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• VP8 Codec Optimization Update

  16 juin 2010, par noreply@blogger.com (John Luther) — inside webm

  Since WebM launched in May, the team has been working hard to make the VP8 video codec faster. Our community members have contributed improvements, but there’s more work to be done in some interesting areas related to performance (more on those below).

  
  

  Encoder

  
  The VP8 encoder is ripe for speed optimizations. Scott LaVarnway’s efforts in writing an x86 assembly version of the quantizer will help in this goal significantly as the quantizer is called many times while the encoder makes decisions about how much detail from the image will be transmitted.

  For those of you eager to get involved, one piece of low-hanging fruit is writing a SIMD version of the ARNR temporal filtering code. Also, much of the assembly code only makes use of the SSE2 instruction set, and there surely are newer extensions that could be made use of. There are also redundant code removal and other general cleanup to be done ; (Yaowu Xu has submitted some changes for these).
  
  At a higher level, someone can explore some alternative motion search strategies in the encoder. Eventually the motion search can be decoupled entirely to allow motion fields to be calculated elsewhere (for example, on a graphics processor).
  

  Decoder

  
  Decoder optimizations can bring higher resolutions and smoother playback to less powerful hardware.

  Jeff Muizelaar has submitted some changes which combine the IDCT and summation with the predicted block into a single function, helping us avoid storing the intermediate result, thus reducing memory transfers and avoiding cache pollution. This changes the assembly code in a fundamental way, so we will need to sync the other platforms up or switch them to a generic C implementation and accept the performance regression. Johann Koenig is working on implementing this change for ARM processors, and we’ll merge these changes into the mainline soon.

  In addition, Tim Terriberry is attacking a different method of bounds checking on the "bool decoder." The bool decoder is performance-critical, as it is called several times for each bit in the input stream. The current code handles this check with a simple clamp in the innermost loops and a less-frequent copy into a circular buffer. This can be expensive at higher data rates. Tim’s patch removes the circular buffer, but uses a more complex clamp in the innermost loops. These inner loops have historically been troublesome on embedded platforms.
  
  To contribute in these efforts, I’ve started working on rewriting higher-level parts of the decoder. I believe there is an opportunity to improve performance by paying better attention to data locality and cache layout, and reducing memory bus traffic in general. Another area I plan to explore is improving utilization in the multi-threaded decoder by separating the bitstream decoding from the rest of the image reconstruction, using work units larger than a single macroblock, and not tying functionality to a specific thread. To get involved in these areas, subscribe to the codec-devel mailing list and provide feedback on the code as it’s written.
  

  Embedded Processors

  
  We want to optimize multiple platforms, not just desktops. Fritz Koenig has already started looking at the performance of VP8 on the Intel Atom platform. This platform need some attention as we wrote our current x86 assembly code with an out-of-order processor in mind. Since Atom is an in-order processor (much like the original Pentium), the instruction scheduling of all of the x86 assembly code needs to be reexamined. One option we’re looking at is scheduling the code for the Atom processor and seeing if that impacts the performance on other x86 platforms such as the Via C3 and AMD Geode. This is shaping up to be a lot of work, but doing it would provide us with an opportunity to tighten up our assembly code.
  
  These issues, along with wanting to make better use of the larger register file on x86_64, may reignite every assembly programmer’s (least ?) favorite debate : whether or not to use intrinsics. Yunqing Wang has been experimenting with this a bit, but initial results aren’t promising. If you have experience in dealing with a lot of assembly code across several similar-but-kinda-different platforms, these maintainability issues might be familiar to you. I hope you’ll share your thoughts and experiences on the codec-devel mailing list.
  
  Optimizing codecs is an iterative (some would say never-ending) process, so stay tuned for more posts on the progress we’re making, and by all means, start hacking yourself.
  
  It’s exciting to see that we’re starting to get substantial code contributions from developers outside of Google, and I look forward to more as WebM grows into a strong community effort.
  
  John Koleszar is a software engineer at Google.

  

• Gstreamer AAC encoding no more supported ?

  22 juillet 2016, par Gianks

  i’d like to include AAC as one of the compatible formats in my app but i’m having troubles with its encoding.
  FAAC seems to be missing in GStreamer-1.0 Debian-derived packages (see Ubuntu) and the main reason for that (if i got it correctly) is the presence of avenc_aac (Lunchpad bugreport) as a replacement.

  I’ve tried the following :

  gst-launch-1.0 filesrc location="src.avi" ! tee name=t  t.! queue ! decodebin ! progressreport ! x264enc ! mux. t.! queue ! decodebin ! audioconvert ! audioresample ! avenc_aac compliance=-2 ! mux. avmux_mpegts name=mux ! filesink location=/tmp/test.avi

  It hangs prerolling with :

  ERROR libav :0:: AAC bitstream not in ADTS format and extradata missing

  Using mpegtsmux instead of avmux_mpegts seems to work since the file is created but it results with no working audio (with some players it’s completely unplayable).

  This is the trace of mplayer :

  Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
  
  [aac @ 0x7f2860d6c3c0]channel element 3.15 is not allocated
  
  [aac @ 0x7f2860d6c3c0]Sample rate index in program config element does not match the sample rate index configured by the container.
  
  [aac @ 0x7f2860d6c3c0]Inconsistent channel configuration.
  
  [aac @ 0x7f2860d6c3c0]get_buffer() failed
  
  [aac @ 0x7f2860d6c3c0]Assuming an incorrectly encoded 7.1 channel layout instead of a spec-compliant 7.1(wide) layout, use -strict 1 to decode according to the specification instead.
  
  [aac @ 0x7f2860d6c3c0]Reserved bit set.
  
  [aac @ 0x7f2860d6c3c0]Number of bands (20) exceeds limit (14).
  
  [aac @ 0x7f2860d6c3c0]invalid band type
  
  [aac @ 0x7f2860d6c3c0]More than one AAC RDB per ADTS frame is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
  
  [aac @ 0x7f2860d6c3c0]Reserved bit set.
  
  [aac @ 0x7f2860d6c3c0]Number of bands (45) exceeds limit (28).
  
  Unknown/missing audio format -> no sound
  
  ADecoder init failed :(
  
  Opening audio decoder: [faad] AAC (MPEG2/4 Advanced Audio Coding)
  
  FAAD: compressed input bitrate missing, assuming 128kbit/s!
  
  AUDIO: 44100 Hz, 2 ch, floatle, 128.0 kbit/9.07% (ratio: 16000->176400)
  
  Selected audio codec: [faad] afm: faad (FAAD AAC (MPEG-2/MPEG-4 Audio))
  
  ==========================================================================
  
  AO: [pulse] 44100Hz 2ch floatle (4 bytes per sample)
  
  Starting playback...
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Channel coupling not yet implemented, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: Failed to decode frame: Bitstream value not allowed by specification 
  
  Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
  
  VO: [vdpau] 640x480 => 640x480 Planar YV12 
  
  A:3602.2 V:3600.0 A-V:  2.143 ct:  0.000   3/  3 ??% ??% ??,?% 0 0 
  
  FAAD: error: Array index out of range, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Unexpected fill element with SBR data, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Bitstream value not allowed by specification, trying to resync!
  
  FAAD: error: Channel coupling not yet implemented, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: error: PCE shall be the first element in a frame, trying to resync!
  
  FAAD: error: Invalid number of channels, trying to resync!
  
  FAAD: Failed to decode frame: Invalid number of channels 
  
  A:3602.2 V:3600.1 A-V:  2.063 ct:  0.000   4/  4 ??% ??% ??,?% 0 0 

  These the messages produced by VLC (10 seconds of playback) :

  ts info: MPEG-4 descriptor not found for pid 0x42 type 0xf
  
  core error: option sub-original-fps does not exist
  
  subtitle warning: failed to recognize subtitle type
  
  core error: no suitable demux module for `file/subtitle:///tmp//test.avi.idx'
  
  avcodec info: Using NVIDIA VDPAU Driver Shared Library 361.42 Tue Mar 22 17:29:16 PDT 2016 for hardware decoding.
  
  core warning: VoutDisplayEvent 'pictures invalid'
  
  core warning: VoutDisplayEvent 'pictures invalid'
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio warning: ADTS CRC not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: ADTS CRC not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio warning: Invalid ADTS header
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported
  
  packetizer_mpeg4audio error: Multiple blocks per frame in ADTS not supported

  Using the error of the hanging pipeline I’ve finally discovered that avenc_aac should be told in such way to output the data NOT in RAW AAC but in ADTS AAC, the point is that i’ve no idea how to do that with Gstreamer. See here, bottom of the page : FFMPEG Ticket

  At this point since i’ve found no documentation seems right to say we have no support for AAC encoding in GStreamer... which isn’t true, i guess ! (IMHO anyway seems strange the missing of FAAC if AVENC_AAC requires all the time to be set in experimental mode)

  Can someone propose a working pipeline for this ?

  UPDATE

  After some more research i’ve found (via gst-inspect on avenc_aac) what i’m probably looking for but i don’t know how to setup it as needed.
  Have a look at stream-format :

  Pad Templates:
  
    SRC template: 'src'
  
      Availability: Always
  
      Capabilities:
  
        audio/mpeg
  
                 channels: [ 1, 6 ]
  
                     rate: [ 4000, 96000 ]
  
              mpegversion: 4
  
            stream-format: raw
  
          base-profile: lc

  Thanks

• Piwik 3 Development Update #1 – New UI design, API changes & release date

  1er septembre 2016, par Thomas Steur — Community, Development

  Over the last months, we have been actively working on the Piwik 3 release and we want to introduce you to the changes that we have done so far. They include a new and modern UI redesign, new widgets for your dashboard, and technical improvements under the hood.

  New Piwik 3 UI

  Based on Material Design we have revamped the user interface which is now more responsive, more usable and faster. While the UI is not yet finished, we invite you to check it out already and to let us know what you think.

  

  This new Piwik material design is a visual language that synthesizes classic principles of good design with the innovation and possibility of technology and science.

  More responsive

  Piwik 3 will look and feel much better on your mobile phone and tablet. Many elements have been improved : the menus, the segment editor and dashboard selector, the widgets, the settings pages and most other pages so you can fully experience and enjoy Piwik on any device !

  

  Improved usability

  We have updated the menu structure, the dashboard selector as well as the footer in reports to make your life easier when using Piwik. We love to keep these complicated things simple. There are also many other tiny improvements that you will appreciate.

  

  The Zen Mode lets you view in full screen your analytics reports and dashboards. Users love this feature and it can now be accessed by pressing “z” key.

  

  Faster

  To make the Piwik interface faster, we have refactored most of our CSS, HTML and JavaScript and moved more and more of our code into the client. As a result, Piwik now needs to reload the page much less often ! For example when you change the date or change the segment, Piwik will now load the reports instantly. To improve performance even further, Piwik will now load multiple reports on a single page in parallel.

  Native fonts

  Over the last months more and more web services have started using system fonts, and so will Piwik 3. System fonts look better, improve language support and give you a more native, familiar feeling.

  For more details and screenshots have a look at the pull request for the Piwik 3 UI update.

  New widgets

  With the “Latest Piwik Plugin Updates” widget you won’t miss any newly added or updated plugin anymore. This will help you learn about and discover the useful plugins and themes available on the Marketplace.

  

  Super users can now see at a glance the current state of the Piwik system, thanks to the new “System Check” and “System Summary” widgets.

  

  API Changes

  Piwik is the leading open analytics platform, highly customisable and extensible thanks to a flexible plugins architecture and a design based on APIs. In this new major Piwik 3 release, we significantly improve the foundation of our open platform and several of its core APIs.

  The new Widgets and Reporting API makes it possible to add reports and widgets to any existing reporting page. In the past, reporting pages had to be created manually which was time consuming and it was hard to maintain a consistent look across different reporting pages. Now reporting pages are generated automatically by the Piwik platform.

  The Plugin Settings API was changed to improve performance and to let plugin developers customize the Websites Manager. This is one step towards our goal to let users not only manage websites but also mobile apps, cars, coffee machines or any other thing.

  To see a full list of changes in the Piwik 3 analytics platform, have a look at the developer changelog.

  Developer docs

  The Piwik Developer Zone is full of guides and API references to help developers understand, integrate and extend Piwik. As some APIs have changed in the Piwik 3 release it is now possible to select the Piwik version in the top right corner of the developer zone.

  

  We are updating guides for Piwik 3 and added a Piwik 2 -> Piwik 3 Migration Guide for plugin developers. Many other guides were updated such as Menus, Custom Report and Widgets.

  Release date

  The first Piwik 3 beta release will be available in the next four weeks. Beta testers automatically receive the update if they are subscribed to the “Latest Beta” release channel. The final Piwik 3 release will be ready before the end of the year. If you want to give it a try, you can either use Piwik from Git and check out the “3.x-dev” branch, or download Piwik 3 from GitHub.

  Closing thoughts

  With faster & more beautiful reports, better APIs and more stability, Piwik 3 is a big step forward for all Piwik users. As our mission is to create, as a community, the leading international open source web analytics platform that gives every user full control of their data, we are very excited to introduce you to this upcoming release.

  We now offer Custom Development services if you like to sponsor a new feature or bug fix, or if you have any custom requirements. And if you use Piwik Analytics to grow your business and need quality help, contact the Piwik analytics experts to get started.

  Until our next Piwik 3 dev update, Happy analysis !