
        —extra-version=STRING   version string suffix []
  
        —optflags=OPTFLAGS      override optimization-related compiler flags
  
        —nvccflags=NVCCFLAGS    override nvcc flags [-gencode arch=compute_30,code=sm                                                                                                      _30 -O2]
  
        —build-suffix=SUFFIX    library name suffix []
  
        —enable-pic             build position-independent code
  
        —enable-thumb           compile for Thumb instruction set
  
        —enable-lto             use link-time optimization
  
        —env="ENV=override"     override the environment variables
      Advanced options (experts only) :
  
        —malloc-prefix=PREFIX   prefix malloc and related names with PREFIX
  
        —custom-allocator=NAME  use a supported custom allocator
  
        —disable-symver         disable symbol versioning
  
        —enable-hardcoded-tables use hardcoded tables instead of runtime generation
  
        —disable-safe-bitstream-reader
  
                                 disable buffer boundary checking in bitreaders
  
                                 (faster, but may crash)
  
        —sws-max-filter-size=N  the max filter size swscale uses [256]
      Optimization options (experts only) :
  
        —disable-asm            disable all assembly optimizations
  
        —disable-altivec        disable AltiVec optimizations
  
        —disable-vsx            disable VSX optimizations
  
        —disable-power8         disable POWER8 optimizations
  
        —disable-amd3dnow       disable 3DNow ! optimizations
  
        —disable-amd3dnowext    disable 3DNow ! extended optimizations
  
        —disable-mmx            disable MMX optimizations
  
        —disable-mmxext         disable MMXEXT optimizations
  
        —disable-sse            disable SSE optimizations
  
        —disable-sse2           disable SSE2 optimizations
  
        —disable-sse3           disable SSE3 optimizations
  
        —disable-ssse3          disable SSSE3 optimizations
  
        —disable-sse4           disable SSE4 optimizations
  
        —disable-sse42          disable SSE4.2 optimizations
  
        —disable-avx            disable AVX optimizations
  
        —disable-xop            disable XOP optimizations
  
        —disable-fma3           disable FMA3 optimizations
  
        —disable-fma4           disable FMA4 optimizations
  
        —disable-avx2           disable AVX2 optimizations
  
        —disable-aesni          disable AESNI optimizations
  
        —disable-armv5te        disable armv5te optimizations
  
        —disable-armv6          disable armv6 optimizations
  
        —disable-armv6t2        disable armv6t2 optimizations
  
        —disable-vfp            disable VFP optimizations
  
        —disable-neon           disable NEON optimizations
  
        —disable-inline-asm     disable use of inline assembly
  
        —disable-x86asm         disable use of standalone x86 assembly
  
        —disable-mipsdsp        disable MIPS DSP ASE R1 optimizations
  
        —disable-mipsdspr2      disable MIPS DSP ASE R2 optimizations
  
        —disable-msa            disable MSA optimizations
  
        —disable-mipsfpu        disable floating point MIPS optimizations
  
        —disable-mmi            disable Loongson SIMD optimizations
  
        —disable-fast-unaligned consider unaligned accesses slow
      Developer options (useful when working on FFmpeg itself) :
  
        —disable-debug          disable debugging symbols
  
        —enable-debug=LEVEL     set the debug level []
  
        —disable-optimizations  disable compiler optimizations
  
        —enable-extra-warnings  enable more compiler warnings
  
        —disable-stripping      disable stripping of executables and shared libraries
  
        —assert-level=level     0(default), 1 or 2, amount of assertion testing,
  
                                 2 causes a slowdown at runtime.
  
        —enable-memory-poisoning fill heap uninitialized allocated space with arbitra                                                                                                      ry data
  
        —valgrind=VALGRIND      run "make fate" tests through valgrind to detect memo                                                                                                      ry
  
                                 leaks and errors, using the specified valgrind binary                                                                                                      .
  
                                 Cannot be combined with —target-exec
  
        —enable-ftrapv          Trap arithmetic overflows
  
        —samples=PATH           location of test samples for FATE, if not set use
  
                                 $FATE_SAMPLES at make invocation time.
  
        —enable-neon-clobber-test check NEON registers for clobbering (should be
  
                                 used only for debugging purposes)
  
        —enable-xmm-clobber-test check XMM registers for clobbering (Win64-only ;
  
                                 should be used only for debugging purposes)
  
        —enable-random          randomly enable/disable components
  
        —disable-random
  
        —enable-random=LIST     randomly enable/disable specific components or
  
        —disable-random=LIST    component groups. LIST is a comma-separated list
  
                                 of NAME[:PROB] entries where NAME is a component
  
                                 (group) and PROB the probability associated with
  
                                 NAME (default 0.5).
  
        —random-seed=VALUE      seed value for —enable/disable-random
  
        —disable-valgrind-backtrace do not print a backtrace under Valgrind
  
                                 (only applies to —disable-optimizations builds)
  
        —enable-osfuzz          Enable building fuzzer tool
  
        —libfuzzer=PATH         path to libfuzzer
  
        —ignore-tests=TESTS     comma-separated list (without "fate-" prefix
  
                                 in the name) of tests whose result is ignored
  
        —enable-linux-perf      enable Linux Performance Monitor API
      NOTE : Object files are built at the place where configure is launched.
  

• Curator of the Samples Archive

  13 mai 2011, par Multimedia Mike — General

  Remember how I mirrored the world-famous MPlayerHQ samples archive a few months ago ? Due to a series of events, the original archive is no longer online. However, me and the people who control the mplayerhq.hu domain figured out how to make samples.mplayerhq.hu point to samples.multimedia.cx.

  That means... I’m the current owner and curator of our central multimedia samples repository. Such power ! This should probably be the fulfillment of a decade-long dream for me, having managed swaths of the archive, most notably the game formats section.

  How This Came To Be

  If you pay any attention to the open source multimedia scene, you might have noticed that there has been a smidge of turmoil. Heated words were exchanged, authority was questioned, some people probably said some things they didn’t mean, and the upshot is that, where once there was one project (FFmpeg), there are now 2 projects (also Libav). And to everyone who has wanted me to mention it on my blog— there, I finally broke my silence and formally acknowledged the schism.

  For my part, I was just determined to ensure that the samples archive remained online, preferably at the original samples.mplayerhq.hu address. There are 10 years worth of web links out there pointing into the original repository.

  Better Solution

  I concede that it’s not entirely optimal to host the repository here at multimedia.cx. While I can offer a crazy amount of monthly bandwidth, I can’t offer rsync (invaluable for keeping mirrors in sync), nor can the server provide anonymous FTP or allow me to offer accounts to other admins who can manage the repository.

  The samples archive is also mirrored at samples.libav.org/samples. I understand that service is provided by VideoLAN. Right now, both repositories are known to be static. I’m open to brainstorms about how to improve the situation.