Recherche avancée

Médias (91)

Autres articles (73)

  • Websites made ​​with MediaSPIP

    2 mai 2011, par

    This page lists some websites based on MediaSPIP.

  • Creating farms of unique websites

    13 avril 2011, par

    MediaSPIP platforms can be installed as a farm, with a single "core" hosted on a dedicated server and used by multiple websites.
    This allows (among other things) : implementation costs to be shared between several different projects / individuals rapid deployment of multiple unique sites creation of groups of like-minded sites, making it possible to browse media in a more controlled and selective environment than the major "open" (...)

  • Le profil des utilisateurs

    12 avril 2011, par

    Chaque utilisateur dispose d’une page de profil lui permettant de modifier ses informations personnelle. Dans le menu de haut de page par défaut, un élément de menu est automatiquement créé à l’initialisation de MediaSPIP, visible uniquement si le visiteur est identifié sur le site.
    L’utilisateur a accès à la modification de profil depuis sa page auteur, un lien dans la navigation "Modifier votre profil" est (...)

Sur d’autres sites (6919)

  • Further SMC Encoding Work

    25 août 2011, par Multimedia Mike — General

    Sometimes, when I don’t feel like doing anything else, I look at that Apple SMC video encoder again.

    8-bit Encoding
    When I last worked on the encoder, I couldn’t get the 8-color mode working correctly, even though the similar 2- and 4-color modes were working fine. I chalked the problem up to the extreme weirdness in the packing method unique to the 8-color mode. Remarkably, I had that logic correct the first time around. The real problem turned out to be with the 8-color cache and it was due to the vagaries of 64-bit math in C. Bit shifting an unsigned 8-bit quantity implicitly results in a signed 32-bit quantity, or so I discovered.

    Anyway, the 8-color encoding works correctly, thus shaving a few more bytes off the encoding size.

    Encoding Scheme Oddities
    The next step is to encode runs of data. This is where I noticed some algorithmic oddities in the scheme that I never really noticed before. There are 1-, 2-, 4-, 8-, and 16-color modes. Each mode allows encoding from 1-256 blocks of that same encoding. For example, the byte sequence :

      0x62 0x45

    Specifies that the next 3 4×4 blocks are encoded with single-color mode (of byte 0×62, high nibble is encoding mode and low nibble is count-1 blocks) and the palette color to be used is 0×45. Further, opcode 0×70 is the same except the following byte allows for specifying more than 16 (i.e., up to 256) blocks shall be encoded in the same matter. In light of this repeat functionality being built into the rendering opcodes, I’m puzzled by the existence of the repeat block opcodes. There are opcodes to repeat the prior block up to 256 times, and there are opcodes to repeat the prior pair of blocks up to 256 times.

    So my quandary is : What would the repeat opcodes be used for ? I hacked the FFmpeg / Libav SMC decoder to output a histogram of which opcodes are used. The repeat pair opcodes are never seen. However, the single-repeat opcodes are used a few times.

    Puzzle Solved ?
    I’m glad I wrote this post. Just as I was about to hit “Publish”, I think I figured it out. I haven’t mentioned the skip opcodes yet– there are opcodes that specify that 1-256 4×4 blocks are unchanged from the previous frame. Conceivably, a block could be unchanged from the previous frame and then repeated 1-256 times from there.

    That’s something I hadn’t thought of up to this point for my proposed algorithm and will require a little more work.

    Further reading

  • Merge commit ’d371c3c2e2830d9783465ecfe1ab7d93351083b7’

    17 mai 2013, par Michael Niedermayer
    Merge commit ’d371c3c2e2830d9783465ecfe1ab7d93351083b7’

    * commit ’d371c3c2e2830d9783465ecfe1ab7d93351083b7’ :
    
  vf_frei0r : make config_props work properly when called multiple times.
    
  vf_gradfun : make config_props work properly when called multiple times.
    
  vf_lut : make config_props work properly when called multiple times.
    

    Conflicts :
    
	libavfilter/vf_lut.c
    

    Merged-by : Michael Niedermayer <michaelni@gmx.at>
    • [DH] libavfilter/vf_frei0r.c
    • [DH] libavfilter/vf_gradfun.c
    • [DH] libavfilter/vf_lut.c

  • ffmpeg failing to convert

    27 mars 2014, par Daniel7912

    I am using the following command to convert a mp4 on my server to webm as part of a Node.js script.

    var command = execSync(&#39;ffmpeg -i &#39;+video+&#39; -vpre libvpx-720p -cpu-used -5 -deadline realtime -b 3900k -an -f webm -y &#39;+saveTo);

    When running the command in a regular terminal, it works fine. However, when running it as above using the execSync() node package, I get the following console output.

    Error: ffmpeg version 1.0.8 Copyright (c) 2000-2013 the FFmpeg developers
    
  built on Mar 27 2014 17:09:06 with gcc 4.7.3 (Gentoo 4.7.3-r1 p1.3, pie-0.5.5)
    
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared --cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-
    
g++ --ar=x86_64-pc-linux-gnu-ar --optflags=&#39;-O2 -pipe -march=native -fomit-frame-pointer&#39; --extra-cflags=&#39;-O2 -pipe -march=native -fomit-frame-pointer&#39; --extra-cxxflags
    
=&#39;-O2 -pipe -march=native -fomit-frame-pointer&#39; --disable-static --enable-gpl --enable-version3 --enable-postproc --enable-avfilter --enable-avresample --disable-stripp
    
ing --disable-debug --disable-doc --disable-vaapi --disable-vdpau --disable-ffplay --disable-runtime-cpudetect --enable-libmp3lame --enable-libvo-aacenc --enable-libthe
    
ora --enable-libfdk-aac --enable-nonfree --disable-indev=v4l2 --disable-indev=alsa --disable-indev=oss --disable-indev=jack --disable-outdev=alsa --disable-outdev=oss -
    
-disable-outdev=sdl --enable-libvorbis --enable-libvpx --disable-amd3dnow --disable-amd3dnowext --disable-altivec --disable-avx --disable-mmxext --disable-ssse3 --disab
    
le-vis --disabl  libavutil      51. 73.101 / 51. 73.101
    
  libavcodec     54. 59.100 / 54. 59.100
    
  libavformat    54. 29.104 / 54. 29.104
    
  libavdevice    54.  2.101 / 54.  2.101
    
  libavfilter     3. 17.100 /  3. 17.100
    
  libswscale      2.  1.101 /  2.  1.101
    
  libswresample   0. 15.100 /  0. 15.100
    
  libpostproc    52.  0.100 / 52.  0.100
    
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from &#39;/path/to/video/input.mp4&#39;:
    
  Metadata:
    
    major_brand     : mp42
    
    minor_version   : 0
    
    compatible_brands: mp42isomavc1
    
    creation_time   : 2013-08-24 21:58:35
    
    encoder         : HandBrake 0.9.9 2013051800
    
  Duration: 00:06:31.46, start: 0.000000, bitrate: 5092 kb/s
    
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 4919 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    
    Metadata:
    
      creation_time   : 2013-08-24 21:58:35
    
    Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, s16, 168 kb/s
    
    Metadata:
    
      creation_time   : 2013-08-24 21:58:35
    
Please use -b:a or -b:v, -b is ambiguous
    
[libvpx @ 0x7f0c40] v1.3.0
    
Output #0, webm, to &#39;/path/to/video/output.webm&#39;:
    
  Metadata:
    
    major_brand     : mp42
    
    minor_version   : 0
    
    compatible_brands: mp42isomavc1
    
    encoder         : Lavf54.29.104
    
    Stream #0:0(und): Video: vp8, yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=11-51, 3900 kb/s, 1k tbn, 25 tbc
    
    encoder         : Lavf54.29.104                                                                                                                          [4009/9202]
    
    Stream #0:0(und): Video: vp8, yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=11-51, 3900 kb/s, 1k tbn, 25 tbc
    
    Metadata:
    
      creation_time   : 2013-08-24 21:58:35
    
Stream mapping:
    
  Stream #0:0 -> #0:0 (h264 -> libvpx)
    
Press [q] to stop, [?] for help
    
[h264 @ 0x8f42a0] AVC: nal size 3235393
    
    Last message repeated 1 times
    
[h264 @ 0x8f42a0] no frame!
    
[h264 @ 0x7be7e0] concealing 7123 DC, 7123 AC, 7123 MV errors in P frame
    
[h264 @ 0x8f46c0] AVC: nal size 2572289
    
    Last message repeated 1 times
    
[h264 @ 0x8f46c0] no frame!
    
[h264 @ 0x8f4ae0] AVC: nal size 11559745
    
    Last message repeated 1 times
    
[h264 @ 0x8f4ae0] no frame!
    
[h264 @ 0x8f4f00] AVC: nal size 781975966
    
    Last message repeated 1 times
    
[h264 @ 0x8f4f00] no frame!
    
[h264 @ 0x7be7e0] AVC: nal size -1537130086
    
    Last message repeated 1 times
    
[h264 @ 0x7be7e0] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x8f42a0] AVC: nal size -1303101030
    
    Last message repeated 1 times
    
[h264 @ 0x8f42a0] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x8f46c0] AVC: nal size 833290655
    
    Last message repeated 1 times
    
[h264 @ 0x8f46c0] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x8f4ae0] AVC: nal size -816365157
    
    Last message repeated 1 times
    
[h264 @ 0x8f4ae0] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x8f4f00] AVC: nal size 776798623
    
    Last message repeated 1 times
    
[h264 @ 0x8f4f00] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x7be7e0] AVC: nal size -824622693
    
    Last message repeated 1 times
    
[h264 @ 0x7be7e0] no frame!
    
Error while decoding stream #0:0: Operation not permitted
    
[h264 @ 0x8f42a0] AVC: nal size 1276789151
    
Error while decoding stream #0:0: Operation not permitted
    
frame=    4 fps=0.0 q=0.0 Lsize=     107kB time=00:00:00.16 bitrate=5476.5kbits/s    
    
video:106kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.473334%
    
Received signal 2: terminating.

    The 'no frame' bits repeat several thousand times before it reaches the final section.

    Could someone tell me what's wrong ?

    Thanks for any help

Navigation