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• H.264 and VP8 for still image coding : WebP ?

  
  1er octobre 2010, par Dark Shikari — google, H.264, psychovisual optimizations, VP8

  Update : post now contains a Theora comparison as well ; see below.

  JPEG is a very old lossy image format. By today’s standards, it’s awful compression-wise : practically every video format since the days of MPEG-2 has been able to tie or beat JPEG at its own game. The reasons people haven’t switched to something more modern practically always boil down to a simple one — it’s just not worth the hassle. Even if JPEG can be beaten by a factor of 2, convincing the entire world to change image formats after 20 years is nigh impossible. Furthermore, JPEG is fast, simple, and practically guaranteed to be free of any intellectual property worries. It’s been tried before : JPEG-2000 first, then Microsoft’s JPEG XR, both tried to unseat JPEG. Neither got much of anywhere.

  Now Google is trying to dump yet another image format on us, “WebP”. But really, it’s just a VP8 intra frame. There are some obvious practical problems with this new image format in comparison to JPEG ; it doesn’t even support all of JPEG’s features, let alone many of the much-wanted features JPEG was missing (alpha channel support, lossless support). It only supports 4:2:0 chroma subsampling, while JPEG can handle 4:2:2 and 4:4:4. Google doesn’t seem interested in adding any of these features either.

  But let’s get to the meat and see how these encoders stack up on compressing still images. As I explained in my original analysis, VP8 has the advantage of H.264′s intra prediction, which is one of the primary reasons why H.264 has such an advantage in intra compression. It only has i4x4 and i16x16 modes, not i8x8, so it’s not quite as fancy as H.264′s, but it comes close.

  The test files are all around 155KB ; download them for the exact filesizes. For all three, I did a binary search of quality levels to get the file sizes close. For x264, I encoded with --tune stillimage --preset placebo. For libvpx, I encoded with --best. For JPEG, I encoded with ffmpeg, then applied jpgcrush, a lossless jpeg compressor. I suspect there are better JPEG encoders out there than ffmpeg ; if you have one, feel free to test it and post the results. The source image is the 200th frame of Parkjoy, from derf’s page (fun fact : this video was shot here ! More info on the video here.).

  Files : (x264 [154KB], vp8 [155KB], jpg [156KB])

  Results (decoded to PNG) : (x264, vp8, jpg)

  This seems rather embarrassing for libvpx. Personally I think VP8 looks by far the worst of the bunch, despite JPEG’s blocking. What’s going on here ? VP8 certainly has better entropy coding than JPEG does (by far !). It has better intra prediction (JPEG has just DC prediction). How could VP8 look worse ? Let’s investigate.

  VP8 uses a 4×4 transform, which tends to blur and lose more detail than JPEG’s 8×8 transform. But that alone certainly isn’t enough to create such a dramatic difference. Let’s investigate a hypothesis — that the problem is that libvpx is optimizing for PSNR and ignoring psychovisual considerations when encoding the image… I’ll encode with --tune psnr --preset placebo in x264, turning off all psy optimizations. 

  Files : (x264, optimized for PSNR [154KB]) [Note for the technical people : because adaptive quantization is off, to get the filesize on target I had to use a CQM here.]

  Results (decoded to PNG) : (x264, optimized for PSNR)

  What a blur ! Only somewhat better than VP8, and still worse than JPEG. And that’s using the same encoder and the same level of analysis — the only thing done differently is dropping the psy optimizations. Thus we come back to the conclusion I’ve made over and over on this blog — the encoder matters more than the video format, and good psy optimizations are more important than anything else for compression. libvpx, a much more powerful encoder than ffmpeg’s jpeg encoder, loses because it tries too hard to optimize for PSNR.

  These results raise an obvious question — is Google nuts ? I could understand the push for “WebP” if it was better than JPEG. And sure, technically as a file format it is, and an encoder could be made for it that’s better than JPEG. But note the word “could”. Why announce it now when libvpx is still such an awful encoder ? You’d have to be nuts to try to replace JPEG with this blurry mess as-is. Now, I don’t expect libvpx to be able to compete with x264, the best encoder in the world — but surely it should be able to beat an image format released in 1992 ?

  Earth to Google : make the encoder good first, then promote it as better than the alternatives. The reverse doesn’t work quite as well.

  Addendum (added Oct. 2, 03:51) :

  maikmerten gave me a Theora-encoded image to compare as well. Here’s the PNG and the source (155KB). And yes, that’s Theora 1.2 (Ptalarbvorm) beating VP8 handily. Now that is embarassing. Guess what the main new feature of Ptalarbvorm is ? Psy optimizations…

  Addendum (added Apr. 20, 23:33) :

  There’s a new webp encoder out, written from scratch by skal (available in libwebp). It’s significantly better than libvpx — not like that says much — but it should probably beat JPEG much more readily now. The encoder design is rather unique — it basically uses K-means for a large part of the encoding process. It still loses to x264, but that was expected.

  [155KB]

• Podcast Producer 2 REST api

  11 septembre 2009

  I’ve been working on documenting the REST api that PCP2 uses for client server communication as part of a new project. I thought it might be useful to other folks. Consider this a work in progress - I’ve only documented the workflow for doing a multisource recording so far. Follow the job for the info.

  Each section gives a sample command and a sample response.

  All pages are behind basic HTTP auth.

  General sequence of events

  * get workflow list
  * get cameras
  * request status for camera (including thumbnail)
  * start cameras
  * create recording enclosure
  * stop cameras, provide submission_UUID returned by above step, include title

  ---

  *URL : https://pcpserver:8170/podcastproducer/info

  *Type : GET

  *Content : version=2

  *Response :
  <pre>
  <podcast_producer_result>
  <action>index</action>
  <status>success</status>
  <plist version="1.0">
  <dict>
  <key>server_version</key>
  <string>2.0</string>
  <key>http_auth_type</key>
  <array>
  <string>basic</string>
  <string>digest</string>
  <string>kerberos</string>
  </array>
  <key>krb_service_principals</key>
  <array>
  <string>pcast/x101-186-103-dhcp.cla.umn.edu@X101-186-103-DHCP.CLA.UMN.EDU</string>
  </array>
  <key>server_uuid</key>
  <string>DB31DA49-10AE-472C-B3B9-86A8F8112399</string>
  <key>cluster_members</key>
  <dict>
  <key>F1021B98-7E7E-44FB-8EB1-E0DA1885D5BA</key>
  <dict>
  <key>date_added</key>
  <string>Tue Sep 01 10:23:49 -0500 2009</string>
  <key>last_update</key>
  <string>Tue Sep 08 10:35:17 -0500 2009</string>
  <key>server_host</key>
  <string>x101-186-103-dhcp.cla.umn.edu</string>
  <key>server_port</key>
  <string>8170</string>
  <key>tunnel_agent_host</key>
  <string>x101-186-103-dhcp.cla.umn.edu</string>
  <key>tunnel_agent_port</key>
  <string>8175</string>
  <key>network_addrs</key>
  <array>
  <string>128.101.186.103</string>
  </array>
  </dict>
  </dict>
  </dict>
  </plist>
  </podcast_producer_result>
  </pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/workflows
  * Type : GET
  * Content : version=2&language=en
  * Response :
  <pre>
  <podcast_producer_result>
  <action>index</action>
  <status>success</status>
  <results>OK</results>
  <plist version="1.0">
  <dict>
  <key>user_fullname</key>
  <string>podcast</string>
  <key>user_shortname</key>
  <string>podcast</string>
  <key>workflows</key>
  <array>
  <dict>
  <key>name</key>
  <string>Montage</string>
  <key>title</key>
  <string>Montage</string>
  <key>description</key>
  <string>Montage workflow</string>
  <key>uuid</key>
  <string>F797D54D-1539-42AA-B6AC-3CB3A4C15EF5</string>
  <key>version</key>
  <string>2.0</string>
  <key>editor</key>
  <string>Podcast Composer</string>
  <key>sources</key>
  <array>
  <dict>
  <key>contentTypes</key>
  <array>
  <string>com.apple.quicktime-movie</string>
  <string>com.adobe.pdf</string>
  <string>com.apple.iwork.keynote.key</string>
  <string>com.apple.iwork.pages.pages</string>
  <string>org.openxmlformats.wordprocessingml.document</string>
  <string>com.microsoft.word.doc</string>
  <string>org.openxmlformats.presentationml.presentation</string>
  <string>com.microsoft.powerpoint.ppt</string>
  <string>com.microsoft.bmp</string>
  <string>com.compuserve.gif</string>
  <string>public.jpeg-2000</string>
  <string>public.jpeg</string>
  <string>com.adobe.pdf</string>
  <string>com.apple.pict</string>
  <string>public.png</string>
  <string>com.adobe.photoshop-image</string>
  <string>com.sgi.sgi-image</string>
  <string>com.truevision.tga-image</string>
  <string>public.tiff</string>
  </array>
  <key>description</key>
  <string>Any Document</string>
  <key>isFolder</key>
  <true/>
  <key>isOptional</key>
  <false/>
  <key>sourceTypes</key>
  <array>
  <string>File</string>
  </array>
  </dict>
  </array>
  <key>user_requirements</key>
  <array>
  <string>Title</string>
  <string>Description</string>
  </array>
  <key>access_control_entries</key>
  <array>
  </array>
  </dict>
  <dict>
  <key>name</key>
  <string>Single Source</string>
  <key>title</key>
  <string>Single Source</string>
  <key>description</key>
  <string>Single Source workflow</string>
  <key>uuid</key>
  <string>DEFA1587-A650-426E-92DA-01C5EB811705</string>
  <key>version</key>
  <string>2.0</string>
  <key>editor</key>
  <string>Podcast Composer</string>
  <key>sources</key>
  <array>
  <dict>
  <key>contentTypes</key>
  <array>
  <string>com.apple.quicktime-movie</string>
  </array>
  <key>description</key>
  <string>Any Video</string>
  <key>isFolder</key>
  <false/>
  <key>isOptional</key>
  <false/>
  <key>sourceTypes</key>
  <array>
  <string>Video</string>
  <string>Screen</string>
  <string>Audio</string>
  <string>File</string>
  </array>
  </dict>
  </array>
  <key>user_requirements</key>
  <array>
  <string>Title</string>
  <string>Description</string>
  </array>
  <key>access_control_entries</key>
  <array>
  </array>
  </dict>
  </array>
  </dict>
  </plist>
  </podcast_producer_result>
  </pre>
  ----

  * URL : https://pcpserver:8170/podcastproducer/cameras
  * Type : GET
  * Content : version=2
  * Response :
  <pre>
  <podcast_producer_result>
  <action>index</action>
  <status>success</status>
  <plist version="1.0">
  <dict>
  <key>cameras</key>
  <array>
  <dict>
  <key>name</key>
  <string>150-A Camera</string>
  <key>uuid</key>
  <string>307682A5-B552-4AFA-B7E2-3811D772C9A1</string>
  <key>connected_to_member_uuid</key>
  <string>F1021B98-7E7E-44FB-8EB1-E0DA1885D5BA</string>
  <key>in_use</key>
  <string>false</string>
  <key>recording_status</key>
  <string>online</string>
  <key>preview_url</key>
  <string>https://x101-186-103-dhcp.cla.umn.edu:8170/podcastproducer/previews/307682A5-B552-4AFA-B7E2-3811D772C9A1.jpg</string> ;
  <key>access_control_entries</key>
  <array>
  </array>
  </dict>
  <dict>
  <key>name</key>
  <string>150-A Epiphan</string>
  <key>uuid</key>
  <string>CE610AB0-CA50-49EB-8FFE-78E57CDCA550</string>
  <key>connected_to_member_uuid</key>
  <string>F1021B98-7E7E-44FB-8EB1-E0DA1885D5BA</string>
  <key>in_use</key>
  <string>false</string>
  <key>recording_status</key>
  <string>online</string>
  <key>preview_url</key>
  <string>https://x101-186-103-dhcp.cla.umn.edu:8170/podcastproducer/previews/CE610AB0-CA50-49EB-8FFE-78E57CDCA550.jpg</string> ;
  <key>access_control_entries</key>
  <array>
  </array>
  </dict>
  </array>
  </dict>
  </plist>
  </podcast_producer_result>
  </pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/cameras/start
  * Type : POST
  * Content : action=pause&version=2&camera_name=150-A%20Camera&controller=cameras
  * Response :
  <pre>
  <podcast_producer_result>
  <action>start</action>
  <status>success</status>
  <results>OK</results>
  </podcast_producer_result>
  </pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/cameras/status
  * Type : POST
  * Content : delay=0&action=start&version=2&camera_name=150-A%20Epiphan&controller=cameras
  * Response :
  <pre><podcast_producer_result>
  <action>status</action>
  <status>success</status>
  <results>OK</results>
  <plist version="1.0">
  <dict>
  <key>preview</key>
  <string>https://x101-186-103-dhcp.cla.umn.edu:8170/podcastproducer/previews/307682A5-B552-4AFA-B7E2-3811D772C9A1.jpg</string> ;
  <key>preview_image_data</key>
  <string>RAW JPEG DATA RAW JPEG DATA RAW JPEG DATA RAW JPEG DATA RAW JPEG DATA</string>
  <key>recording_status</key>
  <string>online</string>
  <key>started_at</key>
  <string>Tue Sep 08 09:31:40 -0500 2009</string>
  <key>stopped_at</key>
  <string>Tue Sep 08 09:32:10 -0500 2009</string>
  <key>elapsed</key>
  <string>41</string>
  <key>last_error</key>
  <string>805306368</string>
  </dict>
  </plist>
  </podcast_producer_result>
  </pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/cameras/pause
  * Type : POST
  * Content : action=pause&version=2&camera_name=150-A%20Camera&controller=cameras
  * Response :
  <pre><podcast_producer_result>
  <action>status</action>
  <status>success</status>
  <results>OK</results>
  <plist version="1.0">
  <dict>
  <key>preview</key>
  <string>https://x101-186-103-dhcp.cla.umn.edu:8170/podcastproducer/previews/307682A5-B552-4AFA-B7E2-3811D772C9A1.jpg</string> ;
  <key>recording_status</key>
  <string>online</string>
  <key>started_at</key>
  <string>Tue Sep 08 09:31:40 -0500 2009</string>
  <key>stopped_at</key>
  <string>Tue Sep 08 09:32:10 -0500 2009</string>
  <key>elapsed</key>
  <string>41</string>
  <key>last_error</key>
  <string>805306368</string>
  </dict>
  </plist>
  </podcast_producer_result></pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/cameras/stop
  * Type : POST
  * Content : workflow_name=&UserMetadata_Description=&submission_uuid=7497E3AC-0A75-4C7C-8C66-26294C9274FE&action=stop&version=2&camera_name=150-A%20Epiphan&controller=cameras&UserMetadata_Title=Test123
  * Response :
  <pre><podcast_producer_result>
  <action>stop</action>
  <status>success</status>
  <results>OK</results>
  </podcast_producer_result>
  </pre>

  ---

  * URL : https://pcpserver:8170/podcastproducer/recordings/create
  * Type : POST
  * Content : version=2&workflow_uuid=C6EF52A7-04E3-477D-9F38-6B61F108D7B9
  * Response :
  <pre>
  <podcast_producer_result>
  <action>create</action>
  <status>success</status>
  <results>OK</results>
  <plist version="1.0">
  <dict>
  <key>workflow_uuid</key>
  <string>C6EF52A7-04E3-477D-9F38-6B61F108D7B9</string>
  <key>recording_uuid</key>
  <string>FD5A1459-F7CE-41FA-8155-049DF774298B</string>
  <key>submission_uuids</key>
  <array>
  <string>A626D8E4-E439-4E57-9982-DB4BD035CB41</string>
  <string>CFBCCB74-A41F-42D3-BEAA-58165B1116C6</string>
  </array>
  </dict>
  </plist>
  </podcast_producer_result>
  </pre>

• Data Privacy Day 2020

  27 janvier 2020, par Matthieu Aubry — Privacy
  It’s January 28th which means it’s Data Privacy Day !

  Today is an important day for the Matomo team as we reflect on our mission and our goals for 2020. This year I wanted to send a video message to all Matomo users, community members and customers. 

  Check it out (full transcript below)

  

  A video message from Matomo founder, Matthieu Aubry

  Privacy-friendly alternatives

  • NoMoreGoogle :
    a comprehensive list giving you options for other privacy-friendly alternatives.
  • Switching.Software :
    Ethical alternatives to popular sites and apps.
  • Web browser :
    Firefox
    Brave
    Vivaldi
  • Search engine :
    DuckDuckGo
    Qwant
  • File sharing :
    Nextcloud
  • Email provider :
    ProtonMail
    Mailfence
    Tutanota

  Video transcript

  Hey everyone,

  Matthieu here, Founder of Matomo.

  Today is one of the most significant days of the year for the Matomo team – it’s Data Privacy Day. And so I wanted to quickly reflect on our mission and the significance of this day. 

  In today’s busy online world where data is king, this day is an important reminder of being vigilant in protecting our personal information online.

  Matomo began 12 years ago as an open-source alternative to Google Analytics – the goal was, and still is to give full control of data back to users. 

  In 2020, we are determined to see through this commitment. We will keep building a powerful and ethical web analytics platform that focuses on privacy protection, data ownership, and provides value to all Matomo users and customers.

  And what’s fantastic is to see the rise of other quality software companies offering privacy-friendly alternatives for web browsers, search engines, file sharing, email providers, all with a similar mission. And with these products now widely available, we encourage you to take back control of all your online activities and begin this new decade with a resolution to stay safe online.

  I’ll provide you with some links below the video to check out these privacy-friendly alternatives. If you have a website and want to gain valuable insights on the visitors while owning your data, join us ! 

  Matomo Analytics On-Premise is and always will be free to download and install on your own servers and on your own terms.

  Also feel free to join our active community or spread the word to your friends and network about the importance of data privacy.

  Thank you all and wishing you a great 2020 !

  For more information on how Matomo protects the privacy of your users, visit : https://matomo.org/privacy/

  Do you have privacy concerns ?

  What better day than today to speak up ! What privacy concerns have you experienced ?

  Contact Support