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• Losslessly encode png frames to webm with ffmpeg

  18 juillet 2017, par Peaser

  I need to convert a directory of frames to webm with absolutely no image compression, just raw images-to-frames. Using ffmpeg version N-82889-g54931fd, this is what I’m at right now.

  ffmpeg -framerate 30 -f image2 -i frames/%02d.png -pix_fmt yuva420p -crf 0 output.webm

  The crf 0 flag was told to be the answer, but the output is still full of compression and artifacts. Is there an option to make each frame as close to identical as possible to their corresponding png image frame ?

• Piwik Analytics and becoming a Piwik Certified Professional

  10 juillet 2017, par Piwik Core Team — About

  Digital Analytics software

  Piwik Analytics is the leading open source digital analytics software, offering users around the world an opportunity to liberate their analytics. Most recently, they have introduced the Piwik Certified Professional certification exam which now allows users to become qualified in Piwik Analytics software on an individual level to gain a deeper understanding of Piwik. In this blog post I will guide you through the topics that are covered during the exam and provide you with advice on taking the official Piwik Certified Professional exam.

  

  Piwik certification exam

  Taking the exam will cost you a maximum investment of 60 minutes of your time, besides learning all materials of course. The exam consists of 55 multiple choice questions with four answers to choose from. The score needed to pass is 80% (44 questions answered correctly) and the cost is 50 USD total. An earned certificate is valid for 18 months, before these eighteen months are over a person should pass the exam again in order to retain the certified status.

  Learning topics

  The exam consists of two sections. The main section is focused on the Piwik Analytics software itself while the second part relates to digital analytics in general. All topics and content covered about Piwik Analytics is available through the official Piwik user guides. The second section tests your experience as a digital analyst, online marketer or any other function title in which you work with Piwik Analytics. In this case, the general digital analytics questions should be quite straightforward and easy to answer, and cover only a fraction of the total questions in the exam (around 10% with 5-7 general questions). An outline of all exam topics are listed below :

  • A Tour of Piwik
  • Track Goals and Measure Conversions
  • Event Tracking
  • Content Tracking
  • Ecommerce Analytics
  • Row Evolution – View and compare historical data
  • Segmentation – Compare segments of visitors
  • Visitors Maps – World, region, city
  • Real Time Visitor World Map
  • Real Time Analytics
  • The Visitor Profile
  • Site speed and Page speed
  • Site Search Tracking and Reporting
    
  • Transitions – Analyze the previous and following actions of your visitors for each page
  • Page Overlay
  • Custom Variables Analytics
  • Custom Dimensions
  • User ID
  • Annotating your data
  • Tracking Campaigns
  • URL Builder for Marketing Campaign Tracking

  The best way to prepare for the exam is read the entire Piwik user guides. You should definitely read the “Analytics Features” section since most questions of the Piwik Certified Professional – Digital Analytics exam that will be asked come from these sections. Furthermore you should be able to find your way around in Piwik at a basic level which means you know what the reports mean and where to find certain information. In addition, some basic knowledge regarding the settings is useful too. The exam is definitely not a technical implementation exam so no coding knowledge or any other deeply technical knowledge regarding Piwik is required.

  Finally, some general questions will be asked regarding digital analytics covering topics about KPI’s and the role of the analyst within an organization. While Piwik provides some links to articles by Avinash Kaushik covering these topics, you will not be able to learn these topics just by reading. When you have some experience with digital analytics you should be able to answer these general digital analytics questions with common sense and (even basic) experience as a digital analyst, analytics consultant, online marketer or any other related job whereby you work with Piwik.

  Taking the exam

  With 55 questions to be answered in 60 minutes the key to passing the exam is to keep moving. You have about 1 minute and 5 seconds to answer each question. This means that you should focus on the easiest questions first and return later to the questions that are a bit more challenging to answer. Keep an eye on the timer that will be displayed in the exam window. When the time expires or you click ‘Finish test’ your exam will end and be automatically submitted for review. Remember to first check all questions and answers before you click on the ‘Finish test’ button. If you click too soon and you still haven’t answered all questions, all unanswered questions will be marked as incorrect.

  During the test, no hard copy or online materials may be referenced. As you can imagine, it is almost impossible to check if users reference these kind of materials. However, be aware of the penalty system that is in place during the test. When a user leaves from the active test screen to another screen (i.e. a different browser tab) the screen turns red and provides a warning count when the user returns to the test screen again. You will have three warnings, after this your test will be submitted and graded as false. Furthermore, keep in mind you will have to do the test in one go and cannot pause and come back another time.

  Practice makes perfect

  Below I have included some example questions that could be asked during the exam. These questions do not necessarily represent how Piwik will test you on these topics.

  • What is the default report date that is selected by Piwik ?
  • Why would someone flatten a report in Piwik ?
  • Why would a user especially use the Page Overlay report ?
  • What are the three main Ecommerce interactions tracked with Piwik ?
  • What is an example of an anonymized IP address in Piwik ?

  Passing the Piwik Certified Professional – Digital Analytics exam

  Directly after submitting the exam you will receive a notification telling you whether or not you have passed the exam. If you pass, you will be able to download your personal certification right away. A report of your exam performance will also be available. This report lists the amount of correct answers and total questions by topic. The report with your exam performance is also available if you did not pass the exam. The certificate is valid for 18 months from the date of successful completion.

  Sometimes the difference between passing and failing can be a matter of how you interpret some of Piwik’s questions. There are several tricky questions included, so be sure to pay attention to detail on every question. If you fail, you may take the exam again. You will have to pay the 50 USD fee for each try, so do your best to pass it the first time.

  → Register to become a Piwik Certified Professional.

  We wish you the best of luck and happy analytics !

• FFMpeg is slow on Android [duplicate]

  28 juin 2017, par Oleg Filimonov

  This question already has an answer here :

  • Precompiled FFmpeg for android versus building FFmpeg using android NDK
    
    2 answers
    
  • Fast Video Compression on Android
    
    2 answers
    

  I’m using this library : https://github.com/WritingMinds/ffmpeg-android

  Executing this command :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast out.mp4

  (Basically add a bunch of animated overlays to the video)

  On PC this command takes about a second to execute (render speed is about 278 fps). But on Android device with Snapdragon 821 it takes about 10 seconds (about 30 fps).

  The curious thing is that whenever command is executing on PC, CPU load is around 90%, but on Android it’s less than 1% (see screenshot : initial spike is UI stuff plus loading binaries, afterwards ffmpeg was executing until 10 second mark)

  

  I tried executing the same command, but writing to /dev/null
  instead of the file :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast -f null /dev/null

  This reduced time by 3 seconds.

  I also tried replacing gif overlay with png overlay, but speed didn’t improve significantly.

  Here’s log of the command execution on Android :

  ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (GCC)
  
    configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/data/user/0/com.example.user.proofofconcept/files/in_10s.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 2017-06-27 18:07:54
  
    Duration: 00:00:10.47, start: 0.000000, bitrate: 14043 kb/s
  
      Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1280x720, 13971 kb/s, 29.86 fps, 30.01 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:53
  
        handler_name    : VideoHandle
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:54
  
        handler_name    : SoundHandle
  
  Input #1, gif, from '/data/user/0/com.example.user.proofofconcept/files/overlay.gif':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Video: gif, bgra, 130x98, 6.17 fps, 4.92 tbr, 100 tbn, 100 tbc
  
  [swscaler @ 0xeddb3000] deprecated pixel format used, make sure you did set range correctly
  
  [libx264 @ 0xee1fdc00] using cpu capabilities: none!
  
  [libx264 @ 0xee1fdc00] profile Constrained Baseline, level 3.2
  
  [libx264 @ 0xee1fdc00] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  Output #0, mp4, to '/storage/emulated/0/temp/out.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 30.01 fps, 90k tbn, 30.01 tbc (default)
  
      Metadata:
  
        encoder         : Lavc57.24.102 libx264
  
      Side data:
  
        unknown side data type 10 (24 bytes)
  
  Stream mapping:
  
    Stream #0:0 (h264) -> overlay:main
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    overlay -> Stream #0:0 (libx264)
  
  Press [q] to stop, [?] for help
  
  frame=   16 fps=0.0 q=24.0 size=     227kB time=00:00:00.29 bitrate=6210.2kbits/s dup=2 drop=0 speed=0.56x    
  
  frame=   29 fps= 28 q=24.0 size=     451kB time=00:00:00.73 bitrate=5042.1kbits/s dup=2 drop=0 speed=0.707x    
  
  frame=   40 fps= 26 q=24.0 size=     637kB time=00:00:01.09 bitrate=4744.5kbits/s dup=2 drop=0 speed=0.71x    
  
  frame=   57 fps= 28 q=24.0 size=     903kB time=00:00:01.66 bitrate=4441.3kbits/s dup=2 drop=0 speed=0.812x    
  
  frame=   75 fps= 29 q=24.0 size=    1186kB time=00:00:02.26 bitrate=4288.0kbits/s dup=2 drop=0 speed=0.885x    
  
  frame=   94 fps= 31 q=24.0 size=    1456kB time=00:00:02.89 bitrate=4113.4kbits/s dup=2 drop=0 speed=0.945x    
  
  frame=  113 fps= 32 q=25.0 size=    1780kB time=00:00:03.53 bitrate=4127.3kbits/s dup=2 drop=0 speed=0.985x    
  
  frame=  131 fps= 32 q=24.0 size=    2101kB time=00:00:04.13 bitrate=4165.9kbits/s dup=2 drop=0 speed=1.01x    
  
  frame=  150 fps= 33 q=24.0 size=    2461kB time=00:00:04.76 bitrate=4231.2kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  165 fps= 32 q=24.0 size=    2721kB time=00:00:05.26 bitrate=4234.1kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  185 fps= 33 q=24.0 size=    3028kB time=00:00:05.93 bitrate=4182.4kbits/s dup=2 drop=0 speed=1.05x    
  
  frame=  205 fps= 33 q=24.0 size=    3329kB time=00:00:06.59 bitrate=4133.3kbits/s dup=2 drop=0 speed=1.07x    
  
  frame=  224 fps= 34 q=24.0 size=    3610kB time=00:00:07.23 bitrate=4089.7kbits/s dup=2 drop=0 speed=1.08x    
  
  frame=  243 fps= 34 q=24.0 size=    3901kB time=00:00:07.86 bitrate=4063.3kbits/s dup=2 drop=0 speed=1.09x    
  
  frame=  264 fps= 34 q=24.0 size=    4297kB time=00:00:08.56 bitrate=4110.6kbits/s dup=2 drop=0 speed=1.11x    
  
  frame=  284 fps= 35 q=24.0 size=    4601kB time=00:00:09.23 bitrate=4083.5kbits/s dup=2 drop=0 speed=1.12x    
  
  frame=  304 fps= 35 q=24.0 size=    4886kB time=00:00:09.89 bitrate=4044.4kbits/s dup=2 drop=0 speed=1.14x    
  
  frame=  314 fps= 35 q=-1.0 Lsize=    5138kB time=00:00:10.46 bitrate=4022.4kbits/s dup=2 drop=0 speed=1.16x    
  
  video:5135kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.040961%
  
  [libx264 @ 0xee1fdc00] frame I:2     Avg QP:20.50  size: 84700
  
  [libx264 @ 0xee1fdc00] frame P:312   Avg QP:24.06  size: 16310
  
  [libx264 @ 0xee1fdc00] mb I  I16..4: 100.0%  0.0%  0.0%
  
  [libx264 @ 0xee1fdc00] mb P  I16..4:  7.7%  0.0%  0.0%  P16..4: 54.9%  0.0%  0.0%  0.0%  0.0%    skip:37.4%
  
  [libx264 @ 0xee1fdc00] coded y,uvDC,uvAC intra: 62.7% 22.9% 3.4% inter: 26.1% 8.4% 0.9%
  
  [libx264 @ 0xee1fdc00] i16 v,h,dc,p: 13% 14% 59% 13%
  
  [libx264 @ 0xee1fdc00] i8c dc,h,v,p: 47% 24% 22%  6%
  
  [libx264 @ 0xee1fdc00] kb/s:4020.26
  
   Success
  
  time used: 9843

  So what could be the reason of such low CPU load ?