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• VBV-CBR and ABR in X264

  11 décembre 2013, par xkfz007

  In x264 VBV-CBR RC mode is based on ABR and vbv-maxrate and vbv-bufsize are set. On the basis of frame QP decided by ABR, the MB row QP is decided by VBV-CBR for each row. I test these two modes and the command lines are listed :
  ABR : -o BasketballDrill_832x480_50_20131210102507.264 BasketballDrill_832x480_50.yuv 832x480 —fps 50 —frames 300 —bitrate 1120 —profile baseline —threads -1 -I 50 -v —psnr
  VBV-CBR : -o BasketballDrill_832x480_50_20131210102507_mb.264 BasketballDrill_832x480_50.yuv 832x480 —fps 50 —frames 300 —bitrate 1120 —vbv-maxrate 1120 —vbv-bufsize 1680 —profile baseline —threads 1 -I 50 -v —psnr

  The final results are :
  ABR : Y-PSNR 31.530dB, bitrate 1146.93kbps
  VBV-CBR : Y-PSNR 31.728dB, bitrate 1230.25kbps
  Compared to ABR, VBV-CBR achieved 4.9% bitrate promotion and 0.198dB PSNR promotion. But the PSNR promotion is lower than bitrate (1% bitrate=0.05dB).

  Having talked so much, I just want to ask what is the advantage of VBV-CBR compared ABR ? If ABR can get the reasonable results, why the VBV-cBR is needed ?
  In my opinion, VBV-CBR maybe can promote the subjective quality owing to deciding the QP for each MB row. But the bitrate also rises. Also I have compared some frames of the two modes, they are almost the same.
  Maybe there are some situations that are fit for VBV-CBR and I don't know. So guys, give me, the new to x264, some professional explanation.

• How to force "full range" flag on export

  28 janvier 2019, par Emanuele Vissani

  I have an ffmpeg command to remap audio tracks to descrete channels in a ProRes 4444 quicktime file. Even if the input video is copied to the output, the exported file is interpreted by a professional video player software as video range (16-234 values) instead of the original full range (0-255 values), making it look more contrasted.
  The content is actually correct, changing manually the range setting in the player software gives back the right light range, so I think the output file just lose some kind of range flag.

  I already tried the following options without results :

  -colorspace bt709 -movflags +write_colr

  -dst_range 1 -color_range 2

  -vf scale=out_range=full

  -vf scale=in_range=full:out_range=full

  Original command is :

  ffmpeg -i F:\_IMPORT\TST_ProRes4444_4k.mov -map 0:0 -c copy -map 0:1 -c copy -map_channel 0.2.0:0.2 -c:a pcm_s24le F:\_EXPORT\TEST\test.mov

  Thank you for your help.

• Announcing Long Term Support in Piwik 2 – The analytics platform for your mission critical projects

  11 janvier 2016, par Matthieu Aubry — About, Development

  We are proud to announce our Long Term Support (LTS) for Piwik 2.X !

  Why Long Term Support (LTS) ?

  Part of our mission is to ready Piwik for the enterprise — and ready the enterprise for Piwik. Our fast release cycle and our ability to quickly innovate has served us well for the past seven years and has lead Piwik to being one of the most popular open source projects, used by over one million websites worldwide. But Piwik’s success today has also shown us that this fast release cycle is not suited for all users and customers. Like most large open source projects (such as Ubuntu, Firefox, Debian, Symfony, Node.js, etc.) at Piwik we now also offer a Long Term Support release which gives users the confidence that Piwik can be used for mission critical projects for months to come.

  What does LTS mean for Piwik ?

  For the duration of the LTS period, Piwik 2.X will continue to receive the following fixes :

  • Critical bugs causing data loss or data corruption.
  • Major and Critical security issues.

  Our goal is to offer you a Piwik LTS release that you can trust for all your mission critical projects.

  How long will Piwik 2.X be supported ?

  Piwik 2.X will be supported for at least 12 months after the initial release of Piwik 3.0.0.
  Piwik 3.0.0 is expected to be released in the second half of 2016.
  This means that Piwik 2.X will be supported at least until the second half of 2017.

  Which Piwik version is LTS ?

  The latest Piwik 2.16.X release is our Long Term Support version.

  How do I benefit from the LTS version ?

  To get the full benefits of Piwik LTS, please make sure you are using the latest LTS version. First, update to the latest Piwik 2.X version, then Configure Piwik to use the LTS release channel and then update to the latest LTS version.

  How do I configure Piwik to use the LTS version ?

  By default, Piwik will not use the LTS version. When you use the one-click update your Piwik instance will be updated to the very latest release : when Piwik 3.0.0 will be released, the one click update will update your instance to 3.0.0. It is however possible to configure your Piwik so that you will stay on Piwik 2.X and keep using the LTS Long Term Support version :

  • Login Piwik as the Super User,
  • Go to Settings > General > Update settings,
  • Under “Release channel” click “Latest stable 2.X Long Term Support version”, and click “Save”.
    

  How do I get professional Piwik Support ?

  If you need professional support for your Piwik service get in touch with the Piwik PRO experts.

  ---

  For other questions, feedback or discussion, feel free to join our forums and comment on this LTS forum post.

  We wish you all a fantastic year 2016 !